Kinetic and Potential Energy: a full term of science
Ten ready-to-teach lessons for Year 8 Physical sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards, an evidence sheet or exit tickets, an assessment kit and worked answers.
Start here: five minutes to Monday
- Skim the term at a glance on the next page.
- Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, and cards, an evidence sheet or tickets.
- Gather the few items under “You need” on the plan. Most come from the science prep room, a toy box or a hardware store.
- Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
- Teach straight from the plan. Timings, talk prompts, misconceptions and worked answers are all on the one page.
For any Year 8 science teacher
The pack suits a physics specialist and a teacher working outside their own subject alike: each plan explains the idea in plain words, lists the misconceptions students bring, and gives worked answers. The big idea of the term: energy is never made or destroyed. It is stored as potential energy and shows itself as kinetic energy; it moves from object to object and changes from form to form; and at every step some of it spreads out as heat and sound, which is why machines are never perfectly efficient.
Two ways to run each lesson
Every lesson works as one 60-minute block, or as two 30-minute sessions; the split point is marked in every plan. Look ahead: Lesson 5 needs foam pipe insulation from a hardware store, Lesson 7 needs six stations set up before the class arrives, and Lesson 9 needs a box of dominoes or blocks.
Safety and care in one look
Eye protection goes on whenever rubber bands are stretched, and nothing is launched towards anyone. Spilt flour is swept up straight away. Filament and halogen globes get very hot, so students feel their warmth from a distance and never touch them.
The term at a glance
One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.
| # | Lesson | Students learn and do | You need (in short) |
|---|---|---|---|
| 1 | Kinetic or potential? | Sort twelve energy cards into the two families and name the form of energy on each | The energy cards, a ball, a rubber band |
| 2 | Height stores energy | Drop a ball into flour from five heights, graph the craters, and calculate gravitational potential energy | Flour trays, a ball, metre rulers |
| 3 | Mass, speed and kinetic energy | Roll a toy car down a ramp into a cup, double its mass, and see why speed counts twice; read braking distances | Ramps, toy cars, paper cups |
| 4 | Where does the energy go? | Video two balls bouncing, work out the share of height kept each bounce, and follow the missing energy | Two balls, a metre ruler, a phone |
| 5 | Swings and roller coasters | Build a marble track, find the highest hill a marble can climb, and match energy bar cards to a track | Foam pipe insulation, marbles, the bar cards |
| 6 | Stretch and release | Launch a car with a rubber band at four stretches and find the square pattern | Rubber bands, toy cars, eye protection |
| 7 | Energy passing through systems | Visit six energy stations and draw flow diagrams with a system boundary | The six stations and their cards |
| 8 | Useful and wasted energy | Compare five devices, calculate efficiency, and draw Sankey diagrams to scale | Rulers, coloured pencils, two lamps |
| 9 | A chain-reaction machine | Design, build and improve a machine with at least four energy transformations | Dominoes, marbles, rulers, tape |
| 10 | Show what we know | Track a skater’s energy on a half-pipe, sit the final check and play the class quiz | The task and check, the interactive unit |
How the sequence builds
Lesson 1 sorts energy into its two families. Lessons 2 and 3 measure and calculate the two energies that matter most in motion, gravitational potential and kinetic. Lessons 4 to 6 follow energy as it changes between them, in bounces, swings, tracks and stretched bands, and meet conservation. Lessons 7 and 8 trace energy through systems and count what is wasted, Lesson 9 puts it all into a machine, and Lesson 10 brings it together.
Curriculum links (Australian Curriculum V9)
The whole term teaches the Science Understanding descriptor AC9S8U05 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:
Assessment in this pack
- Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 8 voice, with working.
- The assessment sheet near the front has a class observation checklist and a three-level rubric.
- Lesson 10 is the summative pair: the half-pipe task, plus the “Show what we know” check.
Materials for the whole term
One gathering session covers all ten lessons. Most of it comes from the science prep room, a toy box and a hardware store. Two things are worth doing ahead: buy the foam pipe insulation for Lesson 5, and set out the six stations for Lesson 7 before the class arrives.
| Lesson | You need |
|---|---|
| 1 | the energy cards from this pack, one set per pair; a ball, a rubber band and a muesli bar to show |
| 2 | for each group: a deep tray with about 3 cm of plain flour, a ball of about 50 g, a metre ruler, a short ruler and a spoon; cocoa to dust the flour |
| 3 | for each group: a ramp about 1 m long, books, a toy car of about 100 g, a paper cup with a doorway cut in its rim, a tape measure, coins or plasticine and a balance |
| 4 | for each group: a tennis ball, a rubber bouncy ball, a metre ruler taped to a wall and a phone to video the bounces |
| 5 | for each group: 2 m of foam pipe insulation cut in half along its length, masking tape, a marble and a metre ruler; a pendulum on a 1.5 m string; the bar cards from this pack |
| 6 | for each group: a wide rubber band, two chair legs or pegs, a toy car, a ruler taped to the floor, a tape measure and eye protection |
| 7 | six stations: a torch, a wind-up toy, a ball and a metal tray, a small solar fan and a desk lamp, a battery fan; the station cards from this pack |
| 8 | rulers and coloured pencils; two desk lamps of about the same brightness, one with a filament or halogen globe and one with an LED globe, if you have them |
| 9 | for each team: dominoes or blocks, marbles, a toy car, books, rulers, cardboard tubes, string, paper cups, rubber bands and masking tape |
| 10 | the task and the final check, calculators; the interactive unit open for the class quiz |
The one-trip list
- From the prep room: metre rulers, balances, eye protection, a desk lamp, a small solar fan or a solar cell and motor.
- From a toy box: toy cars, marbles, a wind-up toy, a tennis ball, a rubber bouncy ball and dominoes or blocks.
- From the supermarket: plain flour, cocoa, paper cups, rubber bands, a muesli bar and a battery fan.
- From a hardware store: foam pipe insulation, masking tape and string; a torch if the school has none.
Safety and care in one look
- Eye protection whenever rubber bands are stretched; launches go along the floor, never towards people.
- Flour trays sit on the floor, and spills are swept up straight away.
- Filament and halogen globes get very hot: feel the warmth from about 10 cm away, and never touch.
- Balls are dropped, not thrown, and the lamp cords stay tidy.
Assessment without extra work
The term assesses itself. Every lesson plan ends with worked answers and look-fors, and Lesson 10 is the summative pair: the half-pipe task, in which students track a skater’s energy and account for the part that is wasted, and the final check. This sheet is the place to note what you see along the way.
The three levels
| Idea | Working towards | At standard | Beyond |
|---|---|---|---|
| Kinetic and potential | says whether something is moving | classifies forms of energy as kinetic or potential, including heat and sound, with reasons | explains why one object can have both at once, as in a swing or a thrown ball |
| Calculating energy | says what the energy depends on | calculates gravitational potential and kinetic energy with the right units | uses the square of the speed or the stretch to predict a result |
| Transfer and transformation | names the energy at the start and the end | draws flow diagrams that show transfers and transformations through a system | chooses a system boundary and explains what crosses it |
| Conservation and waste | says energy goes somewhere | explains that energy is conserved, accounts for wasted energy and calculates efficiency | uses Sankey diagrams to compare devices and argue for a choice |
| Working scientifically | records results in a table | controls variables, takes means and graphs results | recognises a curved pattern and explains the limits of the measurements |
Class observation checklist
| Name | Families | Calculating | Flows | Conserved | Investigating |
|---|---|---|---|---|---|
A tick a lesson is plenty; the Lesson 10 task and check fill the gaps.
Word wall cards
Cut out the cards and build the wall as the words arrive: energy, joule, kinetic energy, potential energy and thermal energy in Lesson 1; gravitational potential energy in Lesson 2; friction in Lesson 3; energy transfer, energy transformation and conservation of energy in Lesson 4; elastic potential energy and chemical potential energy in Lesson 6; system and energy flow diagram in Lesson 7; useful energy, wasted energy, efficiency and Sankey diagram in Lesson 8.
what is needed to make something move, warm up, light up or make a sound
the unit of energy
the energy of a moving object, or of the moving particles inside it
stored energy, waiting to be released
the kinetic energy of the particles in a substance; we feel it as heat
energy stored by lifting an object against gravity
a force between surfaces that turns kinetic energy into heat
energy moving from one object or place to another
energy changing from one form into another
energy is never made or destroyed; the total stays the same
energy stored in a stretched or squashed object
energy stored in food, fuels and batteries
the set of parts we choose to study together
a diagram of boxes and arrows that shows how energy changes form
the energy that comes out in the form we want
energy that spreads into the surroundings, usually as heat and sound
useful energy out divided by energy in, as a percentage
a flow diagram drawn with bands as wide as the amounts of energy
Dear families
This term in science, Year 8 studies energy: the two big families, kinetic and potential; how energy moves from object to object and changes from form to form; and why it is never destroyed, even when it seems to disappear. Students learn to calculate energy, to draw the flow of energy through a system, and to judge how efficient a device is.
Along the way your student will drop balls into flour, crash toy cars into paper cups, film bouncing balls, build a marble roller coaster, launch cars with rubber bands, and design a chain-reaction machine.
Try this at home
- Drop a ball and count the bounces. Why does each bounce come up a little lower?
- On a swing, notice where you move fastest and where you stop for a moment.
- Feel a phone charger or a laptop after it has been working. Where is the warmth coming from?
- Look for the energy rating label on a fridge or a washing machine. What does it tell a buyer?
What to ask your scientist
- What are the two families of energy? Which one is a hot cup of tea in?
- Why does a ball never bounce back up to where you dropped it?
- Why is a crash at 60 km/h so much worse than one at 30 km/h?
- What does it mean when a light globe is more efficient?
A small note on care: students wear eye protection when they stretch rubber bands, nothing is launched towards anyone, and hot globes are felt from a distance, never touched.
Warm regards,
The Year 8 science team
Printed from the free seegongsik Kinetic and Potential Energy teaching pack · seegongsik.com/au/y8/physical/AC9S8U05/pack
Kinetic or potential?
Energy is what makes things happen: it is needed to make something move, warm up, light up or make a sound. It is measured in joules (J); lifting an apple from the floor onto a desk takes about one joule. Every form of energy in this unit belongs to one of two families. Kinetic energy is the energy of movement, of a whole object or of the particles inside it, so heat (thermal energy) and sound count as kinetic. Potential energy is stored energy: gravitational (from height), elastic (from a stretch or a squash) and chemical (in food, fuel and batteries). Light and electrical energy do not sort neatly at this level, so this lesson leaves them for Lessons 7 and 8. Pairs sort twelve energy cards into the two families.
We are learning to
- describe energy as what is needed to make things change, measured in joules,
- classify forms of energy as kinetic or potential,
- give a reason for each choice.
Success criteria
- I can sort the twelve cards and name the form of energy on each.
- I can explain why heat and sound count as kinetic energy.
You need
- the energy cards (third sheet), one set per pair, and the worksheet (next sheet), one per student,
- to show: a ball, a rubber band and a muesli bar.
Lesson flow (about 60 minutes)
| 5 min | Three objects Drop the ball, stretch the band, and hold up the muesli bar. Ask: “Which of these has energy right now? Which could have energy in a moment?” |
| 10 min | On the board Show the board (see the box). Add energy, joule, kinetic energy, potential energy and thermal energy to the word wall. |
| 20 min | Twelve cards Pairs lay down the two grey heading cards, sort the twelve cards and record each one in Part A with its form of energy. Ask: “Which card did you argue about? What settled it?” |
| 10 min | Two hard ones Take cards G (the hot tea) and D (the drum) as a class. Ask what is moving in each: the particles of the tea, and the air particles carrying the sound. |
| 15 min | The two families Students list the forms in each family in Part B and answer Part C. |
Running two half-sessions instead? Do the opening, the board and the cards in Session A, and the two hard ones, Part B and Part C in Session B.
Watch for these ideas
- “Only moving things have energy.” A still object can store energy in its height, its stretch or its chemicals.
- “Heat is a substance that flows into things.” Heat is energy; the particles of a hot object move faster.
- “Energy gets used up.” Energy moves from place to place and changes form, but it is never destroyed; Lesson 4 comes back to this.
Make it easier, make it bigger
- Easier: sort cards A to F first, then add the rest.
- Bigger: a pendulum swings back and forth. Where in its swing is its kinetic energy greatest, and where is its potential energy greatest?
Answers and look-fors
- Part A: A kinetic (movement), B potential (elastic), C kinetic (movement), D kinetic (sound), E potential (chemical), F potential (gravitational), G kinetic (thermal), H kinetic (movement), I potential (chemical), J potential (gravitational), K kinetic (movement), L kinetic (movement).
- Part B: kinetic: movement, sound, thermal; potential: elastic, chemical, gravitational.
- Part C: 1. Its particles are moving quickly; the hotter the tea, the faster they move, so thermal energy is kinetic energy of particles. 2. As the water falls through the dam, its gravitational potential energy becomes kinetic energy (and, in a power station, electrical energy). 3. Both store chemical potential energy, released by chemical reactions: digestion and respiration in the body, and reactions in the battery. 4. Both: it is moving (kinetic) and it is above the ground (gravitational potential); as it rises it slows, so kinetic becomes potential.
- Bigger: kinetic is greatest at the bottom of the swing, where it moves fastest; potential is greatest at each end, where it is highest and stops for a moment.
Kinetic or potential?
A. Twelve cards
| Card | Kinetic or potential? | Form of energy |
|---|---|---|
| A | ||
| B | ||
| C | ||
| D | ||
| E | ||
| F | ||
| G | ||
| H | ||
| I | ||
| J | ||
| K | ||
| L |
B. The two families
List the forms of energy from your cards under their family.
| Kinetic energy | Potential energy |
|---|---|
C. Questions
Kinetic or potential?
Cut out the cards. Lay down the two grey heading cards, read each card, and sort it.
Teacher note: the piles are not the same size; the answer is on the plan.
Height stores energy
Lifting an object stores gravitational potential energy. The heavier the object and the higher it is lifted, the more energy is stored: on Earth, gravitational potential energy (J) = mass (kg) × 9.8 × height (m), where 9.8 is the pull of gravity on each kilogram, in newtons. When the object falls, the stored energy becomes kinetic energy, and when it lands, the kinetic energy pushes things aside and becomes heat and sound. Groups drop a ball into flour from five heights and measure the craters, then work out the energy stored in four lifts.
We are learning to
- explain what gravitational potential energy depends on,
- calculate gravitational potential energy from mass and height,
- use the size of a crater to compare amounts of energy.
Success criteria
- I can graph crater size against drop height and describe the pattern.
- I can calculate gravitational potential energy, and show that doubling the mass or the height doubles it.
You need
- for each group: a deep tray with about 3 cm of plain flour, a ball of about 50 g (a golf ball is close), a metre ruler, a short ruler and a spoon to smooth the flour,
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Safety: put the trays on the floor and sweep up spilt flour straight away, so no-one slips. A light dusting of cocoa on top makes the craters easier to see.
Lesson flow (about 60 minutes)
| 5 min | Lift a book Lift a book slowly from the floor onto a high shelf. Ask: “I used energy to lift this book. Where is that energy now?” |
| 10 min | On the board Show the board (see the box). Add gravitational potential energy to the word wall. |
| 25 min | Craters Groups drop the ball three times from each height, measure the width of each crater, smooth the flour, and record in Part A. Ask: “Measure the crater across its widest part, every time. Why does that matter?” |
| 20 min | Working out the energy Show how to use the formula on the first lift in Part C. Students graph Part B, then finish Part C and Part D. |
Running two half-sessions instead? Do the opening, the board and the craters in Session A, and the graph and the calculations in Session B.
Watch for these ideas
- “Heavier balls fall faster.” Without much air resistance, heavy and light balls fall together; the heavier one has more energy because it has more mass.
- “Only the height matters.” The energy stored depends on the mass as well as the height.
- “The energy disappears when the ball lands.” It pushes the flour aside and becomes heat and sound.
Make it easier, make it bigger
- Easier: work out the first two lifts in Part C together, with the numbers written into the formula.
- Bigger: the water in a dam falls 50 m to the turbines. How much energy does each kilogram of water carry? Each tonne?
Answers and look-fors
- Part A, example class: 20 cm 28 mm, 40 cm 34 mm, 60 cm 38 mm, 80 cm 41 mm, 100 cm 44 mm. The higher the drop, the wider the crater, but the crater grows more slowly than the height: 5 times the height gives about 1.6 times the width.
- Part B: a curve that rises steeply at first and then flattens.
- Part C: 0.5 × 9.8 × 2 = 9.8 J; 1 × 9.8 × 2 = 19.6 J; 0.5 × 9.8 × 4 = 19.6 J; 60 × 9.8 × 10 = 5880 J. Doubling the mass doubles the energy; so does doubling the height.
- Part D: 1. At 20 cm: 0.05 × 9.8 × 0.2 = 0.1 J; at 100 cm: 0.49 J, 4.9 times as much. 2. A higher drop stores more energy, so the ball is moving faster with more kinetic energy when it hits, and pushes more flour aside. 3. Repeats show up an odd result, such as a drop that hit a lump, and the mean is more reliable than one drop.
- Bigger: 1 × 9.8 × 50 = 490 J for each kilogram; 490000 J (about half a million joules) for each tonne.
- Exit tickets: 1. The same, 19.6 J each. 2. 0.2 × 9.8 × 3 = 5.88 J. 3. It becomes kinetic energy as the apple falls, then heat and sound when it lands.
Height stores energy
A. Craters in flour (width in mm)
| Drop height (cm) | Drop 1 | Drop 2 | Drop 3 | Our mean | Example class mean |
|---|---|---|---|---|---|
| 20 | 28 | ||||
| 40 | 34 | ||||
| 60 | 38 | ||||
| 80 | 41 | ||||
| 100 | 44 |
B. Graph
Plot the example class means (or your own), and draw a smooth curve through the points.
C. Working out the energy
Gravitational potential energy (J) = mass (kg) × 9.8 × height (m)
| Lift | Energy stored (J), with working |
|---|---|
| A 0.5 kg book lifted onto a 2 m shelf | |
| A 1 kg book lifted onto the same shelf | |
| The 0.5 kg book lifted onto a 4 m ledge | |
| A 60 kg diver at the top of the 10 m board |
D. Questions
Exit tickets
Cut out one ticket for each student.
1. Which stores more energy: a 2 kg pot on a 1 m bench, or a 1 kg pot on a 2 m shelf?
2. Work out the energy stored in a 0.2 kg apple 3 m up a tree.
3. What happens to that energy when the apple falls?
1. Which stores more energy: a 2 kg pot on a 1 m bench, or a 1 kg pot on a 2 m shelf?
2. Work out the energy stored in a 0.2 kg apple 3 m up a tree.
3. What happens to that energy when the apple falls?
1. Which stores more energy: a 2 kg pot on a 1 m bench, or a 1 kg pot on a 2 m shelf?
2. Work out the energy stored in a 0.2 kg apple 3 m up a tree.
3. What happens to that energy when the apple falls?
1. Which stores more energy: a 2 kg pot on a 1 m bench, or a 1 kg pot on a 2 m shelf?
2. Work out the energy stored in a 0.2 kg apple 3 m up a tree.
3. What happens to that energy when the apple falls?
Mass, speed and kinetic energy
A moving object’s kinetic energy depends on its mass and its speed: kinetic energy (J) = ½ × mass (kg) × speed × speed, with the speed in metres per second. Doubling the mass doubles the energy, but doubling the speed multiplies it by four, because the speed counts twice. Groups roll a toy car down a ramp from four heights into a paper cup, and use how far the cup is pushed as a measure of the car’s energy; then they double the car’s mass. The speeds from a phone video show the square rule, and an evidence sheet on braking distances shows why it matters on the road.
We are learning to
- explain what kinetic energy depends on,
- compare kinetic energies with a fair test,
- explain why speed matters more than mass.
Success criteria
- I can show from the results that doubling the mass about doubles the energy.
- I can explain why twice the speed means four times the energy, using the ramp or the braking data.
You need
- for each group: a ramp about 1 m long, books to prop it, a toy car of about 100 g, a paper cup with a doorway cut in its rim, a ruler and a tape measure, coins or plasticine to double the car’s mass, and a balance,
- the worksheet (next sheet) and the braking evidence sheet (third sheet), one each per student.
Set the cup upside down at the foot of the ramp with its doorway facing the car, and put it back on the same mark before every run.
Lesson flow (about 60 minutes)
| 5 min | Slow and fast Roll a ball gently into an empty cup, then roll it hard. Ask: “Which ball had more energy? How could we measure the difference?” |
| 10 min | On the board Show the board (see the box). Add friction to the word wall. |
| 25 min | Ramp runs Groups run the car three times from each height and measure how far the cup moves, then double the car’s mass and run it from 20 cm. They record beside the example class in Part A. Ask: “What must stay the same in every run for the test to be fair?” |
| 20 min | Speed counts twice Students draw the graph in Part B and work through Part C; then the braking evidence sheet. |
Running two half-sessions instead? Do the opening, the board and the ramp runs in Session A, and the graph, Part C and the evidence sheet in Session B.
Watch for these ideas
- “Twice as fast means twice the energy.” The speed counts twice, so twice as fast means four times the energy.
- “The heavier car went further because it rolled faster.” From the same height both cars reach about the same speed; the heavier car carries more energy because of its mass.
- “The energy is used up when the cup stops.” Friction between the cup and the floor turns it into heat, with a little sound.
Make it easier, make it bigger
- Easier: test only 10 cm and 40 cm, and the doubled mass.
- Bigger: work out the car’s gravitational potential energy at the top of the 40 cm ramp and its kinetic energy at the bottom. Why are they not equal?
Answers and look-fors
- Part A, example class means: 10 cm 6.1 cm, 20 cm 12.0 cm, 30 cm 18.0 cm, 40 cm 23.9 cm; doubled mass from 20 cm 24.1 cm, about twice 12.0 cm. The cup distance grows in step with the ramp height: each extra 10 cm of height adds about 5.9 cm.
- Part B: points close to a straight line through the origin.
- Part C: kinetic energy = ½ × 0.1 × speed × speed: 1.3 m/s 0.08 J, 1.9 m/s 0.18 J, 2.3 m/s 0.26 J, 2.7 m/s 0.36 J. From 10 cm to 40 cm the speed goes up about 2.1 times, the energy about 4.3 times, and the cup distance about 3.9 times.
- Part D: 1. Doubling the speed: it about quadruples the energy, where doubling the mass only doubles it. 2. So that the only thing changing is the variable we are testing; a different cup or floor would change the friction. 3. The truck: same speed, but much more mass.
- Bigger: at the top, 0.1 × 9.8 × 0.4 = 0.39 J; at the bottom, 0.36 J. About 0.03 J became heat and sound through friction on the ramp.
- Evidence sheet: 1. Four times as far (5 m to 20 m). 2. Nine times as far (5 m to 45 m). 3. Kinetic energy grows with the square of the speed, and the brakes turn it into heat at about the same rate for each metre, so four times the energy takes four times the distance. 4. At 40 km/h the braking distance is about 8.9 m, less than half of 20 m, and a car that does hit someone carries less than half the energy.
Mass, speed and kinetic energy
A. Ramp runs (distance the cup moves, in cm)
| Ramp height | Example class, three trials | Example mean | Our mean |
|---|---|---|---|
| 10 cm | 5.8, 6.3, 6.1 | ||
| 20 cm | 12.4, 11.6, 12.0 | ||
| 30 cm | 17.5, 18.4, 18.0 | ||
| 40 cm | 23.1, 24.6, 24.0 | ||
| 20 cm, mass doubled | 23.6, 24.4, 24.2 |
B. Graph
Plot the means for the car with its usual mass.
C. Speed counts twice
A phone video gave the car’s speed at the bottom of the ramp. Kinetic energy (J) = ½ × 0.1 × speed × speed.
| Ramp height | Speed (m/s) | Kinetic energy (J) |
|---|---|---|
| 10 cm | 1.3 | |
| 20 cm | 1.9 | |
| 30 cm | 2.3 | |
| 40 cm | 2.7 |
D. Questions
Why speed matters on the road
When a driver brakes, the brakes turn the car’s kinetic energy into heat. The table shows how far a typical car travels on a dry road after the brakes go on.
| Speed (km/h) | Braking distance (m) |
|---|---|
| 30 | 5 |
| 60 | 20 |
| 90 | 45 |
Real stopping distances are longer: the car also travels while the driver reacts, before the brakes go on.
Where does the energy go?
Energy is conserved: it is never made or destroyed, only transferred from one object to another or transformed from one form to another. A dropped ball shows it. Its gravitational potential energy becomes kinetic energy as it falls; as it hits the floor it squashes and stores elastic energy for an instant, which pushes it back up. But some of the energy becomes heat in the ball and the floor, and sound, so each bounce is lower than the last. For a given ball the share kept each bounce stays about the same. Groups video two kinds of ball bouncing, measure each bounce, and track where the energy goes.
We are learning to
- describe the energy changes in a bouncing ball,
- explain that energy is conserved even when it seems to disappear,
- calculate the percentage of height a ball keeps each bounce.
Success criteria
- I can draw a flow diagram for one bounce, including the energy that becomes heat and sound.
- I can work out the share of height a ball keeps each bounce, and compare two balls.
You need
- for each group: a tennis ball and a rubber bouncy ball, a metre ruler taped upright against a wall on a hard floor, and a phone to video the bounces (slow motion helps),
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Lesson flow (about 60 minutes)
| 5 min | Drop and listen Drop a ball from head height and let it bounce until it stops. Ask: “Why does it never come back up to my hand? Listen as it bounces: what do you hear?” |
| 10 min | On the board Show the board (see the box). Add energy transfer, energy transformation and conservation of energy to the word wall. |
| 25 min | Bounce by bounce Groups drop each ball from 100 cm beside the ruler, video it, and step through the video to read the top of four bounces. They record in Part A. Ask: “Read the bottom of the ball against the ruler each time. Why?” |
| 20 min | Following the energy Students graph both balls in Part B, work out the shares in Part C, and answer Part D. |
Running two half-sessions instead? Do the opening, the board and the videos in Session A, and Parts B to D in Session B.
Watch for these ideas
- “The ball runs out of energy, so energy gets used up.” It is transferred to the floor and the air as heat and sound; the total stays the same.
- “Squashing the ball wastes energy.” The squash stores elastic energy for an instant, and that is what pushes the ball back up.
- “It stops because gravity wins in the end.” Gravity pulls just as hard every bounce; each landing turns some kinetic energy into heat and sound, so less is left to lift it.
Make it easier, make it bigger
- Easier: use one ball and two bounces, and work out the share for the first bounce only.
- Bigger: a ball keeps 80% of its height each bounce. Dropped from 100 cm, after how many bounces is it below 10 cm?
Answers and look-fors
- Part B: both curves fall, steeply at first and then more gently; the tennis ball’s falls faster.
- Part C: tennis ball 55%, 55%, 57%, 53%; rubber bouncy ball 80%, 80%, 80%, 80%. Each ball keeps about the same share every bounce: the tennis ball about 55%, the rubber bouncy ball about 80%.
- Part D: 1. Gravitational potential → kinetic → elastic (the squashed ball) → kinetic → gravitational potential, with heat and sound branching off at the landing. 2. It became heat in the ball, the floor and the air, and sound; it was transferred, not destroyed. 3. The tennis ball keeps a smaller share each bounce: more of its energy becomes heat as its felt and rubber squash, so its bounces die away faster.
- Bigger: 11 bounces (100 × 0.8 multiplied 11 times is about 8.6 cm).
- Exit tickets: 1. 1.5 ÷ 2 × 100 = 75%. 2. Heat in the ball and the floor, and sound. 3. False: it was transferred to the floor and the air and changed form; the total is the same.
Where does the energy go?
A. Bounce heights (cm)
| Ball | Drop | 1st | 2nd | 3rd | 4th |
|---|---|---|---|---|---|
| Tennis ball, example class | 100 | 55 | 30 | 17 | 9 |
| Tennis ball, ours | 100 | ||||
| Rubber bouncy ball, example class | 100 | 80 | 64 | 51 | 41 |
| Rubber bouncy ball, ours | 100 |
B. Graph
Plot both balls on the same axes (bounce 0 is the drop), join each ball’s points, and add a key.
C. The share kept each bounce
Share kept (%) = this bounce ÷ the height before it × 100
| Ball (example class) | 1st | 2nd | 3rd | 4th |
|---|---|---|---|---|
| Tennis ball | ||||
| Rubber bouncy ball |
D. Questions
Exit tickets
Cut out one ticket for each student.
1. A ball dropped from 2 m bounces back to 1.5 m. What percentage of its height did it keep?
2. Where did the rest of its energy go?
3. True or false: the ball’s energy was destroyed. Explain.
1. A ball dropped from 2 m bounces back to 1.5 m. What percentage of its height did it keep?
2. Where did the rest of its energy go?
3. True or false: the ball’s energy was destroyed. Explain.
1. A ball dropped from 2 m bounces back to 1.5 m. What percentage of its height did it keep?
2. Where did the rest of its energy go?
3. True or false: the ball’s energy was destroyed. Explain.
1. A ball dropped from 2 m bounces back to 1.5 m. What percentage of its height did it keep?
2. Where did the rest of its energy go?
3. True or false: the ball’s energy was destroyed. Explain.
Swings and roller coasters
On a track with no friction, a marble’s energy is shared between gravitational potential and kinetic, and the total never changes: high on the track it is slow, low on the track it is fast, and it can never climb higher than where it started. A real track has friction and air resistance, which turn a little energy into heat and sound on every metre, so a real marble always stops a little lower. A pendulum does the same. Groups build a marble track from foam pipe insulation and find the highest hill the marble can climb, then match energy bar cards to five points on a track drawn to scale.
We are learning to
- describe the changes between gravitational potential and kinetic energy on a track or a swing,
- use energy bars to show how a fixed amount of energy is shared,
- explain why a marble cannot climb higher than its start.
Success criteria
- I can match the five bar cards to the points on the track and explain each match.
- I can predict whether a marble will get over a hill, and say why a real marble falls short.
You need
- for each group: a 2 m length of foam pipe insulation cut in half along its length (two tracks), masking tape, a marble and a metre ruler,
- a pendulum for the opening: a string about 1.5 m long with a heavy bob, hung from a hook or a door frame,
- the worksheet (next sheet), one per student, and the bar cards (third sheet), one set per pair.
Lesson flow (about 60 minutes)
| 5 min | The pendulum Stand still with your back to a wall, hold the bob against your chin and let it go without pushing. It swings away and comes back, but never quite to your chin. Ask: “Why can it never come back higher than where I let it go?” |
| 10 min | On the board Show the board (see the box). |
| 20 min | Build a hill Groups tape a track with a high start and a hill, and raise the hill until the marble just fails to get over. They try three start heights and record in Part A. Ask: “Has anyone’s marble climbed a hill higher than its start? What would it need?” |
| 15 min | Bar cards Pairs work out the energy at each point of the drawn track in Part B, then match the five bar cards. |
| 10 min | Questions Students answer Part C. |
Running two half-sessions instead? Do the pendulum, the board and the track building in Session A, and the bar cards and Part C in Session B.
Watch for these ideas
- “On a smooth enough track, a marble can climb any hill.” Not higher than its start: that would need more energy than it began with.
- “At the top of a hill the marble has no energy.” It has gravitational potential energy, and some kinetic energy if it is still moving.
- “The pendulum slows down because its energy is used up.” Air resistance and the rub at the top turn some of it into heat.
Make it easier, make it bigger
- Easier: match the cards for A, B and E first; they are the clearest.
- Bigger: why must the first hill of a real roller coaster be the highest one on the ride?
Answers and look-fors
- Part A: the highest hill the marble climbs is always a little lower than its start, and no marble climbs higher than its start without a push.
- Part B: A potential 60, kinetic 0, card Q; B potential 0, kinetic 60, card T; C potential 40, kinetic 20, card S; D potential 10, kinetic 50, card P; E potential 50, kinetic 10, card R.
- Part C: 1. At B, the lowest point: all 60 units are kinetic there. 2. No: to reach 70 cm it would need 70 units, and it only has 60. 3. Friction and air resistance turned some energy into heat and sound along the way; it is not destroyed, but it is no longer in the marble. 4. It starts with a fixed amount of energy; some becomes heat on every swing, and it would need a push to gain more.
- Bigger: the train starts with only the energy the lift hill gives it, and loses a little to friction all the way round, so every later hill must be lower.
Swings and roller coasters
A. Build a hill
| Try | Start height (cm) | Highest hill the marble got over (cm) |
|---|---|---|
| 1 | ||
| 2 | ||
| 3 |
B. The drawn track
The marble starts still at A. Pretend there is no friction, and count 1 unit of energy for every centimetre of height at A.
| Point | Height (cm) | Potential (units) | Kinetic (units) | Bar card |
|---|---|---|---|---|
| A | ||||
| B | ||||
| C | ||||
| D | ||||
| E |
C. Questions
Which point is it?
Cut out the cards. Each card shows the marble’s energy at one point on the drawn track, with no friction. Every line on the bars is 10 units. Match each card to its point.
Teacher note: the cards are printed in a different order from the points; the matches are on the plan.
Stretch and release
Stretching or squashing a springy object stores elastic potential energy, and letting it go turns that store into kinetic energy. The further the stretch, the more energy is stored, and the store grows faster than the stretch: for a spring, twice the stretch stores four times the energy. A rubber band behaves much the same until it is stretched near its limit. Groups launch a toy car with a rubber band looped round two chair legs, pull it back by four different stretches, and measure how far it rolls. The distance is a measure of the energy, and the graph shows the curve.
We are learning to
- describe the energy changes when a stretched band is released,
- investigate how the stretch affects the energy stored,
- recognise a pattern where doubling one quantity multiplies another by four.
Success criteria
- I can graph distance against stretch and describe the shape of the curve.
- I can use the results to show that twice the stretch gives about four times the distance.
You need
- for each group: a wide rubber band, two chair legs (or two pegs clamped to a bench), a toy car, a ruler taped to the floor, a tape measure and eye protection,
- the worksheet (next sheet), one per student, and the exit tickets (third sheet).
Safety: eye protection on; launch only along the floor, never towards people; stretch no more than the 8 cm in the table, since an overstretched band can snap.
Lesson flow (about 60 minutes)
| 5 min | A stretched band Stretch a rubber band between your fingers and hold it. Ask: “This band now stores energy. Where did that energy come from?” |
| 10 min | On the board Show the board (see the box). Add elastic potential energy and chemical potential energy to the word wall. |
| 25 min | Launch Groups set up the launcher, measure each stretch from where the band is just straight, launch three times at each stretch and record in Part A. Ask: “Why do we measure the stretch from where the band is just straight, not from where it hangs loose?” |
| 20 min | The pattern Students draw the graph in Part B, work through Part C and answer Part D. |
Running two half-sessions instead? Do the opening, the board and the launches in Session A, and the graph, the pattern and the questions in Session B.
Watch for these ideas
- “Twice the stretch stores twice the energy.” For a spring it stores four times as much, and the results show it.
- “The band makes energy when you let go.” The energy came from the person who stretched it: chemical energy in their muscles.
- “The further the stretch the better, with no limit.” An overstretched band stops springing back, or snaps; every elastic material has a limit.
Make it easier, make it bigger
- Easier: test 2 cm and 4 cm only, and compare the two distances.
- Bigger: use the pattern to predict the distance for a 10 cm stretch. Why might a real band fall short of the prediction?
Answers and look-fors
- Part B: a curve that gets steeper as the stretch grows (it bends upwards), not a straight line.
- Part C: distance ÷ (stretch × stretch) = 3 at 2 cm, 2.9 at 4 cm, 2.9 at 6 cm, 3 at 8 cm: about the same each time, so the distance grows with the square of the stretch. From 2 to 4 cm the distance goes up 3.9 times; from 4 to 8 cm, 4 times.
- Part D: 1. The numbers are about the same, so the distance, and the energy stored, grow with the square of the stretch: twice the stretch, four times the energy. 2. Chemical (in the muscles) → elastic (in the band) → kinetic (the car) → heat and sound as friction between the wheels, the axles and the floor slows the car. 3. A loose band stores nothing until it is straight; only the stretch beyond that point stores energy.
- Bigger: about 300 cm (3 × 10 × 10). A real band may be near its limit and store less than the pattern says, and a longer roll meets more bumps and friction.
- Exit tickets: 1. About 108 cm: twice the stretch, four times the distance. 2. Elastic (the stretched mat and springs) → kinetic → gravitational potential as you rise. 3. Chemical energy in the muscles of whoever stretched it.
Stretch and release
A. Launches (distance the car rolls, in cm)
| Stretch (cm) | Example class mean | Ours: 1 | 2 | 3 | Our mean |
|---|---|---|---|---|---|
| 2 | 12 | ||||
| 4 | 47 | ||||
| 6 | 106 | ||||
| 8 | 189 |
B. Graph
Plot the example class means (or your own) and draw a smooth curve through the points, starting at 0.
C. The pattern
| Stretch (cm) | 2 | 4 | 6 | 8 |
|---|---|---|---|---|
| Stretch × stretch | ||||
| Distance ÷ (stretch × stretch) |
D. Questions
Exit tickets
Cut out one ticket for each student.
1. A band pulled back 3 cm sends a car 27 cm. Predict the distance for a 6 cm stretch.
2. Name the energy changes when a trampoline throws you up into the air.
3. Where did the energy to stretch the band come from?
1. A band pulled back 3 cm sends a car 27 cm. Predict the distance for a 6 cm stretch.
2. Name the energy changes when a trampoline throws you up into the air.
3. Where did the energy to stretch the band come from?
1. A band pulled back 3 cm sends a car 27 cm. Predict the distance for a 6 cm stretch.
2. Name the energy changes when a trampoline throws you up into the air.
3. Where did the energy to stretch the band come from?
1. A band pulled back 3 cm sends a car 27 cm. Predict the distance for a 6 cm stretch.
2. Name the energy changes when a trampoline throws you up into the air.
3. Where did the energy to stretch the band come from?
Energy passing through systems
A system is the set of parts we choose to study together, such as a torch or a cyclist and a bike; the system boundary is the line we draw around it. Energy transfer means energy moving from one object or place to another; energy transformation means energy changing from one form into another. Most devices do both. An energy flow diagram shows each form as a box, with arrows for the changes: the main output goes straight on, and the other outputs, usually heat and sound, branch off. Groups visit six energy stations, record the energy in and out at each and one transfer, then draw flow diagrams for two systems.
We are learning to
- tell an energy transfer from an energy transformation,
- draw an energy flow diagram for a device,
- choose a system and draw its boundary.
Success criteria
- At each station I can name the energy in, the energy out and one transfer.
- I can draw a flow diagram with the main output and the other outputs branching off.
You need
- six stations, each with its station card (third sheet): a torch; a wind-up toy; nothing extra for the hands station; a ball and a metal tray; a small solar fan (or a solar cell and a motor) and a desk lamp; a battery fan,
- the worksheet (next sheet), one per student.
Safety: keep the desk lamp’s cord tidy and the lamp away from the edge of the bench; the ball is dropped, not thrown.
Lesson flow (about 60 minutes)
| 5 min | Where does it come from? Point to a light in the room. Ask: “Where does the energy for this light come from, and where does it go after it leaves the globe?” |
| 10 min | On the board Show the board (see the box). Add system and energy flow diagram to the word wall. |
| 30 min | Six stations Groups spend about four minutes at each station, follow the card and record in Part A. Move them on together. Ask: “At this station, where does energy pass from one object to another?” |
| 15 min | Flow diagrams Model the torch flow diagram on the board with its boundary; students draw the cyclist in Part B and answer Part C. |
Running two half-sessions instead? Do the opening, the board and three stations in Session A, and three stations and the flow diagrams in Session B.
Watch for these ideas
- “Transfer and transformation mean the same thing.” Transfer is from object to object; transformation is from form to form.
- “A device makes energy.” A device only changes the form of the energy it is given, or passes it on.
- “Wasted energy is destroyed.” It spreads into the surroundings as heat and sound, where it is hard to use again.
Make it easier, make it bigger
- Easier: visit stations 1 to 3 only, and give the energy-in words for each.
- Bigger: draw a flow diagram for a hydro-electric power station, from water held behind the dam to a light globe in a home.
Answers and look-fors
- Part A: 1 torch: chemical (battery) → electrical → light, also heat; transfer: electrical energy moves along the wires from the battery to the globe. 2 wind-up toy: elastic (spring) → kinetic, also sound and heat; transfer: your hand passes energy to the spring as you wind it. 3 hands: kinetic → thermal, also sound; transfer: energy moves from your moving hands into the skin as heat. 4 dropped ball: gravitational → kinetic → sound, also heat in the ball and the tray; transfer: the ball passes energy to the tray when it lands. 5 solar fan: light → electrical → kinetic, also heat and sound; transfer: light carries energy from the lamp or the Sun to the panel. 6 battery fan: chemical (battery) → electrical → kinetic, also sound and heat; transfer: the moving blades pass energy to the air.
- Part B, the torch: chemical (battery) → electrical → light, with heat branching off at the globe; the boundary goes round the battery, the switch, the wires and the globe. The cyclist: chemical (food) → kinetic, and gravitational potential as the bike climbs, with heat (and a little sound) branching off; the boundary goes round the rider and the bike.
- Part C: 1. For example, a fan, a drill, a blender or an electric car: electrical → kinetic. 2. When the ball lands, it passes energy to the tray, which vibrates and makes the sound. 3. Both: electrical energy is transferred along the cable to the phone, and transformed into chemical energy in the battery.
- Bigger: gravitational (water held behind the dam) → kinetic (falling water spins the turbine) → electrical (in the generator) → transferred along power lines → light and heat in the globe, with heat and sound branching off at every step.
Energy passing through systems
A. Six stations
| Station | Energy in | Main energy out | Other energy out | One transfer (from what to what) |
|---|---|---|---|---|
| 1. Torch | ||||
| 2. Wind-up toy | ||||
| 3. Hands | ||||
| 4. Dropped ball | ||||
| 5. Solar fan | ||||
| 6. Battery fan |
B. Two flow diagrams
Draw each flow diagram with the main output straight on and the other outputs branching off. Then draw the system boundary.
C. Questions
Energy stations
Cut out the cards and put one at each station with its equipment.
Switch the torch on and off.
Leave it on for a minute, then feel the front of the torch. Is it warm?
What form is the energy in at the start? What forms come out? Where does energy pass from one object to another?
Wind the toy up, then let it go on the bench.
Listen as it runs, and watch when it stops.
What form is the energy in at the start? What forms come out? Where does energy pass from one object to another?
Rub your palms together quickly for ten seconds.
Feel your palms, then rub more slowly and compare.
What form is the energy in at the start? What forms come out? Where does energy pass from one object to another?
Hold a ball 50 cm above a tray and let it go.
Listen as it lands, and watch how high it bounces.
What form is the energy in at the start? What forms come out? Where does energy pass from one object to another?
Hold the solar panel under a lamp or in the sun, then shade it.
What happens to the fan when the panel is shaded?
What form is the energy in at the start? What forms come out? Where does energy pass from one object to another?
Switch the fan on and feel the air.
After a minute, touch the motor casing.
What form is the energy in at the start? What forms come out? Where does energy pass from one object to another?
Useful and wasted energy
Every transformation sends some energy into forms we did not want, usually heat and sound. We call it wasted energy, but it is not destroyed: it spreads into the surroundings, where it is hard to use again. A Sankey diagram draws each flow of energy as a band whose width shows the amount, so the widths of the outputs always add up to the input. Efficiency compares the useful output with the input: efficiency (%) = useful energy out ÷ energy in × 100. Students compare five devices, read a worked Sankey diagram, and draw two of their own to scale.
We are learning to
- identify the useful and the wasted energy from a device,
- draw a Sankey diagram to scale,
- calculate efficiency and compare devices.
Success criteria
- I can draw a Sankey diagram whose output widths add up to its input.
- I can calculate the efficiency of a device and say which device wastes the most.
You need
- the worksheet (next sheet) and the Sankey grid sheet (third sheet), one each per student; rulers and two coloured pencils,
- if you have them: two desk lamps of about the same brightness, one with a filament or halogen globe and one with an LED globe.
Safety: filament and halogen globes get very hot. Students hold a hand about 10 cm from each globe; nobody touches a globe.
Lesson flow (about 60 minutes)
| 5 min | Two lamps Switch on both lamps (or ask why a laptop or a phone charger gets warm). Ask: “Both lamps give about the same light. Why does one feel so much hotter?” |
| 10 min | On the board Show the board (see the box). Add useful energy, wasted energy, efficiency and Sankey diagram to the word wall. |
| 15 min | Reading a Sankey diagram Talk through the worked diagram for the filament globe on the worksheet. Ask: “How can you tell from the picture alone that most of the energy is wasted?” |
| 30 min | Five devices Students complete Part A, draw the two Sankey diagrams on the grid sheet, and answer Part B. |
Running two half-sessions instead? Do the lamps, the board, the worked diagram and Part A in Session A, and the grid sheet and Part B in Session B.
Watch for these ideas
- “Wasted energy disappears.” It spreads into the surroundings, warming the room a little.
- “An efficient device uses less energy.” It wastes a smaller share of what it takes in, so it needs less to do the same job.
- “A device could be more than 100% efficient.” The useful output can never be more than the input.
Make it easier, make it bigger
- Easier: do Part A for the two globes first, and draw only the LED globe on the grid.
- Bigger: an LED globe gives the same light as a filament globe that takes in 100 J each second. About how much energy does the LED globe need each second?
Answers and look-fors
- Part A: filament light globe: wasted 95 J, efficiency 5%; led light globe: wasted 70 J, efficiency 30%; electric kettle: wasted 10 J, efficiency 90%; car engine: wasted 75 J, efficiency 25%; human muscles: wasted 75 J, efficiency 25%. Most efficient: the electric kettle; least: the filament light globe.
- Grid sheet: the LED light globe has a band of 10 squares splitting into 3 squares of light and 7 of heat; the car engine splits into 2.5 squares of kinetic energy and 7.5 of heat and sound. Look for widths that add up, and the wasted band turning away.
- Part B: 1. Three quarters of the energy from the petrol becomes heat, much of it in the engine. 2. For the same light an LED globe takes in far less energy, so it costs less to run and heats the room less. 3. The output bands together are exactly as wide as the input band, so no energy is made or lost.
- Bigger: the filament globe gives 5 J of light each second. The LED globe turns 30% into light, so it needs 5 ÷ 0.3 ≈ 16.7 J each second, about a sixth as much.
- Grid sheet, last question: 140 J wasted; efficiency 60 ÷ 200 × 100 = 30%.
Useful and wasted energy
A. Five devices, each given 100 J
Efficiency (%) = useful energy out ÷ energy in × 100. The values are typical; real devices vary.
| Device | Energy in | Useful energy out | Wasted energy out | Efficiency (%) |
|---|---|---|---|---|
| Filament light globe | 100 J electrical | 5 J light | ____ J heat | |
| LED light globe | 100 J electrical | 30 J light | ____ J heat | |
| Electric kettle | 100 J electrical | 90 J heating the water | ____ J heating the kettle and the air | |
| Car engine | 100 J chemical (petrol) | 25 J kinetic | ____ J heat and sound | |
| Human muscles | 100 J chemical (food) | 25 J kinetic | ____ J heat |
A worked Sankey diagram: the filament globe
The width of each band shows the amount of energy. The useful output goes straight on; the wasted output turns away.
B. Questions
Draw them to scale
One square on the grid stands for 10 J, so each input band is 10 squares wide. Draw the LED light globe on the left half and the car engine on the right half. Label every band with its form and its energy in joules.
A chain-reaction machine
Engineers chain transformations together on purpose. A chain-reaction machine passes energy from one part to the next, and each step sets off the one after it. A standing domino, a marble at the top of a ramp and a stretched rubber band are all stores of energy put there by the builder; the start action only releases the first one, and each part then releases the next. Every step also turns a little energy into heat and sound. Teams design and build a table-top machine with at least four energy transformations that ends by dropping a marble into a cup, then test it, find where it fails and improve it.
We are learning to
- design a system that transfers and transforms energy in a planned order,
- draw an energy flow diagram for a system we built,
- test a design, find where it fails, and improve it.
Success criteria
- Our machine has at least four energy transformations and runs from one start action to the finish.
- I can point to each transformation in our machine and the energy wasted at it.
You need
- for each team of three or four: dominoes or wooden blocks, marbles, a toy car, books, rulers, cardboard tubes and strips, string, paper cups, rubber bands and masking tape; a small bell if you have one,
- the design brief (next sheet) and the test log (third sheet), one each per team.
Before the lesson, build a short chain yourself (a ruler ramp, a few dominoes and a cup) to run in the opening.
Lesson flow (about 60 minutes)
| 5 min | A short chain Run your chain: a marble rolls down the ramp, topples the dominoes, and the last one pushes a marble into the cup. Ask: “The first marble was tiny, yet it knocked down every domino. Where did all that energy come from?” |
| 10 min | On the board Show the board (see the box), then read the design brief together. |
| 10 min | Plan Teams sketch their machine and fill in the energy at each step on the brief before they touch any materials. |
| 25 min | Build and test Teams build in stages, testing each stage on its own, then the whole machine. They record every test in the log. Ask: “Which step fails most often? What could make that step more reliable?” |
| 10 min | Show and reflect Two or three teams run their machines for the class and name each transformation as it happens; all teams answer the reflection questions. |
Running two half-sessions instead? Do the opening, the board and the plan in Session A, and the build, the tests and the showing in Session B.
Watch for these ideas
- “The more steps, the better.” Every step wastes some energy, so a long chain only works if energy has been stored along the way.
- “The falling dominoes make energy.” Each domino releases the gravitational potential energy it got when someone stood it up; the push only starts the chain.
- “When the machine stops, the energy has gone.” It has spread out into the room as heat and sound.
Make it easier, make it bigger
- Easier: aim for three transformations, starting from a ramp, a row of dominoes and a cup.
- Bigger: add a step that lifts something, such as a falling weight on a string over a pencil that raises a cup. Which energy store grows?
Answers and look-fors
- The plan: each step names the energy before and after, for example gravitational (marble at the top) → kinetic (rolling) → kinetic (domino toppling, releasing its own gravitational energy) → sound (the bell), with heat and sound wasted at each collision.
- The test log: changes are made one at a time, and each is tested again, the way a fair test changes one variable.
- Reflection: 1. Usually a collision or a sliding step, where much of the energy becomes heat and sound. 2. In everything the team set up: raised marbles, standing dominoes, stretched bands; the energy came from the builders’ muscles. 3. For example, guide rails, a steeper ramp, or dominoes spaced more closely.
- Bigger: the falling weight’s gravitational energy becomes the cup’s gravitational energy as it rises, less what friction wastes at the pencil.
A chain-reaction machine
The brief
- At least four energy transformations, one after another.
- One start action only: a single push, or letting go of one thing.
- It finishes by dropping a marble into a paper cup.
- It fits on one desk.
- No flames, no water, no mousetraps, and nothing launched at anyone.
Our sketch
The energy at each step
| Step | What happens | Energy changes from … to … | Energy wasted |
|---|---|---|---|
| 1 | |||
| 2 | |||
| 3 | |||
| 4 | |||
| 5 | |||
| 6 |
Test, fix, test again
| Test | What happened | Where it failed | The one change we made |
|---|---|---|---|
| 1 | |||
| 2 | |||
| 3 | |||
| 4 | |||
| 5 | |||
| 6 |
Reflection
Show what we know
The last lesson brings the term together on a skate park half-pipe. Students work out the skater’s gravitational potential energy at the top, share it between potential and kinetic energy at three points with no friction, then look at the real ride, where the skater stops lower on the far side, and account for the missing energy with a Sankey diagram. Then each student sits the final check on their own, and the class finishes with the unit quiz on the board.
We are learning to
- calculate and track energy through a system,
- explain where energy goes, using transfers, transformations and conservation,
- show what we know about energy on our own.
Success criteria
- I can account for all of the skater’s energy, including the part that became heat and sound.
- I can back each answer on the final check with a form of energy, a calculation or a reason.
You need
- the half-pipe task (next sheet) and the final check (third sheet), one each per student, and a calculator,
- the interactive unit open for the closing quiz.
Lesson flow (about 60 minutes)
| 5 min | Brief Look at the half-pipe together, without answering. Ask: “The skater starts still at A. Where on the ride will the skater be fastest?” |
| 20 min | The half-pipe Students work alone on the task. |
| 10 min | Check with a partner Partners swap tasks and check the numbers in Parts A and B. Ask: “Do your partner’s potential and kinetic energies add up to the same total at every point?” |
| 15 min | Final check Hand out the final check. Students work alone; read each item aloud once if needed, and help with reading, not answers. |
| 10 min | The class quiz Run the unit quiz on the board as a whole-class game (see the box). Ask: “One last time: if energy is never destroyed, why do we still talk about wasting it?” |
Running two half-sessions instead? Do the task and the partner check in Session A, and the final check and the class quiz in Session B.
Watch for these ideas
- Using the height in centimetres, or forgetting the 9.8: the formula needs kilograms and metres.
- Saying the missing energy at D was used up or destroyed; it became heat and sound in the board, the wheels and the air.
- Bars at C that do not add up to the same total as at A; with no friction the total is the same everywhere.
Make it easier, make it bigger
- Easier: give the energy at A, and ask for B and C only.
- Bigger: with no friction, how fast is the skater going at B? (Kinetic energy = ½ × mass × speed × speed.)
Answers and marking guide
- Task A: A potential 1470 J, kinetic 0 J; B potential 0 J, kinetic 1470 J; C potential 735 J, kinetic 735 J; the total is 1470 J at every point (at A: 50 × 9.8 × 3 = 1470 J). Bars: A all potential, B all kinetic, C half and half.
- Task B: at D, 50 × 9.8 × 2.4 = 1176 J of potential energy and no kinetic energy; 1470 − 1176 = 294 J became heat and sound, which is 20% of the start.
- Task C: an input band of 1470 J splitting into 1176 J of gravitational potential energy (straight on) and 294 J of heat and sound (turning away), with the widths in proportion.
- Task D: friction and air resistance turn some energy into heat and sound on every ride, so to reach A again the skater must add energy by pushing or pumping, using chemical energy from food in the muscles.
- Check: 1. elastic potential energy. 2. Its particles are moving quickly; thermal energy is the kinetic energy of particles. 3. decreases. 4. 2 × 9.8 × 1.5 = 29.4 J.
- Check: 5. 20%. 6. Elastic (wound spring) → kinetic (moving car), with sound and heat branching off. 7. Each landing turns some kinetic energy into heat and sound in the ball, the floor and the air; it is transferred and transformed, not destroyed. 8. Kinetic energy grows with the square of the speed, so at twice the speed the car carries four times the energy, takes about four times as far to stop, and does far more damage.
- Bigger: ½ × 50 × speed × speed = 1470, so speed × speed = 58.8 and the speed is about 7.7 m/s.
- Scoring: 1 mark each for 1, 3 and 5; 2 marks each for 2, 4, 6, 7 and 8. The rubric near the front of the pack turns the task and the check into a level.
The half-pipe
Kai, a 50 kg skater, starts still at A and rolls down into the half-pipe. Use gravitational potential energy (J) = mass (kg) × 9.8 × height (m).
A. With no friction
| Point | Height (m) | Potential energy (J) | Kinetic energy (J) | Total (J) |
|---|---|---|---|---|
| A | 3 | |||
| B | 0 | |||
| C | 1.5 |
Shade the bars for each point. Each line is a quarter of the total.
B. The real ride
C. A Sankey diagram for the ride from A to D
D. Explain
Show what we know
Show what you know about energy. Read each item, then circle or write.
Teacher note: the marking guide is on this lesson’s plan; the rubric near the front of the pack turns the score into a level.