ACARA v9 CONTENT DESCRIPTION “use provided scaffolds to plan and conduct investigations to answer questions or test predictions, including identifying the elements of fair tests, and considering the safe use of materials and equipment”
Builds on earlier work where you planned tests that change just one thing. Now you use a ramp and a toy car to plan a fair test about friction: change only the surface, keep the rest the same, measure the rolling distance, and set the ramp up safely.
What makes the ramp test fair?
You want to know which surface lets a toy car roll the farthest: bare wood, carpet, or sandpaper. To be fair, you must use the same car, set the ramp at the same height, and let the car go from the same release point every time. The only thing you change is the surface the car rolls onto. Then if the car rolls farther on one surface, you can be sure the surface caused it, not something else.
Plan the ramp test: change one thing, keep the rest the same
You are testing which surface lets a toy car roll the farthest. Choose the one thing you will change, and keep everything else fair.
One toy car, one ramp, three surfaces to roll onto: bare wood, carpet and sandpaper. You want to find out which surface the car rolls farthest on, so you must keep everything fair except the surface itself.
Variable being tested: The surface the car rolls onto (wood, carpet or sandpaper) (this one we change)
The car you use (use the same toy car every time)
The ramp height (set it the same for every roll)
The release point (let the car go from the same spot)
Not a fair test yet: more than one thing is changing, so you could not tell which change caused the result. Hold every other variable the same.
Setting the ramp up the safe way
Planning a fair test also means thinking about safety. To start each roll the same way you set the ramp at a height and let gravity do the rest. A very steep ramp can send the car flying off the table, and a cluttered floor means the car could hit someone or you could trip chasing it. A sensible ramp height and a clear landing area keep the test safe while still giving every surface a fair chance.
Pick the safe way to set the ramp height
You need a ramp height that starts every roll the same way without being dangerous. Choose how to set it, and see what each choice gives and gives up.
The ramp height decides how much speed gravity gives the car at the bottom. There is more than one way to set it, and some ways are safer than others.
Choose a response to see what is gained and what is given up.
Which actions make the test fair and safe?
A good plan has actions that keep the test fair and actions that keep you safe. Some things you might do, though, have nothing to do with either. Sort each action by whether it really helps make the ramp test fair and safe, or whether it is beside the point.
Sort the actions for the ramp and car test
The plan: roll a toy car down a ramp onto different surfaces to see which lets it roll farthest. Decide which actions help make the test fair and safe, and which do not.
Claim: To test which surface a toy car rolls farthest on, I should plan a fair test and set the ramp up safely.
Use the same toy car for every surface so only the surface changes.
Let the car go from the same release point each time instead of pushing it.
Keep the landing area clear so the car cannot hit anyone or trip you.
Choose your favourite colour of car before you start.
Measure each rolling distance with a tape measure in centimetres so you can compare fairly.
Decide whether each statement is evidence for the claim, or not.
Why this matters
Planning a fair test is the first job a scientist does. When you change just one thing, keep the rest the same, measure carefully and set your equipment up safely, your answer can be trusted. The same careful planning is used by engineers who test tyres, ramps and brakes every day.
Quick self-check
1. You roll a toy car down a ramp onto different surfaces to see which lets it roll the farthest. What is the one thing you should change?
2. To keep the ramp test fair, what should stay the same for every roll?
3. Why should you let the car go from the same release point each time instead of giving it a push?
4. What is the fair way to measure how far the car rolls?
5. When setting up the ramp, the safe thing to do is...