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Grade 3 (age 8-9)

grade 3 Measuring Weight

Measuring Weight

Weight is the force with which the Earth pulls on an object. An apple feels heavier than a balloon, and we measure that weight in g (grams) or kg (kilograms). A spring scale stretches more for a heavier object, while a balance scale stays level when both sides weigh the same. Change the weight and the spring stretches; add weights to each side and the heavier side shows.

What is Weight?

🤔 Feel the Weight
①Compare the apple and balloon on the scale and spring on this screen
②You feel the apple is heavier
③Weight = force of gravity pulling objects
④In elementary school we measure that force in g (gram) and kg (kilogram)

Spring Scale

50g
💡 How Spring Scale Works
①Heavier object → spring stretches more
②Length read = weight
③Read at eye level
④Always check the unit (g or kg)

Balance Scale

30g
50g
⚖️ How to Use Balance Scale
①Place object on one side, weights on the other
②Balanced = sum of weights = object weight
③Lighter side goes up
④Heavier side goes down

Summary

Meaning of Weight
Weight = force of Earth pulling object
Units: g (gram), kg (kilogram) — 1kg = 1000g
Spring Scale
Heavier → spring stretches more
Length stretched → read scale → measure weight
Balance Scale
Balanced = both sides equal weight
Use weights to measure object precisely
🎯 Key Points
①Weight is the force of gravity
②Spring scale: stretch length = weight
③Balance scale: compare with weights
④Units: g, kg
⑤Same volume can have different weight

Examples and Unit Test

Example 1
On a spring scale, what happens to the length of the spring as you hang a heavier object?
1
On a spring scale, the heavier the object, the more the spring stretches.
2
So hanging a heavier object makes the spring stretch longer.
▸ The spring stretches more
A spring scale measures weight by how far the spring stretches (heavier = more stretch).
Example 2
On a pan balance, an apple is on the left and a weight on the right, and the left side goes down. Which is heavier?
1
On a pan balance, the heavier side goes down and the lighter side goes up.
2
Since the left side went down, the apple is heavier than the weight.
▸ The left side (the apple) is heavier
On a pan balance the heavier side goes down; if level, both sides weigh the same.
Unit-test style
Which statement about measuring weight is correct?
①Weight is the force with which the Earth pulls an object
②A spring scale stretches more when the object is lighter
③On a pan balance, the lighter side goes down
④The unit of weight is cm
⑤If a pan balance is level, one side is heavier
▸ ① Weight is the force with which the Earth pulls an object
1
Weight is the force with which the Earth pulls an object, and its unit is g or kg.
2
A spring scale stretches more when heavier (②), on a pan balance the heavier side goes down (③), the unit of weight is g or kg (④), and a level balance means both sides weigh the same (⑤).
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