Spring scale: a spring measures weight
Weights of 0.5, 1 and 2 kg and one unknown hang on identical springs. A spring stretches in proportion to the load, so the ruler reveals the mass.
2D
Age 8+10 min
ElasticityGravity
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Press “Run”. Bodies move by the laws of physics: gravity, friction, elasticity.
What the experiment shows
The heavier the load, the more the spring stretches: twice the weight, twice the stretch. This is Hooke’s law, the idea behind kitchen and luggage scales.
How to run it
- Press “Run”: the weights bob and settle.
- Read the stretch on the ruler for 0.5, 1 and 2 kg.
- Compare the stretch of the “?” spring and work out its mass.
Questions to discuss
- How many times larger is the stretch at 2 kg than at 1 kg?
- What happens if the weight is far too heavy?
The science
A spring’s force is F = k·x. At rest k·x = m·g, so x = m·g/k. Here k = 10 N/m, so every kilogram stretches the spring by 98 cm. Real springs obey Hooke’s law only up to their elastic limit.
Try it at home
Hang a bag from a rubber band and add coins one at a time. Mark the length — it grows by almost the same step per coin.
What to change in the editor
- Make the spring three times stiffer (k = 30).
- Increase the damping so the weight settles faster.