Forces
Spring balance
Measure a spring constant from the extension caused by a known weight.
k = F / x
Apparatus
- Mystery spring
- Slotted masses
- Metre rule
- g = 10 N/kg
Method
- Choose spring A, B, or C. You are not told k.
- Hang a mass. The weight is the force: F = mg, with the mass in kilograms.
- Read the extension in centimetres, then convert to metres.
- Calculate k = F / x and check it. Try a second mass: k should come out the same.
Do not overload a real spring past its elastic limit. It will not return.
Extension
8cm
Force
2N
Spring
A
Mass
200g
Spring
Extension proportional to force, so k is the same at every load.
Back to the Forces lesson