Forces and elasticity

The idea

Stretching, bending or compressing an object needs more than one force. Elastic deformation means the object returns to its original shape when the forces are removed; inelastic deformation means it does not. For a spring, the extension is directly proportional to the force applied, F = ke, up to the limit of proportionality. The spring constant k is in N/m. If the spring is not inelastically deformed, the work done stretching it is stored as elastic potential energy.

1. Find the extension: new length − original length.
2. Use F = ke with e in metres.
3. Check whether the limit of proportionality has been passed.

Watch out Extension is the increase in length, not the total length.