Physics GCSE Science Worksheets, Questions and Revision

A 1200 kg car is travelling at 20 m/s. Calculate its kinetic energy, then find the average braking force needed to stop it in a distance of 40 m.

1. Write the kinetic energy equation: kinetic energy = 0.5 x mass x speed squared.
2. Substitute: 0.5 x 1200 x 20 squared = 0.5 x 1200 x 400.
3. Calculate: 0.5 x 1200 = 600, and 600 x 400 = 240 000 J, which is 240 kJ.
4. For the braking force, use the fact that the work done by the brakes equals the kinetic energy transferred: work done = force x distance.
5. Rearrange for force: force = work done / distance = 240 000 / 40.
6. Calculate: 240 000 / 40 = 6000 N. Final answers: kinetic energy 240 000 J, braking force 6000 N.