Question

A 60.0 kg runner is moving at 6.00 m/s and speeds up to 9.00 m/s. The runner’s change in kinetic energy is 1,350 J.

How much work was done?

–2,430 J
–1,350 J
1,350 J
2,430 J

Answer 1

Work = change in kinetic energy (work–energy theorem). ΔK = 1/2 m (v_f^2 − v_i^2) = 1/2·60(9^2 − 6^2) = 2430 − 1080 = 1350 J.

Answer: 1,350 J