What is their kinetic energy?

Question

A bicycle and rider going 14 m/s approach a hill. Their total mass is 57 kg.

(a) What is their kinetic energy?

(b) If the rider coasts up the hill without pedaling, how high above its starting level will the bicycle be when it finally rolls to a stop?

Answer 1

Kinetic energy is given by (1/2)mv², so it is (1/2)(57 kg)(14 m/s)² = 5586 J. To solve part b, you need to use conservation of energy. The kinetic energy is converted into potential energy. Potential energy is given by mgh, so you have mgh = 5586 J. Therefore, h = 5586 J/(mg) = 10 m.