Question

A bicyclist increases her speed from 4.0 m/s to 6.0 m/s. The combined mass of the bicyclist and the bicycle is 55 kg. How much work did the bicyclist do in increasing her speed?
A. 11 J
B. 28 J
C. 55 J
D. 550 J

Answer 1

Kinetic energy of the horse and rider = 1/2 (mass) (speed)²

At 4.0 m/s :  KE = 1/2 (55kg) (4 m/s)²  =  440 joules

At 6.0 m/s :  KE = 1/2 (55kg) (6 m/s)²  =  990 joules

She increased the kinetic energy of herself and her vehicle by 550 joules,
so she must have put at least that much work into it.