Question

How much work should be done on a bicycle of mass 20 kg to increase its speed from 2 m/s to 5 m/s ? And can we solve this question with work energy theorm?and the right answer is 210 J?i have solved this by work energy theorm but my answer is coming 90 J ? Please help!

Answer 1

final velocity = 5 m/s
initial velocity = 2 m/s

mass= 20 kg

final kinetic energy = (1/2)*mass* (final velocity)^2
final KE = 0.5*20*5^2 = 10*25 = 250 J


initial KE = (1/2)* mass* (initial velocity)^2
initial KE = 0.5*20*2^2 = 10*4 = 40 J

according to work energy theorem
work done = change in kinetic energy = Final KE - initial KE
work done = 250 J -40 J
work done = 210 J


answer is 210 J


thanks for asking.