Question

Guys help me to answer this question of physics class 9 chapterforce and law of motion

Answer 1

Answer:

There is indeed an external force acting on the above case,it is the frictional force which acts as the external force on the wheels, against the motion of the bicycle and to some extend air resistance also acts against the motion of the bicycle. Therefore the bicycle stops after some time if we stop pedaling.

And so we can say that Newton's law is not disturbed in the above case.