A moving bicycle comes to rest after sometime if we stop pedalling it. But Newton's first law of motion that a moving body should continue to move for ever, unless some external force acts on it. How do you explain the bicycle case?

Explanation

It we stop panddling a bicycle which is moving at uniform speed, the bicycle does not go on moving forever, it comes to rest after some time. The moving bicycle has been compelled to change its state of uniform motion by the external force of air resistance and friction. If there were no air resistance and no friction to oppose the motion of the bicycle, then according to first law of motion, a moving bicycle would go on moving forever. It would not stop by itself. Therefore, Newton's law is applicable here.