A child pedals a bicycle along a road at a constant speed.

Question

Why does the bicycle keep moving at a constant speed?

A. The net force on the bicycle is zero.

B. The force of her pedaling is stronger than inertia.

c. The force of friction is larger than the force of gravity.

D. The force of her pedaling is stronger than the force of friction.

Answer 1

The correct answer is:

A. The net force on the bicycle is zero.

When a child pedals a bicycle at a constant speed, it means that the forces acting on the bicycle are balanced. The force produced by pedaling is equal to the forces of friction and air resistance opposing the motion. Therefore, the net force is zero, and according to Newton's first law of motion, an object in motion will continue in motion at a constant speed if the net external force acting on it is zero.