Question

If a body is moving with uniform speed in a particular direction on a perfectly smooth surface, then no force is acting on it. True or false? Explain.

Answer 1

False.

If no external force is applied on the body, then there must be two equal and opposite forces acting on the body. Both these forces add up to zero.

1. Weight of the body, W = mg (In downward direction)
2. Reaction force, N = W (In upward direction)

Because the surface is smooth, there is no frictional force.