Understanding the Concepts

* Newton's First Law: An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

* Friction: A force that opposes motion between two surfaces in contact.

* Net Force: The sum of all forces acting on an object.

Solving the Problem

Since the box is moving at a constant velocity (no acceleration), the net force acting on it must be zero. This means the force applied (13N) must be equal and opposite to the force of friction.

Therefore, the frictional force between the box and the surface is 13N.