Understanding the Concept

* Constant Speed: When an object moves at a constant speed, it means the net force acting on it is zero.

* Forces in Balance: In this case, the applied force (100 N) is balanced by the frictional force acting in the opposite direction.

Calculation

Since the box is moving at a constant speed, the forces must be balanced. Therefore, the frictional force acting on the box is 100 N in the opposite direction to the applied force.