If Dr. Hewitt applies 3N of force to keep the block moving, what is the force of friction?

In the context of this scenario, if Dr. Hewitt is applying 3N of force to keep the block moving at a constant velocity, it indicates that the forces acting on the block are in equilibrium. According to Newton's first law of motion, an object will remain at rest or move in a straight line at constant speed unless acted upon by a net external force.

When the block is moving at a constant velocity, the net force acting on it is zero. This means that the force of friction must be equal in magnitude and opposite in direction to the applied force. Therefore, if Dr. Hewitt applies a force of 3N to maintain motion, the force of friction opposing that motion must also be 3N.

This situation implies that the forces are balanced; hence the correct answer is that the force of friction is equal to 3N, acting in the opposite direction to the applied force. Understanding this relationship is crucial in analyzing motion and forces in physics.