If the force of friction acting on a sliding crate is 79 N, how much force must be applied to maintain a constant velocity?

79N

To determine the amount of force needed to maintain a constant velocity for the sliding crate, we need to consider Newton's first law of motion, also known as the law of inertia. According to this law, an object at rest or moving at a constant velocity will continue to do so unless acted upon by an external force.

In this case, the force opposing the motion of the crate is the force of friction, which is given as 79 N. To balance out this force and keep the crate moving at a constant velocity, we need to apply an equal and opposite force.

Therefore, the amount of force needed to maintain a constant velocity is 79 N, in the opposite direction to the force of friction.