Question

A man is sliding a 50 kg box across the floor with a normal force of 500 N. The floor is very rough, and the friction force is 450 N. What is the net force?

Answer 1

The gravity is balanced by the surface reaction force, so, only the friction and traction forces are acting. Since the friction force is directed opposite the traction force, the net force is 500N - 450N = 50N and it's directed across the floor the same as the traction force.