A box weighing 6kg is pushed to the left at a constant speed

Question

The coefficient of friction is 0.78. What is the force with which the hand pushes the box?

Answer 1

Being pushed at constant speed means no acceleration; ΣF_x = f + F = 0 where friction force f = μ_kF_n is acting to the right and applied force F to the left. The normal force F_n is the weight mg. That makes the applied force F = - (0.78) (6 * 9.8) = -45.9 N.