Question

A 6 Kg cart on a level surface is pulled at a constant velocity of 2 m/sec by a constant force of 10 N. What is the acceleration? What is the friction force opposing the motion?

Answer 1

As the car is pulled at a constant velocity, the acceleration and vector sum of the forces acting on the car equals to zero.
Thus a = 0; F - F_frict = 0; F_frict = 10 N.