It is given that, Polly is pushing a box across the floor with a force of 30 N. The force of gravity is –8 N, and the normal force is 8 N.
We know that the frictional force is an opposing force. It always opposes the motion. It acts in the direction opposite to the direction of motion.
In this case, the box is pulled with a force of 30 N. So, the force of friction so that the box does not move will be 30 N but it acts in opposite direction.
