Question

Polly is pushing a box to the right across the floor with a force of 30 N. The force of gravity is 8 N, and the normal force is 8 N. Which value could describe the force of friction if Polly could not move the box?




Polly is pushing a box to the right across the floor with a force of 30 N. The force of gravity is 8 N, and the normal force is 8 N. Which value could describe the force of friction if Polly could not move the box?

Answer 1

If the box does not move, net horizontal force must be zero, so the frictional force must exactly balance Polly's 30 N push. Thus the friction is 30 N directed to the left (or −30 N if right is taken as positive).