Practice!

Sample Problem

A sled is pushed with a constant force across a frictionless ice rink. Which of the following free-body diagrams most accurately represents the forces acting on the sled?

Solution

We know that since the sled is not accelerating vertically up or down (it’s not rising or falling through the ice) , the normal force and the weight must be equal. Furthermore, we can see from the diagram that the applied force is directed to the right.