Question

Brian is walking through the school cafeteria but does not realize that the person in front of him has just spilled his glass of chocolate milk. As Brian, who weighs 420 N, steps in the milk, the coefficient of sliding friction between Brian and the floor is suddenly reduced to 0.040. What is the force of sliding friction between Brian and the slippery floor?

Answer 1

In order to find the force of sliding friction, you need to know the normal force, or the force the ground exerts upward on Brian. On a horizontal surface this normal force is equivalent to the object’s weight, which in this case is 420 N.