Question

A student, trying to push a box across the floor, slowly increases the force she is applying. She knows the coefficients of static and kinetic friction and has calculated the maximum static friction and kinetic friction When will the box start to slide?

Answer 1

The box will begin to slide when the student applies a force greater than the maximum static friction, calculated using the coefficient of static friction and the normal force.

Step-by-step explanation:

The box will start to slide across the floor when the applied force exceeds the maximum static friction. The static friction force counters the applied force up to a certain threshold, known as the maximum static friction, which can be calculated using the coefficient of static friction and the normal force acting on the object.

In this case, if the box has a mass of 100 kg, and the coefficient of static friction (μs) is 0.45, the maximum static friction force would be fs(max) = μsN = (0.45)(980 N) = 440 N, where 980 N is the normal force resulting from the weight of the box. When the student's applied force is greater than 440 N, the box will begin to slide, transitioning to kinetic friction. Once sliding, the kinetic frictional force is usually less, indicated by a lower coefficient of kinetic friction (μk), meaning less force is required to keep the box moving.