Example: A wooden crate with mass 100kg is at rest on a stone floor. You know that the coefficients of kinetic and static friction are: μs=0.5 and μk=0.4. A) What is the minimum horizontal force F need to just get the crate moving?

Answer

Any force greater 490N

Explanation

The force required just to make an object slide over a rough horizontal surface is any force greater that the static friction which given by;

Given;

Hence;

F = 0.5 x 100 x 9.8

F = 490N.

We will only need the coefficient of kinetic friction if we were asked to find the force required to keep the object moving uniformly. Usually, the force needed to keep an object moving uniformly over a rough surface is lesser that which is needed to start its motion.

In this problem, we were only asked to find the minimum force required to make the object move which we have done.

8 meters above the spring

since you're a real machine, your ama is always less than your ima, because you can never totally eliminate friction.