A girl is sitting in a sled sliding horizontally along some snow (there is friction present).

The normal force supporting the girl and sled is 636 N.

If the coefficient of static friction is 0.38, and the coefficient of kinetic friction between snow and sled is 0.25, what is the force of friction exerted on the sled?

Ff = 159 [N]

Explanation:

Since in the problem give us two values of friction coefficient one static and the other dynamic, it is important to keep in mind that in order to solve this problem we must know the conditions in which the sled is located. We can read that the sled is in motion, in this way we use the dynamic coefficient of friction.

The friction force is calculated as the product of normal force, by the appropriate coefficient of friction value.

Ff = N * μ

Ff = 636 * 0.25

Ff = 159 [N]