Question

A 105 kg crate initially at rest on a horizontal floor requires a 705 N horizontal force

to set it in motion. Once the crate is in motion, it requires a 595 N horizontal force
to keep it moving at a constant velocity. Find the coefficient of static friction and the
coefficient of kinetic friction between the floor and the crate.

Answer 1

μs = 0.68

μk = 0.577

Step-by-step explanation:

In order to solve this problem, we must remember that the normal force on a body that rests on a horizontal surface is equal to the weight of a body but in the opposite direction.

`W=N\\N=m*g\\N=105*9.81\\N=1030.05[N]`

The friction force is defined as the product of the coefficient of friction by the normal force.

Now when the body is in motion we have that the coefficient of friction is the dynamic one.

595 = μk*N

μk = 595/1030.05

μk = 0.577

Now to start moving it requires a force of 705 [N].

705 = μs*N

μs = 705/1030.05

μs = 0.68