Find the coefficient of static friction

[sprinter08]

Homework Statement

A 25kg chair initially at rest on a horizontal floor requires a 165N horizontal force to set it in motion. Once the chair is in motion, a 127N horizontal force keeps it moving at a constant velocity.
a.) Find the coefficient of static friction between the chair and the floor.
b.) Fing the coefficient of kinetic friction between the chair and the floor.

Homework Equations

3. The Attempt at a Solution
I'm not really sure what equation to use the solve the problem. I know that it is probably something really easy as sticking the numbers into a formula, but I don't know the formula, and we don't use a book, so I can't look it up.

 

[shenwei1988]

F=mg
f=mgu
165N is the static friction force
127N is the kinetic friction force
simply put in the number f(s)=F*u

 

[sprinter08]

so would I take 165 and multiply it by the weight of the chair (25 kg) to find static friction and multiply 127 by 25 to find kinetic friction?

 

[shenwei1988]

F=mg=25x9.8
for question 1.) f=Fu ---> 165=25x9.8xu find u , u is the coefficient of static friction between the chair and the floor.

try to do 2 by yourself