Physics
posted by Lyna .
A 1.31kg block slides across a rough surface such that it slows down with an acceleration of 1.39 m/s2. What is the coefficient of kinetic friction between the block and the surface?

I think you solve it like this...do you have the answer to verify? I am no genius in physics...
Forces in the x direction = friction = mass x acceleration.
friction forces is found by multiplying the coefficient of friction (u) by the normal force.
so. u x mass x gravity = mass x acceleration
mass cancels so u = 1.39 / 9.8. 
atta go Brenda !