# Kinetic friction between the box and the ramp

Coefficient of kinetic friction so im working on the force of friction and overcoming friction
i know that the coeffcient of friction is equal to the kinetic force over the normal force and i can get these when hte system is on a horisantal surface
But i dont understand how to get them with an incline

Problem: a box slides down a 30 degree ramp with an acceleration of 1.2 m/s squared. Determine the coefficient of kinetic friction between the box and the ramp.

im not sure i even know where to start, well i have a free body diagram

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ok so i got that the force perpendicular (x) - (subtract) the force of friction = mass*acceleration of x
but the question does not give you a mass!
how do i determine the normal force if i don't have a mass?

What is the acceleration down the ramp with no friction?

Dorothy

um it says 1.2 m/s squared

That is WITH friction. What is it without friction?

how do i find that out? i dont know what the force of friction is in this problem

allblonde said:
how do i find that out? i dont know what the force of friction is in this problem
Well, let me put it to you this way. You have a freebody diagram. What are your force equations? Let's take a look at those.