# Homework Help: Finding force of friction

Tags:
1. Mar 9, 2017

### Claire

1. The problem statement, all variables and given/known data
Ok so there was a question on a physics quiz I did that I have no idea how to answer. There was a roller coaster going down a hill with an initial velocity of 1.67m/s. The hill is 60m long and had an angle of 40 degrees. There is a coefficient of friction of 0.100 with the roller coaster. We had to find the final velocity

2. Relevant equations
Ff=uFn
F=ma
d=vot + 1/2at2

3. The attempt at a solution
I honestly had no idea what to do for this question. I assume it had something to do with the x and y components of velocity, but I feel like you need mass or acceleration to answer this question and I don't know how to relate velocity to friction.

Last edited by a moderator: Mar 9, 2017
2. Mar 9, 2017

### TomHart

Can you post your free body diagram please. By the way, welcome to Physics Forums.

3. Mar 9, 2017

4. Mar 9, 2017

### haruspex

Not really.
When a problem like this does not provide mass, either as a definite value or as an unknown allowed in the answer, it is a fair bet that it does not matter what the mass is. Just create an unknown, m, for it and expect it to cancel out later.
It can be done that way, but you do not need to find the acceleration.
Find the forces, then think about work done.

5. Mar 9, 2017

### Claire

Thank you to everyone who offered to help, I figured out the answer!