1. The problem statement, all variables and given/known data A cart slides down an inclined ramp at is 1.44m long. The height of the ramp is .10m. The angle of incline of the ramp is not given. The work done by the friction is -.06. I need to find the friction force. 2. Relevant equations Work done by the friction = Friction force * d cos theta. 3. The attempt at a solution When looking through my books, I found what appears to be two contradictory ways of determining theta - 1) by using sin (sin theta = .10/1.44) so the angle of incline is 4 or 2) by using 180 for theta because the friction force is acting in the opposite direction. Can anyone point me in the right direction? Thanks for your help.