# Particle sliding on a track (cons. of energy problem)

1. Oct 15, 2008

### musicfairy

A particle can slide along a track with elevated ends and a flat central part, as shown in Figure 8-53. The flat part has length L = 40 cm. The curved portions of the track are frictionless, but for the flat part the coefficient of kinetic friction is µk = 0.32. The particle is released from rest at point A, which is a height h = L/2. How far from the left edge of the flat does the particle finally stop?

I set this equation:

mgh = μmgd

d = h/μ

d = 20/.32

d = 62.5 cm

Because the answer > L, I subtracted 40 cm from it and got 22.5 cm as the answer (I'm supposed to give it in cm). But it won't accept my answer. What did I do wrong?

2. Oct 15, 2008

### Stovebolt

You did all the math right to determine distance - the particle will move 62.5 cm on the flat surface before coming to a stop. Now think about the direction it is traveling and where that is in relation to the left edge of the flat surface.

3. Oct 15, 2008

### musicfairy

Oh, I see.

Thanks a lot for saving me from losing a point. :)