1. Nov 15, 2008

### lonlyincolleg

1. The problem statement, all variables and given/known data
Bike (mass 40kg) traveling down a hill. Speed at the top of the hill is 5.0 m/s. The hill is 10m high and 100m long. Force of friction is 20N, what is the speed at the bottom?

2. Relevant equations
The only formula I've tried is v(final) = Sq. rt. of 2gy(initial). I don't know what y is, where friction plays into this and obviously I'm not getting the answer. Please help!

3. The attempt at a solution
I have converted the units to kg, and m, and drawn a picture. I know that the answer is 11 m/s but there isn't a formula or very similar problem in my book. (The only similar problem doesn't account for friction so I don't really know where to begin.

2. Nov 15, 2008

### asleight

Conservation of mechanical energy:

$$K_i+U_i-\vec{W}=K_f+U_f$$.

3. Nov 15, 2008