# Homework Help: What is the speed of the crate when it reaches the bottom?

1. Feb 12, 2010

### physx_420

1. The problem statement, all variables and given/known data
A 20.0-kg crate slides down an inclined plane that is 3.00-m high and 20.0-m long. If friction is negligible, what is the speed of the crate when it reaches the bottom of the plane?

2. Relevant equations
W= F*D
K= 1/2 m*(v^2)

3. The attempt at a solution
They don't give me an angle so I'm not sure how I'm supposed to go about solving for the force parallel to the inclined plane. Once I have that I'll be able to finish out the problem. Help please!
(The answer turns out to be 7.67 m/s; I just need to know how to get there)

2. Feb 12, 2010

### N-Gin

Just use conservation of energy. You have gravitational potential energy in the beginning. Don't bother with the work $$W=FD$$.

3. Feb 12, 2010

### physx_420

Ahhh, ok I see. Thanks alot N-gin!

4. Oct 18, 2010

### venkatg

The 20 M long is not needed for this problem because the friction is assumed to be zero. No energy is lost in friction and so M*g*H = (1/2)*M*V^2

So V = sqrt(2*g*H)

So the velocity is independent of the Mass!!!

If you had friction, then still mass is irrelevant.