Conservation of Energy Problem

[Distance4life]

1. The problem statement, all variables and given/known data

A roller coaster travels on a frictionless track starting at point A, 5.0m off the ground. It then comes down to point B, 0.0m off the ground (it comes down to the ground), then it goes back up to point C, at 8.0m off the ground.

If the roller coaster is traveling at 5.0m/s at point A, what is the speed at point B?

Will it Reach Point C?

And lastly, What speed at point A is required for the roller coaster to reach point C?

2. Relevant equations

K=1/2mV2
U=mgh


3. The attempt at a solution
U1 +K1=K2
U2 +K3=U1 +K1

K=1/2mV2
2K=mV2
2K/25.0m/s=m

Thats all I have, I seem to have trouble getting mass. Any help would be appreciated. Thanks

D4L

[Delphi51]

Energy at A = energy at B

On each side of the equation write in a .1/2mv² if it has KE and an mgh if it has PE. You should be left with only one unknown that you can solve for.