Conservation of Energy of park ride Problem

[Distance4life]

Homework Statement

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?

Homework Equations

K=1/2mV²
U=mgh

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.