# Homework Help: Having trouble finding the horizontal velocity of the object rolling down a ramp

1. Jul 17, 2012

### yokialana

1. The problem statement, all variables and given/known data
I need to find the horizontal velocity of an object on a ramp where the first height is 5.0m and the second height is 3.0m? I also need to find the time it takes to fall from the ramp, and the distance it falls away from the ramp. I am only given the two heights, an initial velocity of 0, and of course I have gravity.

2. Relevant equations
ep=mgh
ek=0.5mv2

3. The attempt at a solution
Not sure where to start even.

2. Jul 17, 2012

### PeterO

I can see your dilemma - I think you need the either the angle of, or the length of, the ramp.

It is fine to use energy considerations to calculate how fast the object [presumably sliding down a frictionless ramp] will be travelling when it leaves the lower end of the ramp, but without an angle you are stumped - other than to derive an answer which includes a variable like θ which could represent the angle of the ramp.

I assume frictionless, as any friction would complicate matters, and also assume sliding not rolling, as angular momentum/energy would otherwise affect the answer.

3. Jul 17, 2012

### yokialana

Does anybody know if it would work to use the kinematic equation vf2 = vi2 +2ad? I have all the variables to solve for final velocity. But I'm not sutre if it's different because it applies to a curved ramp. Plus this is in the work/energy unit so i don't know why my teacher would want me using that. I'm uber confused. This would be so much easier if I had mass.

4. Jul 18, 2012

### PeterO

Are you saying this ramp is curved?

Does the object leave the ramp travelling horizontally?

You definitely don't need the mass of the object.