# Height of Slope? Mass unknown

1. Feb 3, 2015

### Ivar

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

A box is on top of a slope. The slope has NO FRICTION. V0 = 0 m/s, V = 4m/s.

MASS IS UNKNOWN

What is the height of the slope?
2. Relevant equations
Equation for energy (i think)

3. The attempt at a solution
I attempted to find the accelleration, but I do not know what the accelleration is for an object running down a slope with no friction.
The only force applying to the box is gravity, I think.

I am new to Physics. I tried solving it, but to no avail.
I know this can be solved without knowing the mass, but I don't know how! Help?

2. Feb 3, 2015

### jake jungle

KE at bottom should be equal to PE on the top of the slope

3. Feb 3, 2015

### Ivar

Yes. That I know. Bit how does this help me find the height of the Slope?

And what is the accelleration of an object running down a slope with no friction?

4. Feb 3, 2015

### jake jungle

KE= mv^2 / 2 = mgh =PE .
mass is omitted in the equation , therefore you can find h .
the acceleration = F / m , you should find which component of gravity actually makes the mass running down the slope , then devide m , you got acceleration

5. Feb 3, 2015

### Staff: Mentor

Hi Ivar. Welcome to Physics Forums.

Jake Jungle has shown one method of getting the answer to your problem using energy conservation. But, it is not the only method, and maybe you are not that comfortable with using energy conservation. If not, have you considered drawing a free body diagram, and showing the forces acting on the box in your free body diagram?

Chet