# Homework Help: Solid disk rolling

1. Apr 30, 2013

### NathanLeduc1

1. The problem statement, all variables and given/known data
A solid disk of mass m and radius R rolls without slipping with a velocity v. Assuming it doesn't slip, how far vertically will it roll up an incline?

2. Relevant equations
I=0.5mr2
E=0.5Iω2
KE=0.5mv2
PE=mgh

3. The attempt at a solution
I'm thinking that we need to find the height h when the kinetic energy is converted to potential energy. So:
0.5Iω2+mv2=mgh
0.5*0.5mr2ω2+mv2=mgh
0.25r2ω2+v2=gh
h=(0.25r2ω2+v2)/g
Is that right? I feel weird because I still have ω in there.

2. Apr 30, 2013

### SammyS

Staff Emeritus
What's the relationship between v and ω ?

3. Apr 30, 2013

### NathanLeduc1

Ah, either you're a genius or I'm dumb. Probably both. Thank you.

I got a final answer of (1.2*v^2)/g = h.

4. Apr 30, 2013

### NathanLeduc1

Oops, 1.25... ((5/4)(v^2))/g = h

5. May 1, 2013

### SammyS

Staff Emeritus
Probably neither.

I considered a lengthier reply to your Original Post, but then though I'd see what you could do with a fairly subtle hint/question. From that, you completed the exercise. I commend you for that.

You might be surprised at how many people need to be led by the nose, step-by-step to an answer.