# A little help , rotational and youngs modulus

1. Nov 21, 2008

### invisiblewar

A little help plz, rotational and youngs modulus

1. The problem statement, all variables and given/known data
A solid Ball with a mass of 3kg and r=1m is suspended in the center of a hollow ball of mass=1kg and r=3m. It is placed at rest on a 33 degree incline. after rolling 1km along the incline whats the final tangetial velocity? whats the objects final angular momentum?

2. Relevant equations
I know i need I=mr^2
and Im pretty sure this is a conservative problem so KEi+PEi=KEf+PEf
KE=Iw^2 and KE=1/2mv^2
PE=mgh or mgr

3. The attempt at a solution
Im not too sure how to input the problem at all...should I combine the two moments of Inertia? then go from there or should they both be done seperately? This problem is killing me

2. Nov 21, 2008

### tiny-tim

Hi invisiblewar!

(have an omega: ω )
Yes, moments of inertia (about the same axis) are scalars, so you just add them.

(and it's rolling, so don't forget to find the equation relating v to ω )

3. Nov 21, 2008

### invisiblewar

Re: A little help plz, rotational and youngs modulus

awesome thanks so much