Speed of a ball rolling down an incline

[captainjack]

Homework Statement

A hollow basketball rolls down a 30$$\circ$$ incline. If it starts from rest, what is its speed after it's gone 8.4 m along the incline?

Homework Equations

v=$$\omega$$R

The Attempt at a Solution

I don't really know where to start with this. I've done similar problems, but I was given the mass of the rolling object. What equations would I need to manipulate so that I don't need the mass or radius of the basketball? I feel like this is a fairly simple problem, but my professor never showed us how to do one without mass, and the book doesn't explain either.

I know that to receive help here I'm supposed to have made an attempt at the problem, but I would greatly appreciate any help. Even if it is just a few equations that I should be looking at.

 

[tiny-tim]

hi captainjack!

(have an omega: ω )

call the mass "m" and the radius "r", and use conservation of energy, with your rolling constraint v = ωr …

what do you get? ​

 

[ehild]

Just call the mass m, and the radius of the ball be R. They will cancel.
Conservation of energy is very useful for such problems. The ball rolls, so it has both translational and rotational kinetic energy, and rolling means that the speed of translation and the angular speed of rotation are related as v=wR.

Edit:Tiny-tim beat me ...

ehild

 

[captainjack]

Thank you so much (: figured it was some super important rule I was forgetting XP