# Homework Help: Find translational Ke Rotational Ke

1. Dec 9, 2006

### blackout85

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

A basketball weighs 500grams or (.5 kg) it has a radius of 10cm (.10 m) and is rolling at 2.0 m/s. Find translational Ke Rotational Ke Translational momentum and Rotational momentum.

2. Relevant equations
translational ke= 1/2mv^2
rotational ke = 1/2Iw^2 ( I am unsure of what inertia equation to use for a basketball)
Translational momentum= mv^2
rotational ke = iw
3. The attempt at a solution

Translational ke = 1/2 mv^2= .5(.5kg)(2.0m/s)^2= 1 J
I think I know how to do the equations I just dont know what equation to use for the rotational inertia for a basketball, if someone could help me on that. Thanks
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Dec 9, 2006

### Andrew Mason

I think you mean L = angular momentum = $I\omega$
The moment of inertia of a solid or hollow sphere is a calculus problem. It works out to $\frac{2}{5}MR^2$ for a solid sphere and $\frac{2}{3}MR^2$ for a hollow sphere (see the http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html#cmi"). Which one would you use?

How do you determine the rotational speed from the translational speed? ie. how long does it take the ball to roll 360 degrees or $2\pi$ radians?

AM

Last edited by a moderator: Apr 22, 2017
3. Dec 9, 2006