# Kinetic rotational energy problem

1. Jan 30, 2012

### spaghetti3451

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

A diatomic molecule can be modeled as two point masses, m1 and m2, slightly separated. If the molecule is oriented along the y-axis, it has kinetic energy K when it spins about the x-axis. What will its kinetic energy (in terms of K) be if it spins at the same angular speed about

(a) the z-axis
(b) the y-axis?

2. Relevant equations

K = 0.5Iω2

3. The attempt at a solution

(a) I stays the same as the atoms are the same perpendicular distance from the origin. So the kinetic energy = K.

(b) I = 0 as the perpendicular distance between each atom and the rotation axis (the y-axis) is 0. So, kinetic energy = 0.

It would help me if you comment on my solution.

2. Jan 31, 2012

### Simon Bridge

Looks good to me.
Was there anything in particular you were concerned about?

3. Feb 1, 2012

### spaghetti3451

Oh no, just wanted to know if my answers were good. Thanks, by the way!

4. Feb 1, 2012

### Simon Bridge

No worries.
Looks like you need to develop ways to decide for yourself if your answers are good.