# Rotaional Inertia of a Thin Rod

1. Apr 1, 2009

### Oijl

1. The problem statement, all variables and given/known data
Calculate the rotational inertia of a meter stick, with mass 0.68 kg, about an axis perpendicular to the stick and located at the 21 cm mark. (Treat the stick as a thin rod.)

2. Relevant equations
I = integral of r squared with respect to mass

3. The attempt at a solution
?

2. Apr 1, 2009

### Pythagorean

so you want to find the mass of the object as a function of the distance from the axis. We can assume the the density is constant, so we could write:

dm = pdV

where dm is the mass differential from the integral, p the density (a constant) and dV the volume.

But some parts of the volume are constant, so you can further manipulate this equation. Can you see where to go from here?