# Inertia question

by sagebum
Tags: inertia
 P: 5 1. The problem statement, all variables and given/known data Which is harder to rotate? A rod with a mass (m1) in the center, or a rod with two masses (m2)at the ends. Assume mass m1 = 2*m2, so the total masses of rod+masses are equal. I am rotating the masses at the center. My professor said that the one with the mass in the center is harder to rotate, but I dont understand how he explained it. I actually thought the one with the mass in the center was easier to rotate. Can someone explain why the one with the mass in the center is harder to rotate? Is it because if we were to rotate each to the same angular velocity, it would take more work to get the first rod to that angular velocity? Relevant equations. I think I'd use Kr = I $$\omega^{2}$$ and if they go up to the same angular velocities, it requires more work? It doesn't seem right, because if the I of the first rod is lower, so the Kr would be lower, so that means the work required to get it to that speed was lower? I don't see why the one with the mass in the center is easier to rotate.