So,
"a uniform steel rod of length 1.20 meters and mass 6.40 kg has attached to each end a small ball of mass 1.06 kg. The rod is constrained to rotate in a horizontal plane about a vertical axis through its midpoint."
There's more to the question, but the only part I'm really stuck on is Inertia. My friend tried to explain to me that the inertia of the system here is
I(tot) = I(ball) + I(rod)
= MR^2 + (1/12)MR^2
= M(L/2)^2 + (1/12)M(L)^2
...My question is why you can assume that the ball apparently has a radius of L/2. That seems like such an illogical, random assumption to make.
1 answer
The ball doesn't have a radius of L/2 but it sits at a radius of L/2 from the axis of rotation. Inertia looks at the position of a certain mass from the axis of rotation.
1 answer