(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

You're holding a massless stick with a mass (m) on it at a distance (d) from your hand. You move the mass to 2d from your hand, how much larger force do you have to apply with your hand to keep the stick stable if the force you were applying before was F?

2. Relevant equations

Torque = r cross F.

Torque = Rotational inertia * angular acceleration

3. The attempt at a solution

Since you have to apply the same torque as gravity is on the mass, it should be twice the force because:

r * (2F) = (2r) * F.

But my teacher said since Rotational Inertia = m * (r)^2, the force you have to apply have to be 4 times as before because m * (2d) ^ 2 is 4 times as the rotational inertia before.

Can any1 tell me if it's twice or quadruple, with work?

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# Homework Help: Torque and rotational inertia

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