- #1

mathildej

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## Homework Statement

Two balls are connected together and fall through air. They also rotate around the center of mass. I'm supposed to find an equation for the torque of air resistance through the center of mass.

Fk= Force due to air resistance on each of the balls

w=angular velocity

Vcm=velocity of the center of mass

M=mass of each ball

R=radius of each ball

Kv=constant

T=torque

Icm=moment of inertia in the center of the mass

Ia=Ib= moment of inertia for each ball

r= position of the ball relative to the center of mass

## Homework Equations

Ia=Ib=(2/5)MR^2

Fk=-2Kv*Vcm

Icm=(14/5)M(R^2)

Va=Vcm+w X r

Vb=Vcm - w X r

This is the answer I'm supposed to get: T=-2Kv*w*R^2

## The Attempt at a Solution

I have tried sooo many different ways to get this.

And still I have no idea. Can anyone help me?