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**A 1.0 kg ball and a 2.0 kg ball are connected by a 1.0-m-long rigid, massless rod. The rod is rotating cw about its center of mass at 20 rpm. What torque will bring the balls to a halt in 5.0 s?**

**I used (m1x1+m2x2)/(m1+m2) to solve for the center of mass (2/3 meters from the 1kg weight). Then I used that to solve for the moment of inertia, using I= m1r1^2+m2r2^2, and I got I=1. I know [tex]\alpha[/tex]=[tex]\tau[/tex]/I, and [tex]\alpha[/tex]=([tex]\omega[/tex]_final - [tex]\omega[/tex]_initial) / time. I plugged in my known values (0 rps, 1/3rps, and 5 seconds, respectively) and got -0.1333 for [tex]\alpha[/tex]. Then I multiplied [tex]\alpha[/tex] by I and got -0.1333, which is wrong. I don't know where I screwed up. Any help would be greatly appreciated. Thanks**

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