Two heavy cylindrical masses are placed at opposite ends of a platform that rotates around its center. A torque is applied to the platform's axle by means of a string. The string passes over a pulley and a mass hangs from the other end of the string.

The system is released from rest, and the platform begins to rotate with a particular angular acceleration.

If the experiment is performed a second time with the masses moved closer to the center of the platform, what will happen?

1. The angular acceleration will decrease. (2/33) (6%)
2. The angular acceleration will stay the same. (3/33) (9%)
3. The angular acceleration will increase. (28/33) (85%)

According to Newton's Second Law, Στ = I α . The torque from the hanging mass is about the same in the two cases. Moving the masses closer to the center reduces the moment of inertia, which increases the angular acceleration.