# Physics

posted by
**CJ** on
.

A woman stands at the center of a platform. The woman and the platform rotate with an angular speed of 4.00 rad/s. Friction is negligible. Her arms are outstreched, and she is holding a dumbbell in each hand. In this position the total moment of inertia of the rotating system (platform, woman, and dumbbells) is 5.40kg.m2. By pulling in her arms, she reduces the moment of inertia to 4.40kg*m2. Find her new angular speed.

Apply the law of conservation of angular momentum.

I1*w1 = I2*w2

I2/I1 is the moment of inertia ratio. It equals w1/w2. Solve for w2.

w1 = 4.00 rad/s