Question

1. In each question: you place mass m on the mass holder, and released the system from rest. The system includes two pulleys and a long rod with two point masses on it. If you increase m, the mass on the mass holder, what happens to the following quantities: - a, the angular accelertion of the pulley and I, the moment of inertia of the pulleys-plus-rod system.

Do they increase, decease, or remain the same?

2.  If you move the two masses attached to the rotating rod away from the center of mass of the rod, what happens to the following quantities:
- a, the angular accelertion of the pulley.
- I, the moment of inertia of the pulleys-plus-rod system.

Do they increase, decease, or remain the same?

Answer 1

When you add mass to the mass holder, you increase the force on the system (F=ma). Your pulley+rod system gets pulled harder. This increases the angular acceleration of the pulley and its angular velocity. Because L=i w (angular momentum = moment of inertia x angular velocity) your angular momentum should also increase.

answer for a
6.-a increases, I increases

When you move the point masses farther from the center point you effectively increase the systems moment of inertia (i) and because L=i w, the angular momentum will decrease for the same w. When i increases, this makes the system harder to rotate meaning it requires more pulling force to rotate. So your 'a' decreases. Ever notice the technique used by figure skaters? When they move their arms out they rotate slowly because they increased their moment of inertia and thus decrease their angular acceleration and velocity.

Answer b
2.-a decreases, I decrease