Question

thick rod is rotating (without friction) about an axis that is perpendicular to the rod and passes through its center. The rotational inertia of the rod is 1.8 kg•m2. A 4.2-kg cat is standing at the center of the rod. When the cat is at the center of the rod, the angular speed is 4.8 rad/s. The cat then begins to walk along the rod away from the center of the rod. The cat stops at a distance of 0.4 m from the rod's center. Treat the cat as a particle.

a) As the cat walks away from the center of the rod, does the angular momentum of the cat-rod system increase, decrease, or stay the same?b) As the cat walks away from the center of the rod, does angular speed increase, decrease, or stay the same?c) What is the rotational inertia of the rod-cat system when the cat is 0.4 m from the rod's center?d) What is the angular speed of the rod when the cat is 0.4 m from the rod's center?

Answer #1

1. As the cat walks away from the center of the rod, the angular
momentum of cat-rod system will remain constant as there is
**no external torque** act on the system.

2. As the cat walks away from the center of the rod, does
angular speed will **decrease** because the moment of
inertia will increase and to keep angular momentum constant angular
speed will decrease.

4.Angular speed=3.495rad/sec.

3. Rotational inertia=2.472kgm^2

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