Question 196: Centre of Mass and Rotational Motion

Question

A mass M hangs on a massless rod of length l which rotates at a constant angular frequency. The mass M moves with steady speed in a circular path of constant radius. Assume that the system is in steady circular motion with constant angular velocity $$\omega$$. The angular momentum of M about point A is L
A
which lies in the positive z direction and the angular momentum of M about point B is L
B
. The correct statement for this system is :

Accepted Answer

Net force on M is towards A, hence torque is zero
about A.
$${\overrightarrow L _A} = \overrightarrow r  	imes \overrightarrow p $$
as $$r \bot p$$ so L
A
= constant

Answer

L
A
is constant, both in magnitude and direction

Answer

L
B
is constant in direction with varying magnitude

Answer

L
B
is constant, both in magnitude and direction

Answer

L
A
and L
B
are both constant in magnitude and direction

Centre of Mass and Rotational Motion

Choose the correct answer: