Question

1 Write down the expressions for centripetal force and angular momentum

2 What are the units of moment of inertia?

3 In Fig.1 show that the tension, T, in the string causing the pulley to rotate is given by

T = m(g-a)

where a is the linear acceleration of the falling mass.

4 In part III, what factors could cause the angular momentum not to be conserved?

Answer 1

1. A centrepetal force is a force that makes a body follow a curved path. It is always perpendicular to direction of motion of object and point towards the center of the curved path. It is given by

where V  is the velocity of object and r is the distance of object from centre.

So

Angular momentum is the rotational equivalent of linear momentum. It is an important quantity in physics because it is a conserved quantity—the total angular momentum of a system remains constant unless acted on by an external torque.

p = linear momentum

L = angular momtum

r = position vector

2. Unit of M.I is

      

3. Since no picture is given in the question, from the question i interpret this to be the diagram

3.

for the pulley to rotate we need T = mg-ma

4. If the mass is rotating about the pivot from which the pulley is hung it wont conserve the angular momentum. also if the mass is oscillating along with sliding it will not conserve the angular momentum.