System of Particles and Rotational Motion · Question 73

A uniform rod AB of length l and mass m is free to rotate about point A. The rod is released from rest in the horizontal position. Given that the moment of inertia of the rod about A is ml23, the initial angular acceleration of the rod will be

1. mgl2
2. 32gl
3. 3g2l
4. 2g3l

The moment of inertia of a uniform circular disc of radius R and mass M about an axis touching the disc at its diameter and normal to the disc

1. 12MR2
2. MR2
3. 25MR2
4. 32MR2

The moment of inertia of a uniform circular disc of radius R and mass M about an axis passing through the edge of the disc and normal to the disc is

1. MR2
2. 12MR2
3. 32MR2
4. 72MR2

A drum of radius R and mass M, rolls down without slipping along an inclined plane of angle . The frictional force

1. dissipates energy as heat
2. decreases the rotational motion
3. decreases the rotational and translational motion
4. converts translational energy to rotational energy.

Two bodies have their moments of inertia I and 2I respectively about their axis of rotation. If their kinetic energies of rotation are equal, their angular velocity will be in the ratio

1. 2 : 1
2. 1 : 2
3. 2 : 1
4. 1 : 2

Three particles, each of mass m gram, are situated at the vertices of an equilateral triangle ABC of side l cm (as shown in the figure). The moment of inertia of the system about a line AX perpendicular to AB and in the plane of ABC, in gram-cm2 units will be [figure]

1. 34ml2
2. 2ml2
3. 54ml2
4. 32ml2

Consider a system of two particles having masses m1 and m2. If the particle of mass m1 is pushed towards the mass centre of particles through a distance d, by what distance would the particle of mass m2 move so as to keep the mass centre of particles at the original position?

1. m1m1 + m2d
2. m1m2d
3. d
4. m2m1d

A wheel having moment of inertia 2 kg m2 about its vertical axis, rotates at the rate of 60 rpm about this axis. The torque which can stop the wheel's rotation in one minute would be

1. 2 15 N m
2. 12 N m
3. 15 N m
4. 18 N m

A round disc of moment of inertia I2 about its axis perpendicular to its plane and passing through its centre is placed over another disc of moment of inertia I1 rotating with an angular velocity about the same axis. The final angular velocity of the combination of discs is

1. I2 I1 + I2
3. I1 I1 + I2
4. (I1 + I2) I1

The ratio of the radii of gyration of a circular disc about a tangential axis in the plane of the disc and of a circular ring of the same radius about a tangential axis in the plane of the ring is

1. 2 : 3
2. 2 : 1
3. 5 : 6
4. 1 : 2