System of Particles and Rotational Motion · Question 81

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

A ball rolls without slipping. The radius of gyration of the ball about an axis passing through its centre of mass is K. If radius of the ball be R, then the fraction of total energy associated with its rotational energy will be

1. K2 + R2R2
2. K2R2
3. K2K2 + R2
4. R2K2 + R2

A solid cylinder of mass M and radius R rolls without slipping down an inclined plane of length L and height h. What is the speed of its centre of mass when the cylinder reaches its bottom ?

1. 2gh
2. 34gh
3. 43gh
4. 4gh

A thin circular ring of mass M and radius r is rotating about its axis with a constant angular velocity . Four objects each of mass m, are kept gently to the opposite ends of two perpendicular diameters of the ring. The angular velocity of the ring will be :

1. M 4m
2. M M + 4m
3. (M + 4m) M
4. (M - 4m) M + 4m

A rod of length 3 m and its mass acting per unit length is directly proportional to distance x from one of its end then its centre of gravity from that end will be at :

1. 1.5 m
2. 2 m
3. 2.5 m
4. 3.0 m

A point P is considered at contact point of a wheel on ground which rolls on ground without slipping then value of displacement of point P when wheel completes half of rotation (if radius of wheel is 1 m)

1. 2 m
2. 2+4 m
3. m
4. 2+2 m

A solid sphere of radius R is placed on smooth horizontal surface. A horizontal force F is applied at height h from the lowest point. For the maximum acceleration of centre of mass, which is correct ?

1. h = R
2. h = 2R
3. h = 0
4. no relation between h and R.

A disc is rotating with angular speed . If a child sits on it, what is conserved

1. linear momentum
2. angular momentum
3. kinetic energy
4. potential energy

A circular disc is to be made by using iron and aluminium so that it acquired maximum moment of inertia about geometrical axis. It is possible with

1. aluminium at interior and iron surround to it
2. iron at interior and aluminium surround to it
3. using iron and aluminium layers in alternate order
4. sheet of iron is used at both external surface and aluminium sheet as internal layers.