### Class XI

The M.I. of a body about a given axis is 1.2 kg m2m2. Initially the body is at rest. In order to produce a rotational kinetic energy of 1500 joule, an angular acceleration of 25 rad/ sec2sec2 must be applied about that axis for duration of
1. 10 sec
2. 2 sec
3. 4 sec
4. 9 sec
If a gymnast sitting on a rotating stool with his arms outstretched, suddenly lowers his hands
1. his moment of inertia decreases
2. the angular velocity stays constant
3. the angular velocity decreases
4. the angular momentum increases
a body is rotating about z axis with a speed ωω and a point is at a distance of r in the x-y plane then the velocity of the point is
1. 3rω
2. rω/2
3. 2rω
A particle is orbiting in a vertical plane. Its linear momentum will be directed
1. at 45∘∘ to the vertical
2. tangential to the orbit
3. vertically
4. horizontally
A constant torque acting on a uniform circular wheel changes its angular momentum from A0A0 to 4 A0A0 in 4 seconds. The magnitude of the torque is
1. A0
2. 3 A0A0/4
3. 4 A0
4. 12 A0
0
0

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