Class XI

A body having moment of inertia about its axis equal to 3 kg m2m2 is rotating with angular velocity equal to 3 rad/s. The kinetic energy of this rotating body is the same as that of a body of mass 27 kg moving with a speed of
  1. 1.0 m/s
  2. 1.5 m/s
  3. 0.5 m/s
  4. 2.0 m/s
A fan of moment of inertia 0.3 kg m2m2is to run up to a working speed of 0.5 revolution per second. Indicate the correct value of the angular momentum of the fan
  1. 3( kg ×× m2m2) / sec
  2. 6 kg ×× m2m2/sec
  3. (ππ /6) (kg ×× m2m2) / sec
  4. 0.3 ππ kg ×× m2m2 / sec
A dancer on ice spins faster when she folds her hands. This is due to
  1. increase in energy and decrease in angular momentum
  2. decrease in friction at the skates
  3. constant angular momentum and increase in kinetic energy
  4. increase in energy and increase in angular momentum
A child swinging on a swing in a sitting position stands up. Then, the time period of the swing will
  1. Decrease
  2. Remains the same
  3. Increase
  4. Increase if the child is tall and decrease if the child is short.
The angular velocity of a body changes form 1 rev / sec to 25 rev/sec. without applying any external torque. The ratio of the radii of gyration in the two cases is
  1. it is 1: 25
  2. it is 1: 5
  3. it is 25:1
  4. it is 5:1
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