Rotational Motion and Inertia
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Questions and Answers

If the angular momentum of a rotating body is increased by 200%, then its kinetic energy of rotation will be increased by

  • 800% (correct)
  • 100%
  • 400%
  • 200%

    • A ring, a solid sphere, and a thin disc of different masses rotate with the same kinetic energy. Equal torques are applied to stop them. Which will make the least number of rotations before coming to rest?

  • Solid sphere
  • Ring
  • All will make the same number of rotations (correct)
  • Disc

    • The angular velocity of a body is ω = 2ˆi + 3ˆj + 4kˆ and a torque τ = ˆi + 2ˆj + 3kˆ acts on it. The rotational power will be

  • 20 W (correct)
  • 15 W
  • 14 W
  • 17 W

    • A flywheel of moment of inertia 0.32 kg-m² is rotated steadily at 120 rad/sec by a 50 W electric motor. The kinetic energy of the flywheel is

    <p>2304 J</p> Signup and view all the answers

    If the torque acting on a rotating body is doubled, its rotational power will be increased by

    <p>400%</p> Signup and view all the answers

    What happens to a person's moment of inertia when they stretch out their limbs?

    <p>It increases</p> Signup and view all the answers

    What is the difference between translation and rotation?

    <p>Translation is motion along a straight line, rotation is motion around a fixed axis</p> Signup and view all the answers

    What is a characteristic of a rigid body?

    <p>It can rotate with all parts locked together</p> Signup and view all the answers

    What is the purpose of internal forces in a system?

    <p>To enable the particles to form a well-defined system</p> Signup and view all the answers

    What is the main topic of study in this chapter?

    <p>Rotatory motion of a rigid body about a fixed axis</p> Signup and view all the answers

    What is the moment of inertia of a ring of radius 0.5 m and mass 10 kg?

    <p>2.5 kg m^2</p> Signup and view all the answers

    What is the rotational kinetic energy of a rotating body?

    <p>1/2 Iω^2</p> Signup and view all the answers

    What is the torque of an automobile engine that develops 100 kW when rotating at a speed of 1800 rev/min?

    <p>531 N-m</p> Signup and view all the answers

    What is the ratio of rotational kinetic energy to translational kinetic energy for a solid cylinder?

    <p>2/5</p> Signup and view all the answers

    What is the angular velocity of a ring rotating about its diameter with an angular velocity of 20 rad/s?

    <p>20 rad/s</p> Signup and view all the answers

    What is the effect on the moment of inertia of a diver when he stretches out his limbs in mid-air?

    <p>It increases</p> Signup and view all the answers

    What is the characteristic of a rigid body?

    <p>It can rotate with all parts locked together</p> Signup and view all the answers

    What is the difference between translation and rotation?

    <p>Translation is motion in a straight line, rotation is motion in a circle</p> Signup and view all the answers

    Why does the diver's motion change from a high angular speed to a gentle speed when he enters the water?

    <p>Because of the change in his moment of inertia</p> Signup and view all the answers

    What is the purpose of internal forces in a system?

    <p>To enable the particles to form a well-defined system</p> Signup and view all the answers

    A cylindrical shell of radius 0.2 m and mass 5 kg is rotating about its axis with an angular velocity of 15 rad/s. What is its rotational kinetic energy?

    <p>225 J</p> Signup and view all the answers

    A solid sphere of radius 0.4 m and mass 10 kg is rotating about an axis passing through its center with an angular velocity of 20 rad/s. What is its moment of inertia?

    <p>0.48 kg-m²</p> Signup and view all the answers

    A ring of radius 0.3 m and mass 8 kg is rotating about its diameter with an angular velocity of 15 rad/s. What is its angular momentum?

    <p>30 kg-m²/s</p> Signup and view all the answers

    A compound pendulum consists of a rod of length 0.5 m and mass 2 kg, and a point mass of 1 kg attached to its end. What is its moment of inertia about an axis passing through the pivot?

    <p>0.500 kg-m²</p> Signup and view all the answers

    A disc of radius 0.2 m and mass 5 kg is oscillating about an axis passing through its center with a frequency of 2 Hz. What is its rotational kinetic energy?

    <p>12.56 J</p> Signup and view all the answers

    If the moment of inertia of a rotating body is increased by 50%_about a particular axis, then its angular velocity about that axis will be increased by

    <p>25%</p> Signup and view all the answers

    A solid sphere and a thin disc of different masses rotate with the same angular velocity. If the torque acting on them is the same, which will have the higher rotational kinetic energy?

    <p>The solid sphere</p> Signup and view all the answers

    A compound pendulum consists of two point masses connected by a light rod of length 1m. If the moment of inertia of the pendulum about the pivot is 0.5 kg-m², what is the angular frequency of the pendulum?

    <p>1.41 rad/s</p> Signup and view all the answers

    A rotating body oscillates about a stable equilibrium position. If the amplitude of the oscillations is 0.1 rad, what is the maximum angular velocity of the body?

    <p>0.5 rad/s</p> Signup and view all the answers

    If the rotational kinetic energy of a rotating body is increased by 400%, then its angular velocity will be increased by

    <p>200%</p> Signup and view all the answers

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