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 (A)</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% (D)</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 (C)</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 (A)</p> Signup and view all the answers

What is a characteristic of a rigid body?

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

What is the rotational kinetic energy of a rotating body?

<p>1/2 Iω^2 (A)</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 (D)</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 (D)</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 (B)</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 (D)</p> Signup and view all the answers

What is the characteristic of a rigid body?

<p>It can rotate with all parts locked together (D)</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 (B)</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 (A)</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 (D)</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 (B)</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 (C)</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 (B)</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 (C)</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 (D)</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% (D)</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 (A)</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 (B)</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 (C)</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% (D)</p> Signup and view all the answers

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