AP®PhysicsCollege BoardPhysics 1: Algebra-BasedFlashcardsUnit 6: Energy & Momentum of Rotating SystemsRotational Kinetic Energy, Torque & Work

Rotational Kinetic Energy, Torque & Work (College Board AP® Physics 1: Algebra-Based): Flashcards

1/13

0Still learning

Know0

Cards in this collection (13)

  • State the equation for rotational kinetic energy.

    K = \frac{1}{2} I \omega^{2}

    • K = rotational kinetic energy (J)

    • I = rotational inertia (kg·m2)

    • \omega = angular velocity (rad/s)

  • Is rotational kinetic energy a scalar or a vector?

    It is a scalar quantity, like other forms of energy.

  • State the equation for the rotational inertia of a single point mass about a fixed axis.

    I = m r^{2}

    • I = rotational inertia (kg·m2)

    • m = mass of the object (kg)

    • r = distance to the axis of rotation (m)

  • At different points on a rotating body the linear velocity varies, but the .......... is the same at all points.

    At different points on a rotating body the linear velocity varies, but the angular velocity is the same at all points.

  • State the equation for the total kinetic energy of a rigid system that rotates and moves forward.

    K_{\text{total}} = K_{r} + K_{t} = \frac{1}{2} I \omega^{2} + \frac{1}{2} m v^{2}

    • K_{r} = rotational kinetic energy about the center of mass (J)

    • K_{t} = translational kinetic energy of the center of mass (J)

    • m = mass (kg)

    • v = speed of the center of mass (m/s)

  • State the two conditions for Newton's laws for rotational motion to remain valid for a rigid circular object that also moves forward.

    • The axis of rotation passes through the object's center of mass

    • The axis of rotation keeps a fixed direction

  • True or False?

    A rigid system whose center of mass is at rest cannot have rotational kinetic energy.

    False.

    Individual points in the system still have linear speed, so a system such as a flywheel has rotational kinetic energy about a stationary center of mass.

  • State the equation for the work done by a torque.

    W = \tau ∆\theta

    • W = work done (J)

    • \tau = torque (N·m)

    • ∆\theta = angular displacement (rad)

  • How can equal amounts of work be done on a rigid system using different torques?

    • A smaller torque over a greater angle of rotation

    • A larger torque over a smaller angle of rotation

  • In linear systems, work done is the product of force and ...........

    In linear systems, work done is the product of force and linear displacement.

  • True or False?

    A larger torque always does more work on a rigid system.

    False.

    Work depends on the angular displacement as well as the torque, since W = \tau ∆\theta.

  • What two quantities are equal to the area under a torque-angular position graph?

    • The work done on the system by the torque

    • The change in kinetic energy of the system, when the graph shows the net torque

  • What does an area below the axis on a torque-angular position graph represent?

    Negative work, meaning energy is removed from the system.

Sign up to unlock flashcards
or

By signing up you agree to our Terms and Privacy Policy

Previous:Newton’s First & Second Law in Rotational FormNext:Angular Momentum & Angular Impulse