AP Physics 1 · Topic 6.3

Angular Momentum and Angular Impulse Practice

Part of Energy and Momentum of Rotating Systems.(TOP-6.C)

Practice questions

7

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Sample questions

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  1. Sample 1difficulty 1/5

    A flywheel of moment of inertia 2.0 kg⋅m22.0~\text{kg·m}^2 spins at 15 rad/s15~\text{rad/s}. What is its angular momentum?

    • A

      300 kg⋅m2/s300~\text{kg·m}^2\text{/s}

    • B

      7.5 kg⋅m2/s7.5~\text{kg·m}^2\text{/s}

    • C

      30 kg⋅m2/s30~\text{kg·m}^2\text{/s}

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    • D

      17 kg⋅m2/s17~\text{kg·m}^2\text{/s}

    Why

    L=Iω=(2.0)(15)=30 kg⋅m2/sL = I\omega = (2.0)(15) = 30~\text{kg·m}^2\text{/s}.

  2. Sample 2difficulty 1/5

    Angular momentum has units

    • A

      kg/m\text{kg/m}

    • B

      kg⋅m2/s\text{kg·m}^2/\text{s}

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    • C

      kg⋅m2/s2\text{kg·m}^2/\text{s}^2

    • D

      N⋅m\text{N·m}

    Why

    [L]=[I][ω]=kg⋅m2rad/s=kg⋅m2/s[L] = [I][\omega] = \text{kg·m}^2 \cdot \text{rad/s} = \text{kg·m}^2/\text{s} (rad is dimensionless).

  3. Sample 3difficulty 2/5

    A spinning disk on the floor is viewed from above and rotates clockwise. Its angular-momentum vector points

    • A

      Tangentially

    • B

      Up

    • C

      Down

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    • D

      Toward the center

    Why

    Right-hand rule: fingers curl with rotation, thumb gives L\vec L. CW from above → L\vec L down.

  4. Sample 4difficulty 2/5

    A 0.50 kg0.50~\text{kg} particle moves in a horizontal circle of radius 0.40 m0.40~\text{m} at 3.0 m/s3.0~\text{m/s}. Its angular momentum about the center is

    • A

      1.5 kg⋅m2/s1.5~\text{kg·m}^2/\text{s}

    • B

      2.4 kg⋅m2/s2.4~\text{kg·m}^2/\text{s}

    • C

      0.20 kg⋅m2/s0.20~\text{kg·m}^2/\text{s}

    • D

      0.60 kg⋅m2/s0.60~\text{kg·m}^2/\text{s}

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    Why

    L=mvr=(0.50)(3.0)(0.40)=0.60 kg⋅m2/sL = m v r = (0.50)(3.0)(0.40) = 0.60~\text{kg·m}^2/\text{s}.

  5. Sample 5difficulty 2/5

    A disk spins counterclockwise when viewed from above. By the right-hand rule, the direction of its angular-momentum vector is

    • A

      Upward

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    • B

      Downward

    • C

      Counterclockwise along the rim

    • D

      Clockwise along the rim

    Why

    Curl the right-hand fingers along the rotation direction; the thumb points along L\vec L. For CCW-viewed-from-above, the thumb points <strong>up</strong>.