Circular Motion

AP Physics 1· difficulty 3/5

A 1.0 kg1.0~\text{kg} ball at the <strong>top</strong> of a vertical loop of radius 2.0 m2.0~\text{m} moves at 8.0 m/s8.0~\text{m/s}. Using g10 m/s2g \approx 10~\text{m/s}^2, what is the magnitude of the normal force from the track on the ball?

  • A

    42 N42~\text{N}

  • B

    32 N32~\text{N}

  • C

    22 N22~\text{N}

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  • D

    52 N52~\text{N}

Explanation

At the top, both gravity and normal point toward the center (down): N+mg=mv2/rN=(1)(64)/2(1)(10)=3210=22 NN + m g = m v^2/r \Rightarrow N = (1)(64)/2 - (1)(10) = 32 - 10 = 22~\text{N}.

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