Conservation of Energy

AP Physics 1· difficulty 3/5

A 2 kg2~\text{kg} box slides 5 m5~\text{m} across a floor with μk=0.30\mu_k = 0.30 and starts at 4.0 m/s4.0~\text{m/s}. Using g10 m/s2g \approx 10~\text{m/s}^2, its final speed is

  • A

    3.0 m/s3.0~\text{m/s}

  • B

    2.0 m/s2.0~\text{m/s}

  • C

    00

    check_circle
  • D

    1.0 m/s1.0~\text{m/s}

Explanation

Friction work: Wf=μkmgd=(0.30)(2)(10)(5)=30 JW_f = \mu_k m g d = (0.30)(2)(10)(5) = 30~\text{J}. Initial KE: 12(2)(16)=16 J\tfrac{1}{2}(2)(16) = 16~\text{J}. Since Wf>K0W_f > K_0, the box stops before 5 m5~\text{m}.

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