A $20\, kg$ block is initially at rest on a rough horizontal surface. A horizontal force of $75 \,N$ is required to set the block in motion. After it is in motion, a horizontal force of $60\, N$ is required to keep the block moving with constant speed. The coefficient of static friction is

  • A

    $0.38$

  • B

    $0.44$

  • C

    $0.52$

  • D

    $0.6$

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