An insect crawls up a hemispherical surface very slowly. The coefficient of friction between the insect and the surface is $1/3$. If the line joining the centre of the hemispherical surface to the insect makes an angle $\alpha $ with the vertical, the maximum possible value of $\alpha $ so that the insect does not slip is given by

823-1006

  • [AIEEE 2012]
  • [IIT 2001]
  • A

    $\cot \,\alpha  = 3$

  • B

    $\sec \,\alpha  = 3$

  • C

    $\cos ec \,\alpha  = 3$

  • D

    $\cos \,\alpha  = 3$

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