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JEE Main 2020 (6 Sep, Shift 1) · Two-Body Friction

Two-Body Friction question from JEE Main 2020 (6 Sep, Shift 1)

Q7JEE Main 2020 · 6 SEP · SHIFT 1Medium

Two-Body Friction

An insect is at the bottom of a hemispherical ditch of radius 1 m. It crawls up the ditch but starts slipping after it is at height h from the bottom. If the coefficient of friction between the ground and the insect is 0.75, then h is:

(g = 10 ms–2)

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Answer: (c)

  1. At position angle θ\theta from the vertical, the insect slips when tan⁡θ=μ=0.75\tan\theta = \mu = 0.75.
  2. So cos⁡θ=0.8\cos\theta = 0.8.
  3. h=R(1−cos⁡θ)=1×(1−0.8)h = R(1 - \cos\theta) = 1 \times (1 - 0.8)
  4. h=0.2h = 0.2 m, so the answer is (c).
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