Q102 / 125 · BITSAT 2014 · Physics

A tunnel has been dug through the centre of the earth and a ball is released in it. It executes S.H.M. with time period

  • A
    42 minutes
  • B
    1 day
  • C
    1 hour
  • Correct answer
    D
    84.6 minutes

Solution

$\mathrm{T}=2 \pi \sqrt{\frac{\mathrm{R}}{\mathrm{g}}}=2 \pi \sqrt{\frac{64 \times 10^{6}}{9.8}}$ $=2 \times \frac{22}{7} \times \frac{8 \times 10^{3}}{7 \times \sqrt{2}}$ $=\frac{\sqrt{2} \times 22 \times 8 \times 1000}{49 \times 60} \min =84.6 \mathrm{~min}$

Hence, the correct answer is option: 'D'.

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