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Question 30770
JEE Physics · Hard

Gravitation: Advanced — Tunnelling Through Earth MCQ

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Advanced — Tunnelling Through EarthHardQuestion 30770

Question

A tunnel is drilled straight through Earth's centre. A ball dropped in from one end undergoes SHM with period:
  1. A
    84 min
    Correct
  2. B
    24 hours
  3. C
    42 min
  4. D
    12 hours

Correct answer

84 min

Explanation

T = 2π√(R/g) = 2π√(6.4×10⁶/10) ≈ 84 min — same as a surface-skimming satellite! This is a remarkable coincidence from Earth's uniform density approximation.

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