Answer: 84.6 minutes.
- A 84.6 minutes
- B 24 hours
- C 9.8 s
- D 1 hour
Correct answer: A. 84.6 minutes
Explanation: The restoring force inside Earth = -GMmr/R³ (proportional to r). T = 2π√(R/g) ≈ 2π√(6.4×10⁶/10) ≈ 5078 s ≈ 84.6 minutes.
In SHM, displacement and velocity are 90° out of phase (v is maximum when x=0, and zero when x is extreme), while acceleration is always exactly opposite in sign to displacement, consistent with a = −ω²x.
Concept context
Simple harmonic motion, spring-mass, pendulum, energy in SHM, and resonance.