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⚛️ Physics  ·  Oscillations  ·  NEET & JEE

When a simple pendulum is in a lift that accelerates upward with acceleration a, its period:

Answer: decreases.

  • A decreases
  • B increases
  • C remains unchanged
  • D becomes zero

Correct answer: A. decreases

Explanation: Effective gravity becomes g + a, so T = 2π√(L/(g+a)) decreases.

Displacement, Velocity, Acceleration in SHMx(t)v(t)a(t)v leads x by 90°; a is exactly out of phase with x (a = −ω²x)

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.

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