A simple pendulum suspended from the ceiling of a lift has time period T when the lift is at rest. When the lift falls freely, the time period is_________________?
Correct answer: A. Infinite
- A. Infinite
- B. T/g
- C. Zero
- D. g/T
Explanation
For a pendulum, T = 2π√(L/g_eff). During free fall, the lift and pendulum accelerate downward together, so the effective gravity g_eff becomes 0 m/s²; the formula then gives T tending to infinity. A student may choose c by thinking zero effective gravity stops the time period, but the pendulum no longer has a restoring force and cannot complete oscillations.
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About Simple Harmonic Motion
Simple harmonic motion is oscillation in which acceleration is directly proportional to displacement and directed toward the equilibrium position. Work includes displacement, velocity, acceleration, phase, period, frequency, amplitude and energy, with applications to springs and simple pendulums. The restoring force and the conditions for SHM distinguish it from general periodic motion.
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