Question

A pendulum is swinging in an elevator. Its period will be greatest when the elevator is

• A. Moving upwards at constant speed
• B. Moving downwards
• C. Moving downwards at constant speed
• D. Accelerating downwards

Answer 1

The correct option is D Accelerating downwards

Time period of a simple pendulum is given by
$T=2\pi \sqrt{\frac{l}{g}}$ or $T\propto \sqrt{\frac{l}{g}}$
when the elevator is accelerating downwards, the net gravitational acceleration is $(g-a)$, so, the time period when elevation is accelerating downwards, is greatest.