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13. oscillations — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics13. oscillations1 Mark
MCQ
A simple pendulum suspended from the ceiling of a stationary lift has period $T_0$. When the lift descends at steady speed, the period is $T_1$, and when it descends with constant downward acceleration, the period is $T_2$. Which one of the following is true?
  • A
    $T_0=T_1=T_2$
  • ✓
    $T_0=T_1$
  • C
    $T_0=T_1 > T_2$
  • D
    $T_0 < T_1 < T_2$
✓

Answer

Correct option: B.
$T_0=T_1$
b
(b)

Pseudo force only when there is an acceleration.

Hence $T_0=T_1$ as there is uniform downward motion.

When it moves downward with a steady acceleration then pseudo force acts upwards, reducing net ' $g$ '

Since $T_2=2 \pi \sqrt{\frac{1}{g_{\text {net }}}}$

When $g$ reduces time period $T_2$ increases

$T_0=T_1 < T_2$

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