Question

A bob of pendulum of mass $50 \, g$ is suspended by a string with the roof of an elevator. If the lift is falling with a uniform acceleration of $5 \, m \, s^{- 2},$ the tension in the string is $\left(g = 10 \, m \, s^{- 2}\right)$

• A. $0.5 \, N$
• B. $0.225 \, N$
• C. $0.25 \, N$
• D. $0.025 \, N$

Answer 1

Answer: (C)

Here, mass of bob, $m=50 \, g$
$=0.05 \, kg$
Since, the lift is falling downward with a uniform acceleration of $5ms^{- 2}$ , hence tension in the string,
$T=m\left(g - a\right)$
$=0.05\left(10 - 5\right)$
$=0.05\times 5$
$=0.25 \, N$