Question

What would be the length of a sec. A pendulum at a planet (where acc, due to gravity is $g/4$) if it's length on earth is $l$

• A. $l/2$
• B. $2l$
• C. $l/4$
• D. $4l$

Answer 1

Answer: (C)

$l/4$

Since $T$ (time period) $=2p\sqrt{\frac{l}{g}}$
for seconds pendulum $T=2sec$
Now on the planet the value of acceleration due to gravity is
$g/4$
So for the planet, the length of seconds pendulum $l^{\prime }$ is
$\frac{2sec}{2sec}=\sqrt{\frac{1}{g}\times \frac{g/4}{l^{\prime }}}\Rightarrow l^{\prime }=l/4$