A pendulum makes 20 oscillations in 4.0s on earth and 40 oscillation on planet X. What is the acceleration due to gravity on planet X?

4g

Explanation:

Given

The time on earth is 4 s for 20 oscillations

i.e. time period for one oscillation is

for planet X it is 40 oscillations in 4 s i.e.

time period is

The time period of a pendulum is given by

where L=length of the pendulum

g=acceleration due to gravity

So, we can write the ratio of the time period of two pendulums as

i.e. 4 times the gravity of the earth

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