Question

An object is released from rest. The time it takes to fall through a distance h and the speed of the object as it falls through this distance are measured with a pendulum clock. The entire apparatus is taken on the moon and the experiment is repeated. Then?

• A. The measured times are same
• B. The measured speeds are same
• C. The actual times in the fall are equal
• D. The actual speeds are equal

Answer 1

Answer: (A), (B)

The correct options are
A

The measured times are same

B

The measured speeds are same

On Earth

u = 0

a = -g

s = -H

H = g t${}^2$

(Time taken by pendulum for one complete round)

And we have pendulum to measure the time taken by ball to fall. So how many oscillations does the pendulum do during the timewhen the ball is falling. Let that be n We measure time based on the number of oscillations that the pendulum does

here the number of oscillation is not dependent on g so no matter where you carry the experiment. You will always measure the same time of fall of the object by the pendulum.

So (a) is correct

speed is rate of change of distance

speed= $\frac{distance}{time}$

and acceleration is rate of change of velocity. Here distance is constant and the time is measured by the pendulum which measures same time everywhere as shown above. So yes the speed measured by using pendulum on moon and earth will be same. Option B is correct.