Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : A pendulum clock when taken to Mount Everest becomes fast.
Reason R : The value of g (acceleration due to gravity) is less at Mount Everest than its value on the surface of earth.
In the light of the above statements, choose the most appropriate answer from the options given below

Solution

Physics sir · 4 steps

Less g means a longer period, so each tick takes longer and the clock falls behind, not ahead.

1. Check R first. On Everest you are farther from the centre of the earth, and g = GM/(R+h)² falls as h grows. So g is smaller there, and R is correct.

   T = 2π√(l/g)

2. Effect on period. With l fixed, a smaller g gives a larger T. Each swing takes longer than the one second the clock was set for.
3. Fast or slow. The clock counts swings, so fewer swings fit into a real hour. It shows less time than has actually passed: it loses time and becomes slow. So A is not correct.
4. So. A is wrong and R is right, which is option (d).

The idea to keep. A pendulum clock is fast when its period is short and slow when its period is long. Whatever lowers g (height, depth, the moon) makes it slow.

Answer from the NTA final answer key. Solution by PrepWiser.