A pendulum clock is set to give correct time at the sea level. The clock is moved to a hill station at an altitude ‘h’ above sea level. In order to keep correct time on the hill station which one of the following adjustments is required?

The time period (T) of a simple pendulum is governed by the formula T = 2π√(L/g), where L is the length and g is the acceleration due to gravity [t1, t8]. As a clock is moved from sea level to a hill station at altitude 'h', the value of 'g' decreases because gravitational acceleration is inversely proportional to the square of the distance from the Earth's center [t2, t4]. According to the formula, a decrease in 'g' leads to an increase in the time period 'T', causing the clock to swing more slowly and lose time [t1, t2]. To maintain the correct time (keeping 'T' constant), the length 'L' must be reduced to compensate for the lower 'g' [t1, t6]. The mass of the pendulum bob does not affect the time period, making mass adjustments irrelevant [c1, t1].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > THINK LIKE A SCIENTIST! > p. 110