Question

why pendulum clock generally go faster in winter and slow in summer​

Answer 1

A simple pendulum clock consists of a Bob and metal wire connected to the bob.

The time period of a simple pendulum clock is:- T=2π√l/g

that means that time period is directly proportional to the length of a metal wire of the pendulum

In summer the temperature is high and this causes length of metal wire to increase significantly(as the temperature coefficient of metal wire is high)causes to increase the time period of pendulum and this makes the clock slower whereas in winter the temperature is low sothe metal wire contracts and this causes to decrease the time period of pendulum and makes the pendulum faster

Answer 2

During summer, length of the pendulum increases due to which the time period T increases and pendulum takes more time to complete one oscillation. Thus it slow in summer. During winter length decreases, decreasing the time period. Consequently pendulum gains time and dock becomes fast