Apendulum clock depends on the period of a pendulum to keep correct time. suppose a pendulum clock is keeping correct time and then dennis the menace slides the bob of the pendulum downward on the oscillating rod.
does the clock run
(a) slow,
(b) fast, or
(c) correctly?

time period is increased so the clock will become SLOW

Explanation:

As we know that the time period of the simple pendulum is given by the formula

here we know that

L = distance of the pendulum bob from the hinge

g = acceleration due to gravity

now here the bob slide down so that the length of the pendulum is being increased

so time period T of the pendulum is also increased

so here the pendulum will take more time to oscillate or to complete one oscillation

so clock will become SLOW

answer: the answer is a