If the length of a second's pendulum is decreased by $2\%$,how many seconds will it lose per day?

$A$ pendulum has a time period $T$ in air. When it is made to oscillate in water,its time period is $\sqrt{2} T$. Then the relative density of the material of the bob of the pendulum is (neglect damping).

$A$ disc of mass $m$ and radius $R$ is attached to the ceiling with the help of two ropes of length $l$. Find the time period of small oscillations of the disc in the plane of the disc.

$A$ pendulum clock is set to give correct time at sea level. This clock is moved to a hill station at an altitude of $2500 \ m$ above sea level. In order to keep correct time at the hill station,the length of the pendulum:

The ratio of the period of oscillation of a conical pendulum to that of a simple pendulum is: (Assume the strings are of the same length in both cases and $\theta$ is the angle made by the string with the vertical in the case of the conical pendulum.)

When a pendulum clock is running fast,what should be done to adjust it to the true time?