Two pendulums begins to swing simultaneously. The first pendulum makes $11$ full oscillations when the other makes $9$. The ratio of length of the two pendulums is

A simple pendulum of length $ l$ has a brass bob attached at its lower end. Its period is $T$. If a steel bob of same size, having density $ x$ times that of brass, replaces the brass bob and its length is changed so that period becomes $2T$, then new length is

Is the oscillation of a simple pendulum at the centre of the earth be possible ?

If two persons sitting on a swing instead of one, why the periodic time does not changed ?

The period of a simple pendulum measured inside a stationary lift is found to be $T$. If the lift starts accelerating upwards with acceleration of $g/3,$ then the time period of the pendulum is

A simple pendulum with length  $L$ and mass $m$ of the bob is vibrating with an amplitude $A$. The maximum tension in the string is