Question

A bob of a simple pendulum oscillates with an amplitude of 4 cm
and time period 1 s. Find (i) length of the pendulum and (ii) velocity
of the bob in the mean position.

Answer 1

There is a simple formula to solve these questions :-
$T=2 \pi \sqrt{ \frac{L}{g} }$

Where T= Time Period in seconds
L= Length of the Pendulum in meters
g= Value of acceleration due to gravity in m/s^2.
So, putting the values respectively in the answer, we get :-
1 = 2 pi root [L/19.8] = 0.9929 meters ~ 1 meter. 

I don't really know of velocity, but it can be related with mgh = 1/2 mv^2 
Well.. try it :-)