To solve this problem it is necessary to apply the concept of period in a pendulum. Its definition is framed in the equation
[tex]T= 2\pi \sqrt{\frac{l}{g}}[/tex]
Where,
l = Length
g = Gravity
As you can see, the Period is dependent on both the gravitational acceleration and the length of the string. The period does not depend on mass. Therefore the period must remain the same at 2 seconds.
