Q.

A simple pendulum oscillating in air has a period of 3 s. If it is completely immersed in non-viscous liquid, having density (14)th of the material of the bob, the new period will be           [2023]
 

1 23 s  
2 23 s  
3 2 s  
4 32 s  

Ans.

(3)

For simple pendulum, T=2πLgeff

According to the question, geff=g(1-ρlρ0)=g(1-14)=34g

So, T'T=2πL3g/42πLgT'=23

As, T=3 s   so   T'=23×3=2s