Q.

If R is the radius of the earth and the acceleration due to gravity on the surface of earth is g=π2m/s2, then the length of the second's pendulum at a height h=2R from the surface of earth will be         [2024]

1 29m  
2 19m  
3 49m  
4 89m  

Ans.

(2)    

         g=GMR2=π2

         g'=GM9R2=g9=π29

        We know, T=2πlg

       Since the time period of second pendulum is 2 sec.

       2=2πl×9π2

      On solving, l=19m