Q.

An astronaut takes a ball of mass m from earth to space. He throws the ball into a circular orbit about earth at an altitude of 318.5 km. From earth's surface to the orbit, the change in total mechanical energy of the ball is xGMem21Re. The value of x is (take Re= 6370 km):                          [2024]

1 11  
2 9  
3 12  
4 10  

Ans.

(1) 

        h=318.5(Re20)

        T·Ei=-GMemRe

        T·Ef=-GMem2(Re+h)=-GMem2(Re+Re20)

        Change in total mechanical energy = TEf-TEi

         =GMemRe[1-1021]=11GMem21Ren