Q.

Escape velocity of a body from earth is 11.2 km/s. If the radius of a planet be one-third the radius of earth and mass be one-sixth that of earth, the escape velocity from the planet is                        [2024]

1 11.2 km/s  
2 8.4 km/s  
3 4.2 km/s  
4 7.9 km/s  

Ans.

(4) 

       RP=RE3, MP=ME6

        Ve=2GMR for earth

         Ve'=2G(M/6)(R/3)=GMR for planet

        2Ve'=Ve

         Ve'=Ve2=11.22=(11.2)×0.7 km/sec

         Ve'=7.84 km/sec7.9km/sec