Question

A body is projected from the surface of the earth with thrice the escape velocity `(V_(e))` from the surface of the earth. What will be its velocity, when it will escape the gravitational pull?
A. `2sqrt(2)V_(e)`
B. `2V_(e)`
C. `(V_(e))/(2)`
D. `4V_(e)`

Answer 1

Correct Answer - A
`(1)/(2)mV_(0)^(2)=(1)/(2)mV^(2)-(1)/(2)mV_(e)^(2)`
`therefore V_(0)^(2)=(3V_(e))^(2)-V_(e)^(2)`
`therefore V_(0)=sqrt(9V_(e)^(2)-V_(e)^(2))=sqrt(8V_(e)^(2))=2sqrt(2)V_(e)`