A satellite is moving in an orbit with half the speed required to escape the earth's field. What is the height of the satellite?

Options

A. 64 km
B. 640 km
C. 6400 km
D. none of the above.

Answer

C

Explanation

`v_(0)=(1)/(2)v_(e ) rArr sqrt((GM)/(R+h))=(1)/(2) sqrt((2GM)/(R ))`
`therefore (GM)/(R+h)=(1)/(4)*(2GM)/(R ) rArr 2R=R+h rArr h=R`
Thus correct choice is (c ).