The escape velocity of a body from Earth's surface is`v_(e )`. What will be the escape velocity of the same body from a height equal to 7R from Earth's surface.

Explanation

`v_(e) prop 1/(sqrt(r))` where r is the position of body from the surface .
` (v_(e))/(v.) = sqrt((r.)/r ) = sqrt((R+7R)/R ) = sqrt((8R)/R ) = sqrt(8) = 2sqrt(2)`
` :. v. = (v_(e))/(2sqrt(2))`