Question
A body is projected vertically upward from the surface of the earth so as to reach a height equal to the radius of the earth. Neglecting resistance due to air, calculate the initial speed which should be imparted to the body.
with kinetic energy equal to half of the minimum value needed to escape it. Find the maximum height to which it rises above the surface of the earth.
Solution
Work done inorder to take the body from the surface of the earth (x-R) to aheight equal to R (x = 2R) is given by, 
