A ROCKET IS FIRED VERTICALLY FROM THE SURFACE OF MARS WITH A SPEED OF 2km/s IF 20%OF IT'S INITIAL ENERGY IS LOST DUE TO MARTIAN  ATMOSPHERIC RESISTANCE,HOW FAR WILL THE ROCKET GO FROM THE SURFACE OF MARS BEFORE RETURNING TO IT?

 

I HAVE TRIED THIS QUESTION.PLEASE EXPLAIN WHAT'S WRONG IN THIS?

80/100(1/2m*2000*2000+GMm/r)=GMm/(r+h)

where M=mass of mars

r=radius of mars

h=height upto which the rocket would go