Aprojectile of mass m is fired straight upward from the surface of an airless planet of radius r and mass m with an initial speed equal to the escape speed vesc (meaning the projectile will just barely escape the planet's gravity -- it will asymptotically approach infinite distance and zero speed.) what is the correct expression for the projectile's kinetic energy when it is a distance 9r from the planet's center (8r from the surface). ignore the gravity of the sun and other astronomical bodies. ke (at r = 9r) is: a. gmm/9rb. gmm/8rc. 1/2mvesc^2d. -gmm/8re. none of these