To what vertical does it rise?

Question

A toy rocket, weighing 10 N, blasts straight up from ground level with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J. To what vertical does it rise?

Answer 1

140 J = PE = mgh (all the KE is gone right at the top)

so, h = 140 J/(1.02kg * 9.8 m/s^2) = 14 meters

-Fred