A5.0-n projectile leaves the ground with a kinetic energy of 220 j. at the highest point in its trajectory, its kinetic energy is 120 j. to what vertical height, relative to its launch point, did it rise if there was no air resistance

First, we get the difference between the kinetic energies such that,
             difference = (220J - 120J)
             difference = 100 J
The difference in kinetic energy is the equivalent of the potential energy which is calculated through the equation,
              PE = mgh
To calculate for the height, we derive the equation in a form,
           h = PE/mg
The product of the mass and acceleration due to gravity is the weight. 
                   h = (100 J) / (5 N)
                   h = 20 m

Hence, the answer is 20 m.