If he throws the ball (with mass 0.07 kg) with a speed of 28 m/s and there is no air resistance, how high does the ball go?

Since the problem did not state any angle of inclination, I assume that the motion was an object thrown up. There are already equation for motions of this kind that are all based from Newton's Laws of Motion. In this case, the maximum height reached by an object, denotes as Hmax, is

Hmax = v₀²/2g, where g is the acceleration due to gravity which is equal to 9.81 m/s and v₀ is the initial velocity of the ball. Substituting the values,

Hmax = (28m/s)²/2(9.81m/s)
Hmax = 39.96 m

Therefore, the ball thrown up could reach as high up to 39.96 meters.