Two different balls resting on a high shelf are pushed by a spring. How will their mass affect their range of flight?

Set and fix the masses of the two balls, and measure their range of flight. Compare the ratio of the masses to the ratio of the distances, and verify that the following always holds:                     M1 : M2 = l2 : l1

Initial Values of Parameters Mass of left ball (m) 4 kg Mass of right ball (M) 7 kg