This discovery also confirms my hypothesis that air pressure in a volleyball affects its rebound height. In “The Physics of Rebound Height” section of my paper, Isaid the rebound height of a deflated volleyball should be less than the rebound height when it is inflated. The graph visibly proves my prediction was correct because as psi increased, the rebound height of the ball always increased as well. This trend is due to energy loss from air resistance and the sound and heat given off during the ball’s collisions with the ground. Also, thehigher collision times with a deflated volleyball than an inflated one causes a lower rebound height for balls with lower internal air pressures. As previously stated, in my trials the volleyballdid not return to its original height when it was bounced because it lost energy when it hit the ground. The collision time for the volleyball-gym floor collision affected the rebound height as well because it had an inverse relationship with the force acting on the volleyball during the collision since impulse is constant for constant masses. Logically, a volleyball with less air pressure has less air molecules. This difference in molecule quantity causes a deflated volleyballto deform more when it hits the ground and take longer to return to its original shape after impact. ConclusionIn this laboratory investigation, I measured and graphed the rebound heights of a volleyball dropped from 50.00 inches in the air at various pressures. This experiment confirmed the direct relationship between the pressure of a volleyball and the rebound height. I calculated the relationship to be 2.9 cm/psi ± 0.8 cm/psi. Although I could not find any data on the relationship between cm of rebound height and internal air pressure in psi, the results of this investigation conform to those of other investigations about the rebound height of balls on gym floors because the results show that rebound height increases as the pressure increases. My graphshows me that if I want a volleyball to bounce up to my waist (which is about 38.00 inches abovethe ground), when dropped from my eye level (which is about 50.00 inches in the air), I would have to apply a force to the ball in order to increase the rebound height of the ball. This is true because the maximum rebound height of the ball at any pressure is about 83.75 cm or 32.97 inches at 9 psi. This investigation also confirmed that rebound height of a volleyball has less magnitude than initial height. I can conclude that this phenomenon is caused by the energy loss from air resistance and the sound and heat that are given off during the collision with the ground. Therefore, elastic potential energy of a deflated ball must be less than the elastic potential energy
of an inflated ball. Due to this fact, the spring constant of an inflated ball must be significantly larger than that of a deflated ball. Elastic potential energy is equal to the product of the spring constant of a spring or a ball and the distance the ball is deformed squared.