example07_annotated_en.pdf - Investigation 7(annotated...

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Physics teacher support material 1Investigation 7 (annotated)Exploring the relationship between the pressure of the ball and coefficient of restitution. When I started thinking about possible investigations I knew I wanted to create a lab that was related to sports. After a number of ideas, I thought that changing the pressure of the ball would be a good independent variable and the rebound height of the dropped ball would be a good dependent variable. This was very interesting to me because I had just started basketball season and it’s always a struggle finding a good ball to use at practice. Some balls are too bouncy and others are under inflated. My sister and I are also very particular about our soccer balls. When the ball is over inflated it’s harder to control, and when it is under inflated the trajectory of the ball is altered. I finalized my investigation to deal with the rebound height of different size soccer balls when they rebound off of different materials with different pressures, and that I should test the rebound height of the ball when it is under inflated and over inflated. After some research I discovered that the ideal pressure for a size 5 soccer ball is 6-8 Lbs. FIFA measures the pressure of the ball in bars but for this experiment I will use lbs.In physics we usually talk about air pressure in atmospheres, but for soccer balls the pressure is usually measured in Lbs. or bar. Coefficient of RestitutionThe coefficient of restitution is a mathematical way of showing the elasticity of a collision. It can be used when two moving objects collide or when a moving object hits a stationary object. In my investigation a moving object (a soccer ball) will collide with the ground. There are many formulas to calculate the coefficient of restitution depending on the data that you are given, but the one listed below specifically deals with the height of ball bounces. If the collision is perfectly elastic, meaning that no energy is transferred, the coefficient of restitution will be 1. Collisions are not perfectly elastic because energy is lost on collision. If the coefficient of restitution is 0, the collision is completely inelastic and all energy is transferred from the ball to the ground, friction, sound, heat and other forms of energy loss. This would mean that when the ball drops, it doesn’t bounce back. Energy Transfer in this experimentThe soccer ball is first raised up to a specific height. In this action energy is being transferred from the person to the ball. When the ball is resting at its maximum height all of its energy is gravitational potential. As the ball is released, gravity accelerates it towards the EXand CThe title does not describe the entire investigation. The student lacks focus.

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