Ask your students to research atmospheric air pressure. They should find out that air has weight. The weight of the air pressing down on the surface of the ground causes air pressure. At sea level, air pressure is greater than above sea level; this is because the column of air above the ground at sea level is longer than the column of air above sea level.
Illustrate the concept of air pressure with a simple demonstration. Use a glass jar with a mouth that is about 2 inches in diameter. With a match, light a small piece of paper and quickly drop it into the jar. Immediately place a peeled, boiled egg on the jar's opening, pointed side down. The egg will be forced into the bottle.
The fire uses up the oxygen in the bottle, thereby reducing the air pressure that is inside. This imbalance forces the egg into the bottle and balance is restored.
Direct the students to research how pressure and a ball's bounce is related. They should determine that, before the ball is inflated, the interior of the ball has no outward pressure. Instead, the atmospheric air pressure pushes inward on the ball, keeping it collapsed. As air is pumped into a ball, the air pressure is increased on the inside of the ball, overcoming the air pressure from without; thus, the ball is inflated.
Dropping a ball causes it to gain kinetic energy, energy of motion. As the ball hits the ground, this energy of motion is transferred to the ball's covering and into the air molecules in the ball. On contact, the exterior of the ball bends inward, thereby compressing the air molecules and storing the transferred energy. Momentarily the ball stops. The ball then bounces back as the ball and air resume their initial shape and position.
In order to study the effects of pressure on a bouncing ball, your student will inflate a ball to varying pressures, drop it from a specified height, and measure how high the ball bounces.
For example, tell her to tape a meter stick to the wall, to inflate the ball to 2 psi and to drop it from a height of 1 meter. She will determine the height of the bounce by measuring the maximum height reached by the lowest part of the ball. Repeat a minimum of 10 times, recording the data each time on a data table.
Instruct her to repeat this procedure after consecutively inflating the ball to 4 psi, 6 psi, etc. until she reaches the maximum amount of pressure allowed by the manufacturer.
It is important that she follow up her data collection by making a bar graph of her results. Using a graph will help her visualize her results so that the next step, formulating her conclusion, is simplified.
When implementing this procedure, be consistent. Always drop the ball from the same height and in the same location. This prevents varying responses due to differences in flooring, in temperature, and kinetic energy. Use the same ball each time to prevent variations in the material from affecting the results. When measuring the height of the ball's bounce, always endeavor to keep your eye as level with the bottom of the ball as possible. If you look from too far above or below, your measurements won't be accurate.