�If you want to make something that is airtight, waterproof and/or stretches or bounces, then make it of rubber! The industry as we know it today is something over 150 years old although it was about 100 years before that that the first scientific paper was written on this natural material,� (Loadman). Rubber was believed to be used in early Mesoamerican culture to create shoes, coat fabrics, and create bouncing balls for games. Nowadays, rubber is used in many other materials and products because of its unique characteristics. Take a lacrosse ball for instance, a solid rubber ball with the same shape and size as most other balls, like a tennis ball, and it still bounces significantly higher than those other balls. This is because the force acting on the ball is different compared to other balls. This is because the insides of the rubber ball is made of strands of carbon, think of this like a bowl of spaghetti, where strands are attached at different and random points throughout. When the ball hits the ground the �spaghetti� compresses. With all this compression the force within the ball increases as the downward force on the ball decreases; during all this, also, the ball is using up the energy from within the ball. When the downward force becomes less than the force within the ball the strands return to their original position, causing the ball to push off and spring off the floor, (Brown). Another characteristic of rubber is that temperature can have a drastic effect of the balls bounciness. This is because as the ball gets colder the more energy is lost in the collision with the floor, this is because the colder temperature does not allow the ball to compress like a warmer ball, meaning that more energy is needed to compress and decompress the ball, (Tom).

There are many variables that can be involved in studying bouncy balls and their properties in different stages. In our research we are studying just how much temperature affects a lacrosse ball and its energy loss. A main variable we have to look for in order to calculate change in potential energy is the change in height, or Δh as you will see in our experiment. In order to find the potential energy of the ball after a bounce we will be using the equation,

,where m is the mass of the ball, about 156 grams, g is the gravitational constant, 9.81m/s�, ∆h is the change in height, and Ep is the change in potential energy of the ball after the bounce. In our experiment our independent variable will be the temperature of the ball while the dependent variable is change in height and energy. Our control group will be lacrosse balls at room temperature.

If a rubber ball is heated, then it will retain more potential energy after the first bounce because it uses less force and kinetic energy to compress and bounce back up.

This experiment requires a very simple set up and doesn't require a lot of material gathering. For this experiment you will need to gather the following: Ice, salt, a freezer, access to water, water heating apparatus (stove top), infrared thermometer, a camera, bowls, a scale, and 7 lacrosse balls. Once you have gathered all the necessary equipment

you will need to weigh one of the lacrosse balls to get the approximate mass of the balls, don't worry about measuring the weight after each trial, the temperature should have no effect of the mass of the ball. Fill one bowl with ice and about � cup of rock salt, the next bowl with cold tap water and a few hands full of ice, the next bowl will just have cold tap water. On a stovetop have two pots of water heating up, one pot on medium heat and the other on high. After about 5 minutes place one lacrosse ball in each apparatus, making sure the ball is covered by the water or ice. Wait about 10 minutes for each ball in each apparatus, waiting is important because the longer the balls are in each bowl the colder or warmer it will get to the temperature of each apparatus giving better and more accurate results. Fix a meter stick, you could also use a normal stick and mark one meter, into a visible location, like the side of a table, so that you will be able to see the full meter and floor through the lens of a video recorder. For each trial you will start the camera, you will then take a ball from its respective bowl and take the temperature of the ball, you will then hold it above the meter mark then drop the ball, making sure the video recorder sees through the entire drop. You will repeat for each ball for each trial.

After taking all the trials and videos upload them onto your computer and organize them by apparatus and trial. You will then analyze each video using Logger Pro. Using information from the video, like the length of the meter stick, you will then track the ball as it is dropped to when it bounces and reaches the peak of that bounce. Take note of the starting height and the height of the peak of the second bounce. Record all this data in a data table to find change in height and the potential energy of each ball.

Lacrosse balls, Bowls, Infrared thermometer, Heating element (Stovetop), Pots to use on a stovetop, Access to tap water, Freezer, Video recorder, Ice, Rock salt, Weight scale

After running this experiment we found that, as temperature dropped, the ball would bounce lower and lower off the ground. This causes the change in height to be far greater than a ball that was at room temperature or hotter. With a greater change in height the potential energy within the ball was less than a ball that was warmer that bounces higher in the air.

Our hypothesis was, If a rubber ball is heated, then it will retain more potential energy after the first bounce because it uses less force and kinetic energy to compress and bounce back up. Our results support this idea that more energy is held within the ball after it hits the ground when the ball is heated up. We found that change in potential energy exponentially decays as the ball is heated up, meaning that more potential energy is held within the ball in a curve shape as heat is increased.

This could all be due to the speed of the particles within the ball. As it became hotter the particles in the ball speed up and spread out, causing the ball to become softer and have more kinetic energy. Since it was softer it was able to use less force and it compresses more when it hit the ground; therefore, allowing more potential energy to be kept due to ease of compression.

Some of the main errors that could�ve been made were measuring the height and temperature. The height could�ve been slightly off due to human error. We tried to eliminate this by recording the trials with a meter stick in the background, then analyzing the video using Logger Pro to find out the height the ball reached. This is not an exact measurement, but the uncertainty of this was too small to affect the data. Another error was with the temperature. We used an infrared thermometer to get an accurate reading on the temperature of the ball. The thermometer, however, had a uncertainty of 10�, which could have affected our data negatively since the range of uncertainty was so large. Also, in between measuring the temperature and dropping the ball, there was time where the temperature could�ve been slightly changed, but not enough to affect the data in any substantial way. Another error is that we used multiple balls of different colors; these different colors could affect the temperature gauge because the thermometer reflects differently off of different surfaces and colors.

Next time to improve the experiment we could�ve measured the elasticity of the ball. That is, when it bounces off the ground how much of the gets compressed and changes shape due to the force. By measuring this it will help prove our data, and will also make it more accurate. The only thing is it would be extremely hard to record due to how small of a change it is. The only extra material we would need for it would be a recording device that could go frame by frame so that we can actually watch the ball lose it shape and then regain it. Another thing we could do is create an apparatus to drop the ball. For our trials we just had Jon drop the ball and since we used the program, Logger Pro, it didn�t matter where he dropped it from; we were able to calculate the balls starting point and the balls ending point accurately with this program. This would be a very subtle change, but it�s something we could fix. Creating an apparatus to hold each ball then triggering something to have it drop would produce more accurate data.

Related Websites and Cited Sources: .:. Back to top

http://www.bouncing-balls.com/ - An extensive history of the discovery of rubber and how the modern day rubber ball was invented. Useful in giving background information concerning the founding and uses of rubber and its properties.

http://www.york.ac.uk/media/cll/documents/rubberbounce.pdf - A brief description of how the temperature effects the elasticity of a rubber ball from the University of York.

http://van.physics.illinois.edu/qa/listing.php?id=94 - Q&A with on the University of Illinois website concerning the effects of temperature of rubber balls. Useful in giving different perspectives in this theory of how temperature effects rubber balls.

http://www.livestrong.com/article/401050-does-temperature-affect-how-high-a-tennis-ball-will-bounce/ - Describes how temperature affects the density of a tennis ball and gives examples of experiments that can be done to test this theory.

http://technowyvern.wordpress.com/2008/12/22/the-effect-of-temperature-on-how-high-a-rubber-ball-bounces/ - An example experiment in testing how temperature effects the bounce height of a rubber ball.