Construction of our Cannon

Construction of Launcher
The students working on the construction of this cannon are Christina Lilley, Matthew Karas, Travis Koenig, and Calvin Marshall. To start this project off Christina and I started researching for designs we could use to build the launcher. Eventually I found this site http://superfish.orcon.net.nz/megasite/mortar.htm which used Pringle cans, (similar to tennis ball tubes) so we decided to use their design. Now we are going to research what type of gas law is being used here and any way to maximize the distance the ball will travel. (We are also trying to find a way to tilt the cans. We’re thinking of using the metal cap that came with the can to tilt it.) Our backup plan if the aluminum top doesn’t support the cannon is to use one of the tennis ball cans to prop the other one up at an angle. We are having some difficulty with the weight of the cannon and the strength of the materials being used to prop it up.

My group has now cut the bottom off of one of the cans and we are planning to use it to prop up the cannon. However, we are having some trouble fitting the two cans together so we are going to cut the small metal ring off of one can so they will fit. Now we are trying to increase the pressure in the cannon by putting in a baffle. We punched a tiny hole in it and are trying to make it fit snugly in the cannon so that the increased air pressure will blast the tennis ball farther.

We have put the two cans together but we have used both of them. Now we are having a problem angling our cannon to maximize the distance traveled by the tennis ball. We have a bottom of a can, an aluminum top and the plastic top to one can. We have to angle it up at the right point otherwise the cannon will fall forwards and we’re having trouble constructing a base. We figured out a way. We used the bottom of the can and the aluminum top and tilting them against one another we made a base. The cannon also tilts up at the end so we hope that that will help.

We tried a weight test and our cannon fell over. However, we redesigned the base and the cannon now passed our test.

Hypothesis
We believe that our cannon will launch the tennis ball to a distance ranging from 2-6 feet due to the large combustion chamber and angle of the cannon.

Physics of projectile motion
I did some research on the physics of projectile motion. At this site, http://www.fortunecity.com/greenfield/eagles/180/projectile_motion.html I learned that the horizontal motion and the vertical motion of an object have no effect on one another. This means that if an object moves up and down on a bus that is moving at a constant speed, the object’s vertical motion will not be affected. I will continue to move up and down as if the bus was not moving. I also learned how to find the distance an object will travel. It all depends on the angle that the object was projected at and the initial velocity of the object. To find the time the object is in the air we take the Cos of the angle the object was projected at. This is the speed the object is moving at horizontally and it will continue to travel at this speed as long as it remains airborne. Now we must find the vertical velocity of the object. To do this we find the sin of the angle the object was projected. However, we must take into account gravity. Gravity is a force of -9.8 m/s. It is a negative because we are working with velocity and gravity is pulling the object in the opposite direction that it is traveling. So you divide the initial vertical velocity of the object by the force of gravity and multiply by two to find the time the object will remain airborne. Now to find the distance the object traveled you multiply the time the object is in motion by the horizontal velocity of the object.

Effects of the Gas Laws
With this experiment I believe that the gas law being applied here is Combined gas law Law. I believe this because the temperature will increase because there is a combustion reaction taking place. When the combustion reaction takes place in the chamber of the cannon, pressure will build in the chamber and heat, a constant volume. However there is a baffle so the carbon dioxide produced will fill the shaft of the cannon, building pressure behind the Nerf ball in the somewhat smaller chamber. As the carbon dioxide fills the smaller chamber the pressure will decrease in the larger chamber but will increase behind the Nerf ball, creating enough force to shoot it out of the cannon. The pressure, volume, and temperature is changing in this reaction and this is why the Combined Gas Law is applied.