Tennis Ball Launcher
Posted 1229478027|%A %B %d, %Y|agohover
For math class, we had to build a tennis ball launcher that can launch a tennis ball 20 meters into a target the size of the ball itself. "Impossible!" my first thought was.

The first thing my group and I had to do was find the possible factors and define the problem. We had to take into account the amount of power, angle of the machine, height, wind, gravity, friction, air resistance, temperature, air pressure, earth elongation, magnetic polarization of the sun, cosmic remnants of supernovas, time warp due to rotational velocity, etc. Anyway, our main problem was simply harnessing enough power to propel the ball into the target 20 meters away without using explosives, pressurized systems, or motors.

Our first thought was to use a rat trap. We figured a rat trap would give enough power. How wrong we were, it only went 4 meters. Our final alternative was to use bungee cords. So, my dad and I went to Lowes in order to get some materials. We wanted to make a launcher rather than a catapult, so we needed PVC. Unfortunately, there wasn't any PVC that perfectly fit the ball. All this misfortune, and when was it due? In eight days!

We ended up finding something called a Beer Chick which is used to cook beer and chicken. For some odd reason, the ball fit perfectly, so it was a go. On Friday, 4 days before the due date, we had to assemble a machine out of a wooden dowel, one wooden plank, a 2 foot long tube with a two inch PVC joint on the end, two bungee cords, screws, duct tape, a Pepsi bottle, and the Beer Chick. After some intelligent thinking and "spectacular" building skills, we finally created a launcher.

The launcher (which we named the Combustible Kunai) was an upright plank with the tube at a 45o angle. On the PVC joint, we put the Beer Chick, which is where the tennis ball goes. We stuck the dowel into the tube so it can slide up and down. At the end without the Beer Chick, we attached the Pepsi bottle to act as our stopper and hook. Since the Beer Chick had two loops, we hooked the bungees on those and brought them to the Pepsi bottle. So, when you pull the dowel back, the bungees stretch because they are latched to the Pepsi bottle on the dowel and the Beer Chick. When you let go, the dowel is propelled up the shaft into the Beer Chick (where the ball is) to hit the ball.

Over the weekend, we modified it so that it had a base, was more sturdy, and replaced the Pepsi bottle with a T-joint. Before we knew it, the project was due.

Well, today was the launching day for the project. What surprised me was that out of the seven groups, ours was the only one that was even capable of launching 20 meters. We first did a distance check to see how much power our machine had. We got 83 feet, almost double second place. Next was the accuracy check to see how close to the target we could hit. We got four shots and we hit 2.5 feet from the target. Overall, our machine was a total success.

Now it remains to be seen what becomes of our grade. Since none of the other groups came close, will there be a grade curve? I hope so. I am finally relieved that one of the major projects is at last finished.


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