# Project Help - Mousetrap catapault to launch cut tennis ball

1. Apr 9, 2016

### Claire Augustus

1. The problem statement, all variables and given/known data

"Take a tennis ball and cut it into 2 equal halves. Take one of them and cut it again equally. You now have 1 half tennis ball and 2 quarter tennis balls. Glue the 2 quarters to the half, one to its outside (convex) and one to its inside (concave). Design, build and test a device that “shoots” this glued piece into a “basket”. The basket is a trash bin, which is about 15" tall and has a circular opening with a diameter of about 12". It stands on the floor.

The device will be powered only by a simple torsional spring operated mouse (not rat) trap. The device will also rest on the floor. At any time through the process, the top reach of the device may not be higher than 15" above the floor. The goal of the device is to shoot the glued ball into the air so that it will successfully drop into the basket. The minimum horizontal distance between the ball, while in the device, and the front of the bin opening is 1m. Also, the ball has to fly over a 24" high obstacle which stands between the device and the bin.

On the due date, Thursday, 14 April, at 2:30 p.m., your team has to submit a written report, showing the device, explaining how it works and providing data about its tested performance. Then each team will demonstrate the working device in class. Each team will get 2 chances. The better result will count."

2. Relevant equations
Many.

3. The attempt at a solution
What we have tried thus far is to attach a small plastic beach shovel to the mouse trap bar (removing all of the other parts). The cut up ball was placed into the shovel and launched at a few different angles. The projectile does not get high or far enough, though, so this obviously doesn't work.

Any suggestions are very appreciated.

Edit: I just want to note that I am able to launch small projectiles far and high enough. The projectile is just too heavy for this, though.

2. Apr 10, 2016

### Simon Bridge

There is not enough detail - the height you can launch the projectile depends on the strength of the spring, the mass of the projectile, and any losses.
You could investigate to find out how much energy the spring stores and use E=mgh to find the maximum height you can theoretically launch to.
You should also investigate where the energy goes ... does the trap bounce or jump for example?
Possibly the plastic shovel is taking too much away - use a lighter scoop.