1
Balloon Popper
Tuesday, December 5, 2006
Tommy Townsend, Alaka Hoskins, Justin Dempsey, Jeff McRiffey
Summary:
The object of this task was to build a Rube-Goldberg device. A Rube-Goldberg device is an over-complicated device that performs a simple task. The goal was to create a device for under $20 and make it work. We used a device with several steps to eventually pop a balloon.
Design Process:
We came up with a simple idea to pop a balloon. We first got together to brainstorm, and then to finally build the object. We changed the design radically while we were building it. We had some ideas for things like dominoes and cars, but we decided that it would be easiest to stick with bouncy balls. We scavenged some scrap wood and got to work on the track. We made an incline for the smaller ball to travel down. We had to elevate the whole track so that it could have potential energy going down. It kept falling off, so we had to put up cardboard bumpers. We made a holder for the balloon, and a seesaw to attach the thumbtack.
How It Works:
The first ball, which has a significantly smaller mass compared to the large ball, is started on an incline. It works its way down the track due to potential gravitational energy, and hits the large ball. The small ball has enough kinetic energy to move the ball enough to fall off of the track onto the seesaw. The gravitational energy from the large ball hits the seesaw and causes the other end to rise. The seesaw has a thumbtack attached to the end, and that end is positioned under the inflated balloon. The thumbtack is raised with enough force to pop the balloon and the balloon pops.
Energy Conversions:
Step 1: The first ball starts from rest and changes potential gravitational energy into kinetic energy as it moves down the track. The track is taped so we assume friction to be negligible.
Step 2: The first ball hits the second ball and transfers its kinetic energy. We are going to assume that the collision is perfectly elastic, so the coefficient of restitution is set at 1.
Step 3: The second ball rolls off of the track and converts its potential gravitational energy into kinetic energy by hitting the seesaw. This causes the balloon to be popped by the tack on the other end.
Energy variables: Each velocity is calculated ignoring friction and air resistance. The coefficient of restitution is also assumed to be 1. The masses were calculated with a scale, and the heights were measured with a tape measure.
Materials Used and Estimated Total Cost:
Everything that we used for the main structure was scavenged from scrap wood and materials. We used nails and screws from the
Scavenged Materials:
-Wood$5.00
-Screws$0.50
-Nails$0.50
-Cardboard$1.00
-Tape$2.00
Bought Materials:
-Bouncy balls$1.00
-Balloons$2.00
Estimated Total Cost: $12
Conclusions:
Our biggest problem was getting the balloon to pop, but we figured out what was causing the problem. The balloon was too thick, so we had to blow it up more. Also, the balloon was moving too much, so we taped it to not move. We also tried many different things (nails, screws, etc.) to see which popped the balloon most efficiently. We ended up going with the thumbtack, because it was most sharp and did the job most consistently.
References:
We used the resources given to us on the EF 151 website for inspiration.