Light-Switch Hitter
Allison Bainbridge
Adam Elliott
Chris Lezu
Overview
A spring hits a ball and knocks it down a tube. The ball falls into a cup on the end of a see-saw. The other end of the see-saw hits a light-switch, turning it on.
Description of Design Process and Device
Our design started out with a ball rolling down a ramp to flip a switch. After a lot of thought, we decided to use a tube and a see-saw. We went to Home Depot and bought wood, PVC pipe, screws, a hinge, a light-switch and a light-switch cover. We started cutting the wood and drilling holes. Then we started assembling our device. We started with attaching the supports for the pipe to the wood. First, we attached the pipe to the supports with electrical wire. Then we attached the see-saw to a wedge with a hinge. We attached the light-switch to a block of wood and put the faceplate on the switch. We screwed the block of wood to the end of the board. Then we made the platform the ball was to start on. After a few trials, we decided that we needed a force acting on the ball. We tossed around a few ideas including dominos and a spring. We finally decided on a spring and attached it to the platform. Instead of pulling the ball and the spring back together, we decided we needed something to hold the spring back until we were ready to start our device. We cut a piece of Frisbee and used it and two nails to hold back the spring. The last thing we did was try to attach the see-saw to the base. The first time we tried to attach it, the wedge split and we had to take it off and start over with a new wedge. After we ran our device a few times, we realized that the ball wouldn’t roll straight off of the platform. We decided to put two more nails on the edge of the platform and run wire between them to hold the ball on the platform.
Energy Conversions
We start with spring potential and gravitational potential energy. When the spring is let go, that spring potential energy is converted to kinetic energy. Then the kinetic plus the gravitational energy converts to just kinetic energy as it rolls down the tube. There is a momentum conversion when it hits the cup and it also loses some kinetic energy and gains some potential energy. There is a conservation of momentum when the see-saw flips. Then the kinetic and gravitational energy of the cup and ball converts to gravitational energy and the amount of energy lost to the light-switch.
Bill of Materials
Wood:$3.57
PVC Pipe:$2.69
Screws:$4.11
PVC Cap:$1.20
PVC 45° coupling:$.87
Hinge:$2.09
Light-Switch:$.59
Light-Switch Cover:$.44
Spring:$2.13
Electrical Wire:$1.31
Total: $19.00
Basic Calculations
PE=KE
mv1+mv2=(m1+m2)v’
F=Kx
Assumptions
Calculations are done assuming no loss of energy until the final step, the transfer of energy to the switch.
We also assumed a perfectly inelastic collision when the ball hits the cup.
Conclusions
Our Final project was successful. We only needed two trial designs before we decided on the finished project. Our first design seemed too simple with no force acting on the ball. Our second design was not successful because of the ball rolling the wrong way off of the platform. If we had started sooner on our design, we would have been able to take our time and have a more elaborate machine.
References
We used Google to look up the mass of a golf ball.
Final Calculations: