Action, Reaction what's your Retraction?
Martin Drone
David Jacobs
Logan Johnson
Robert Harshman
Overview
Our objectives were to create a project that had at least three energy transfers, and
yet performed a simple task at the end of the device's processes. Even though we had to
do all this, we had a limit of 20 dollars to spend creating this project. Our project
consisted of many more than three energy transfers. We had various gravitational
potential energy to kinetic energy transfers, many collisions, and a spring force too. At
the end of the project, our device retracts a tape measure.
Design Process
To start of the project, the group first met and talked about the possible scenarios
we could use. The group brought up some good ideas; we decided to use a marble to go
through a series of energy transfer and collides with a golf ball. The golf ball then rolls
down an incline and collides with a downward facing sprung umbrella which forces a
lever to open a coke. When we met again we took a trip to the local home depot. There
were realized that the golf ball was not heavy enough to trip the button on the sprung
umbrella. We then decided to lose the golf ball and the umbrella and replaced them with
a mouse trap. Before leaving the home depot the group purchased a peg board which
would server as a good support for the plastic ramps that the marble runs along. From the
home depot we headed to Estabrook were we constructed the project. Earlier the idea to
play the ending sound of the Japanese devices on Youtube.com came up, so the group
found a CD player, fastened a rubber mallet to the mouse trap, and recorded the sound
from the Japanese devices. This, sadly, did not work. The mouse trap mallet was not
strong enough to trip the button on the CD player. It was here that we decided to contract
a retractable tape measure. The project came together nicely working 100% of the time
Device
Our device is basically a series of ramps with
collisions in between every so often. First it starts
off with a collision between a golf ball and a
marble(fig 1.1). The golf ball is tied to a string
with acts a pendulum, and when released at the
right height, the golf ball swings down and collides
with the marble causing it to proceed forward
where it falls from ramp 1(see fig 1.2) down onto
ramp 2. Then after rolling down ramp 2 the
marble falls onto ramp 3 where it collides into marble
2(fig 2.2), creating a perfectly elastic collision( see
assumptions in data section). Marble 2 continues to
proceed across ramp 3 and rolls onto ramp 4, where it
proceeds to fall onto ramp 5 and collides with a block,
creating another perfectly elastic collision. Then this
marble proceeds down ramp 5 where it rolls onto a
mouse trap, that has a rubber mallet like object
attached to it. This rubber mallet like object hits a
tape measure button causing the tape measure to
retract.
Calculations
Vgolfball :mgh=.5mv2
Vgolfball=√(2)(9.81)(0.00635)
Vgolfball=0.35297 m/s
Vmarble: m1v1=(m1+m2)V1'
(0.045)(0.35297)=(0.045+0.0035)V1'
V1'=0.3275m/s
Ramp 1 to Ramp 2
.5mv2+mgh=.5mv'2
√2(.5(0.3275)2+(9.81)(0.00889))=V'
V'=0.5307 m/s
Collision From marble 1 to marble 2
V=0.5307 m/s
Ramp 3
mgh=.5mv2
√2(9.81)(0.0127)=V'
V'=0.4992 m/s
Ramp 4
.5mv2+mgh=.5mv'2
√2((.5)(0.4992)2+(9.81)(0.00889)=V'
V'=0.5468 m/s
Assumptions
1) Friction is negligible
2) Collision between golf ball and marble is perfectly inelastic
3) Collisions between marble and marble and marble and wall are perfectly elastic
Estimated Bill of Materials
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peg board
plastic ramps
zip ties
screws
cull lumber
sticky tape
golf ball
string
duct tape
$4.00
$10.00
$0.25
$0.25
$1.51
$0.75
$0.50
$0.01
$0.02
(items not factored into cost)
 jenga block
$0.05
 mousetrap
$0.25
 tape measure
$5.00
 rubber band (mallet) $0.02
 dowel (mallet)
$0.01
Total Cost Estimate: $17.29
Conclusion
We definitely learned a lot about team work. We had to work together to
successfully make this project work. We utilized the ability to come up with a variety of
ideas and then put them all into one design. We also used our knowledge of energy
transfers and the skills we had learned over the semester to apply to this project to do it
completely.
References
http://video.google.com/videoplay?docid=-9133671200734505806&q=goldberg&hl=en
Other than this all ideas came up from just brainstorming.