Final Team Project

“The contraption that will open your cellular device”

Alan Grissom

Amanda Lee

Robby Hoelke

Krista Wesselkamper

Engineering Fundamentals 151

April 26, 2006

Project Description

A device in which, through a series of energy conversions, allows someone to answer their cell phone.

Mechanical components are as follows:

  1. A funnel fills a bottle with water.
  2. The weight of the water pulls down the bottle, which in turn pulls down a string that is attached to the bottle.
  3. Force from the string that is on a pulley causes the string to lift a side of a board and produce an incline.
  4. The produced incline of the board causes a ball on the board to roll down the incline.
  5. The ball rolls down a path and lands on a mousetrap.
  6. The weight of the ball causes the mousetrap to go off.
  7. A string is tied onto the mousetrap that is attached to the top portion of the cell phone.
  8. The force of the mousetrap spring’s force on the mousetrap bar pulls the string.
  9. The tension force of the string causes the cell phone to open.

Design Process

  1. First, a final outcome was chosen. Several ideas were discussed, such as, opening a soda can, and releasing a balloon. Finally, an agreement was reached on opening a cell phone.
  1. Next, there was discussion of possible components of the device that would achieve the final outcome. Consideration was given to the project guidelines of having at least three energy conversions and not exceeding the $25 budget.
  1. A sketch was then made to aid with construction.
  1. Throughout construction, adjustments were made in order to fine tune the device. These included:
  2. Cut the tube of the funnel.
  3. Get a smaller pulley.
  4. Get a bottle instead of a can because the can was too small.
  5. Get additional weights to hold the mousetrap down because the force of the trap going off was sending it flying.
  6. Added the pendulum apparatus to decrease the velocity of the final golf ball.

Analysis of Energy Conversions

According to the Law of Conservation of Energy, if all the collisions were perfectly elastic and there were no energy losses due to friction, heat or air resistance throughout this device, then the initial potential energy of the weighted bottle at the start of the system should equal the final kinetic energy of the phone being opened at the end. However, this was not the case. Therefore, the final energy should be expected to be less than the initial. The difference between the two values is the energy lost.

The energy conversions of this devise are as follows:

  1. The KE of the bottle moving downward equals the KE of the board moving upward.
  2. The KE of the board moving causes the ball’s velocity to start rolling down the ramp, plus the Eloss of the friction of the ball rolling.
  3. The force of the ball’s weight equals the necessary force ale to set off the mouse trap.
  4. The trigger of the trap releases the force in the compressed spring.
  5. The string attached to the spring of the trap exerts the same force of the released spring.
  6. The force on the string equals the amount of energy required to flip open the cellular device.
  7. The Eloss obtained through the device does not compare to the amount of the excess amount of energy produced by the flipping of the phone to be opened.

Calculations:

In order to determine the energy efficiency of our device, ideally, calculations for each of the individual energy conversions are needed in order to evaluate exactly where and how much lost or excess energy was produced along the way. In this case, several estimations would have to have been made for the spring constants, the coefficients of restitution and the coefficients static and kinetic friction. So instead, our calculations reflect measurements of the can in its initial weighted state, as well as, the measurements of the fifth golf ball from its initial state of rest to right before it hits the bottom of the hole.

  1. Initial PE (can) = mgh = (.380kg)(9.81m/s^2)(.17m)=.634J
  2. The KE of the board moving upward= .634J
  3. The velocity of the ball is 1.826 m/s, due to the PE of the ball before it moves is equal to the KE of the ball after it moves. Mgh=1/2mv^2
  4. The weight of the ball equals the amount of energy to release the trap. .211 kg
  5. The amount of energy in the mousetrap equals and exceeds the amount of energy required to open the cellular device.

Assumptions:

  1. Friction and air resistance where neglected. The efficiency would therefore be slightly lower.
  2. Exactly the same amount of water was added each time varying the initial mass of the can.
  3. Human error in taking the measurements.

Bill of Materials

Funnel$1.29

Wood 7.91

Tubing 2.44

Mousetrap 1.50

Screws & nails 1.20

Duct tape .25

String .03

Total $14.44

Summary

The device worked well in achieving our anticipated outcome. However, it could have been made to be more energy efficient by using a different combination of materials to perform the same functions. The device was not successful the first time or even the first ten times, but when we worked together and tried again and again, we came out on top.

The project as a whole was a success. Each team member equally contributed and were open-minded to each other’s ideas. We were able to apply many of the concepts we learned this semester and in addition were able to demonstrate teamwork, innovation, technical skills and communication skills.

Individual Contributions

Each team member was in charge of one major aspect of the project but everyone contributed to all areas and all decisions were made as a group.

  1. Amanda Lee: PowerPoint, pictures and uploading of files
  2. Robby Hoelke: Construction and fine tuning of device, Materials
  3. Alan Grissom: Report and Construction, Idea
  4. Krista Wesselkamper: Revisions, Final Preparations
  5. All: Presentation and demonstration