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Rube Goldberg Device

“The Hipster”

December 12, 2009

E1 Group # 4

David Grueser

Chris Anderson

Ethan Wilburn

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Abstract:

The objective of this project is to create a Rube Goldberg device that raises a banner with five physics concepts being utilized. We demonstrate torque, projectile motion, center of mass, linear momentum, and angular momentum. To make the project appealing we use an iPod to play music, chalk in a mouse trap to create a surprise, and a funky color scheme.

Introduction:

Objective: To create a Rube Goldberg device, "accomplishing by extremely complex roundabout means what actually or seemingly could be done simply."( Webster's Third New International Dictionary ), that will raise a banner.

Requirements: to utilize five physics concepts, a set budget of twenty dollars, time limit of two minutes, safe, size limit of .5m by .5m by .8m, raise a banner.

Design Process:

Initially we started thinking backwards. Starting with how we would finish the project with a pulley raising our banner. Second we went back to the five physics concepts we needed to demonstrate. Our process was to complete one concept after the last to ensure cohesiveness. We realized that simple and sound was better.

To begin, we found a piece of plywood to act as our mount for all the devices. We decided to start with a track near the top of the plywood angled downwards giving the marble some momentum. We had three tracks at first and then we decided to take two off and only use one. We then used a tube with a curved shape that shot the marble out of the end. This demonstrated projectile motion as the marble flies in a funnel mounted on the board. The marble would then fall into a small cup displacing the center of mass of a seesaw. The seesaw was balanced with a cup on one end and washers on the other. So when the marble fell into the cup, it lowered that end and raised the other causing it to hit a golf ball. We used golf balls because more force was needed to start the next process. Then the golf ball will roll down a grooved piece of wood and strike another passing on its momentum. The concept of linear momentum is demonstrated here. Another potential process we initially thought of was to have the golf ball hit a rotating piece of wood. The wood would then spin and hit a box car and roll down a track and hit a lever. Ultimately we decide this process was too intricate and too prone to failure. What we now have is the second ball rolling onto a track hitting the lever. Only the second ball rolls down the track because with linear momentum, the initial golf ball’s second velocity is zero. The lever rotates

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showing angular momentum, and sets off a mouse trap that throws out chalk powder and pulls a string. Also with the golf ball rolling down the track, it falls down onto a platform turning on an IPod connected to some speakers. Now the afore-mentioned string being pulled is connected to a piece of wood that acts as a stopper that holds a golf ball in place on an angled ramp; so when the string is pulled and the stopper is gone the golf ball will be free to roll. The golf ball then rolls into a cup with a string attached to two pulleys that raise the flag. Our thoughts now go back to the beginning and the process which initiates our marble. And ultimately we decided a string would pull a lever that would tip the marble on the track.

Device Description:

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Price List:

PVC Pipe – $2.00

Wood - $5.00

Mouse Trap - $1.00

Funnel - $.35

Golf Balls - $.75

Yarn - $1.00

Yard Stick - $2.00

Screws and Washers - $1.00

Marble - $.25

Cup - $1.00

Pulleys - $4.00

Glue - $1.15

Total – $19.50

Analysis:

Projectile Motion -

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Center of Mass – R= (mr+…+m*r*)/(m+…+m*) Linear Momentum – P=mv

Angular Momentum – L = r × p

Torque – Torque and Acceleration Τ= Iα Calculations:

Mgh= (.028kg)(9.81m/s²)(.35m)= .096 Joules

C.O.M = mA/2 = (.053kg)(.006m²) = .000318 kg*m²

C.O.M = ICM + m*r= .000318kg*m² + (.028kg)(.15m)= .0045 kg*m²

Mv1= Mv2 v1=v2 .93 m/s = v2 v2 = .93 m/s

L = r*p= (.93m/s)(.056kg)*(.2m) = .0104 (kg*m²)/s

Torque MT = (1/2)kω² = (.5)(.211 Nm)(34.6 rad/s)² = 126.3 Nm

Assumptions:

Gravity is constant

Friction is negligible

Conclusion:

Success:

Our project over all works effectively in raising the flag and demonstrating five physics concepts.

Learned:

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In this project we learned that less moving equals more accuracy. We also learned that being creative is good, but overcomplicating is bad. Also, it’s easier to concentrate on one step at a time and connect them as a whole as opposed to looking at the whole project at once and trying to get it to work.

Problems:

We had problems initially with the marble falling from the track into the tube to fix it we just had to move the tube closer. We also had a problem with our projectile motion device. The marbles landing would vary in distance and sometimes not make it to the funnel, so we put a safety track in place to make sure it made it to the funnel if it did not get the right velocity.

Alternatives:

We could have done a rocky top theme with orange paint and rocky top music playing.