Rube Goldberg Machine Design Contest Teacher Training

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Rube Goldberg Machine Design Contest Teacher
Training

• Jean Zheng
• Massachusetts Institute of Technology
• Department of Mechanical Engineering
• January 29, 2005

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Topics

• Engineering problem solving process
• Measurement Systems
• Statics and Dynamics
• Energy
• Springs
• Collisions
• Friction
• Formulas

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Engineering Problem Solving Process

• Identify the problem
• Make observations related to the problem
• Propose a root cause for the problem
• Design an experiment to test the hypothesis
• Run dry lab experiment before actual experiment
• Carry out actual experiment
• Analyze data and draw conclusions
• Solve problem, or formulate another cause for the
  problem and repeat steps 4-8 until problem is
  solved

Example My computer mouse has become
lethargic and unresponsive recently. When I
move my mouse, often the cursor on the computer
screen wont move with it.
4
Measurement System

• English commonly used in the US
• 1 mile 1760 yards1 yard 3 feet1 foot 12
  inches

• Metric adopted by the rest of world
• 1 kilometer 1000 meters1 meter 10
  decimeters1 decimeter 10 centimeters1
  centimeter 10 millimeters

Both systems can be used to measure length, area,
volume, time, liquid capacity, velocity,
acceleration, force, mass, weight, etc. Choose
one system and stick to it! (NASA incident)
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Statics and Dynamics

• Statics things that are in equilibriumDynamics
  things that are in motion
• Newtons Laws of Motion
• In the absence of any external forces, an object
  will continue doing what it was doing
• Force is the rate of change of the momentum of an
  object, which is equivalent to the mass of an
  object times its acceleration (Fma)
• If one object exerts a force on another object,
  the second object will exert an equal and
  opposite force back on the first object

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Energy

• Total energy is conserved, but can be
  transferred/converted from one form to another
• Many forms of energy!
• Potential energy energy an object has in its
  current state
• Kinetic energy energy of object in motion
• Many ways of storing energy!
• Many ways of transferring energy!

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Springs

• Forces and energies!
• Displacement is linearly proportional to force
  applied (Fkx)
• Total energy stored 0.5kx2 (potential energy)
• Common uses car shock absorbers, screen door
  pistons, mousetraps

x
F
8
Collisions

• Transfer of energy
• Collisions can be perfectly elastic, elastic, or
  perfectly inelastic
• perfectly elastic mechanical energy conserved
  during the collision, objects do not stick
  together
• elastic mechanical energy not conserved, objects
  stick together for a brief moment
• perfectly inelastic mechanical energy not
  conserved, objects stuck together after collision

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Friction

• Dissipative force
• Opposes direction of motion
• Friction constant different between different
  contact materials and surfaces
• Depends on surface area contacted
• Various forms (heat, sound, etc)
• Design machines with friction in mind!

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Formulas

• Newtons Second Law of Motion
• Conservation of Mechanical Energy
• Potential Energy
• Kinetic Energy
• Spring Force
• Spring Energy
• Momentum (collisions)
• Friction

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Conclusion

• Physics is now your new best friend
• Double-check your calculations
• Planning is everything
• Teamwork is also everything
• Design for manufacturability, accuracy, and
  predictability
• Have fun with the contest!

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Additional Resources

• High school physics books
• Other teachers at your school
• MIT student mentors
• MIT Museum
• www.rube-goldberg.com
• Other online resources
• Teammates!