Rube Goldberg Machine Design ContestJean Zheng, MIT MuseumJanuary 29, 2005 Rube Goldberg Machine Design Contest Teacher Training Jean Zheng Massachusetts

Rube Goldberg Machine Design ContestJean Zheng, MIT Museum January 29, 2005

Rube Goldberg Machine Design

Contest

Teacher Training

Jean ZhengMassachusetts Institute of TechnologyDepartment of Mechanical Engineering

January 29, 2005


Topics

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


Engineering Problem Solving Process

1. Identify the problem2. Make observations related to the problem3. Propose a root cause for the problem4. Design an experiment to test the hypothesis5. Run “dry lab experiment” before actual

experiment6. Carry out actual experiment7. Analyze data and draw conclusions8. Solve problem, or formulate another cause for the

problem and repeat steps 4-8 until problem is solvedExample: “My computer mouse has become ‘lethargic’ and

unresponsive recently. When I move my mouse, often the cursor on the computer screen won’t move with it.”


Measurement System• English – commonly

used in the US• 1 mile = 1760 yards

1 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 millimetersBoth 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)


Statics and Dynamics

• Statics – things that are in equilibriumDynamics – things that are in motion

• Newton’s 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 (F=ma)

– If one object exerts a force on another object, the second object will exert an equal and opposite force back on the first object

v


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!


Springs

• Forces and energies! • Displacement is linearly

proportional to force applied (F=kx)

• Total energy stored = 0.5kx2 (potential energy)

• Common uses: car shock absorbers, screen door pistons, mousetraps

x

F


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


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!


Formulas• Newton’s Second Law

of Motion

• Conservation of Mechanical Energy

• Potential Energy

• Kinetic Energy

• Spring Force

• Spring Energy

• Momentum (collisions)

• Friction


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!


Additional Resources

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

Documents

Rube Goldberg Machine Design ContestJean Zheng, MIT MuseumJanuary 29, 2005 Rube Goldberg Machine Design Contest Teacher Training Jean Zheng Massachusetts