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Rube Goldberg Machine Design Contest Teacher Training Jean Zheng Massachusetts Institute of Technology Department of Mechanical Engineering January 29, 2005 Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 Topics • • • • • • • • Engineering problem solving process Measurement Systems Statics and Dynamics Energy Springs Collisions Friction Formulas Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 Engineering Problem Solving Process 1. 2. 3. 4. 5. 6. 7. 8. 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 won’t move with it.” Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 Measurement System • English – commonly used in the US • Metric – adopted by the rest of world • 1 mile = 1760 yards 1 yard = 3 feet 1 foot = 12 inches • 1 1 1 1 kilometer = 1000 meters meter = 10 decimeters decimeter = 10 centimeters 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) Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 Statics and Dynamics • • Statics – things that are in equilibrium Dynamics – things that are in motion Newton’s Laws of Motion v – 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 Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 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! Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 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 Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest x F January 29, 2005 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 Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 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! Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 Formulas • Newton’s Second Law of Motion • Conservation of Mechanical Energy • Potential Energy • Kinetic Energy • Spring Force • Spring Energy • Momentum (collisions) • Friction Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 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! Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005 Additional Resources • • • • • • • High school physics books Other teachers at your school MIT student mentors MIT Museum www.rube-goldberg.com Other online resources Teammates! Jean Zheng, MIT Museum Rube Goldberg Machine Design Contest January 29, 2005