02.02.2012 - Simple Machines

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Adventure in Science is about exploring our world by doing. Each Saturday during the school year we have hands-on sessions hosted by local experts on some aspect of science or engineering that they find exciting or interesting. During these sessions the students get to experiment with the tools or ideas involved to better understand how they really work. Sometimes those ideas can grow into something new and make a difference in the world. Who says science isn't fun?

During this session we taught kids about the physics of simple machines.
http://www.adventureinscience.org/

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02.02.2012 - Simple Machines

  1. 1. Simple Machines! Adventures in Science February 4th, 2012
  2. 2. What is a Machine?
  3. 3. The Six Simple Machines 1. 2. 3. 4. 5. 6. Lever Pulley Inclined plane Wedge Screw Wheel
  4. 4. Who uses simple machines?
  5. 5. What defines a Machine? Definitions: • An apparatus using or applying mechanical work to perform a particular task. • A device that transmits or modifies force. In other words… Machines make work easier by… reducing force!
  6. 6. Machines make work Easier • Work is how much energy you have to exert to move something against a force for a distance. Distance Mass Gravity (acceleration)
  7. 7. Simple machines do NOT reduce the amount of work • They make doing that Work easier… • by reducing Force… • in exchange of increasing the Distance.
  8. 8. What are Force, Distance, and Work? Force = Mass x Acceleration Work = Force x Distance Distance Mass Gravity (acceleration) = 1 meter = 5 kg = 10 m/s2
  9. 9. Force = Mass x Acceleration • How much force do you need to move this block? • F=mxa F = 5kg x 10m/s = 50 N • We need to exert 50 N of force to move this block! 2 Mass Gravity (acceleration) = 5 kg = 10 m/s2
  10. 10. Newton is a unit of Force!! •F = m * a 2 •N = kg*m/s
  11. 11. What if we want to put the block on the table? • We will need to exert Force for a Distance to put the block on the table. This is Work! Distance Mass Gravity (acceleration) = 1 meter = 5 kg = 10 m/s2
  12. 12. Work = Force x Distance • Force = Mass x Acceleration • Work = Mass x Acceleration x Distance • Work = 5kg x 10m/s x 1m = 2 Distance Mass Gravity (acceleration) 50 J = 1 meter = 5 kg = 10 m/s2
  13. 13. Joule is a unit of Work! • W = m * a * d = mad • J = kg * m/s2 * m = kg*m2/s2 = Joule James Prescott Joule
  14. 14. I am very weak!!! • • • • • • I can only exert 5N of Force.  Could I still put the block on the table? Yes! With a simple machine!! 
  15. 15. Introducing the [drum roll]… Inclined Plane!!! Mass
  16. 16. • Before with no Inclined Plane… • I had to counteract all of the acceleration due to gravity! Distance Mass Gravity (acceleration)
  17. 17. The Inclined Plane allows me to push against only a fraction of gravity! Distance Mass Gravity (acceleration)
  18. 18. Here’s the proof: • F=m*a • F = 5kg * 1 m/s2 = 5 N • BUT!! Distance = 10 meters Mass Gravity (acceleration) = 5 kg = 1 m/s2 YAY, I can lift it!
  19. 19. We traded off Force for Distance • Work = mass * acceleration * distance • Work = 5kg x 1m/s x 10m = 2 50 J I am doing: • the same amount of Work with LESS FORCE!! Distance = 10 meters Mass Gravity (acceleration) = 5 kg = 1 m/s2
  20. 20. Simple Machines • Make it possible to do the same amount of work • But use less force. • Therefore: • Simple Machines make Tasks Easier!
  21. 21. The Pulley • Benefit: – Reduces force to lift objects. • Trade-off: – The longer the rope, the easier to lift
  22. 22. What are some real life examples of Pulleys?
  23. 23. Pulley Activity
  24. 24. The Wheel • Benefit: – Reduces friction associated with sliding • Trade-off: – The larger the wheel, the lower the friction… – The smoother the ride
  25. 25. What are real-life examples of wheels?
  26. 26. Wheel Activity
  27. 27. The Inclined Plane • Benefit: – Reduces actionable component of gravity • Trade-off: – The longer the ramp, the lower the force to ascend
  28. 28. What are some examples of inclined planes?
  29. 29. Inclined Plane Activity
  30. 30. The Screw • Benefit • Trade-off
  31. 31. What are some examples of screws?
  32. 32. Screw Activity
  33. 33. The Lever • Benefit • Trade-off
  34. 34. What are some examples of Levers?
  35. 35. Lever Activity
  36. 36. What are some examples of Wedges?
  37. 37. The Wedge • Benefit • Trade-off
  38. 38. Wedge Activity

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