1. Machines Mr. Skirbst Physical Science

2. What is a machine?

3. - an instrument that makes work easier

4. What is a machine? -an instrument that makes work easier WORK INPUT→MACHINE →OUTPUT

5. What is efficiency?

6. -A comparison of work output to work input

7. What is efficiency? -A comparison of work output to work input E = ( W o ) / ( W i )

8. What is efficiency? -A comparison of work output to work input E = ( W o ) / ( W i ) (W o is work output; W i is work input)

9. What is efficiency? -A comparison of work output to work input E = ( W o ) / ( W i ) (W o is work output; W i is work input) “E” NEVER reaches 100% Some “E” always lost (friction)

10. What is a mechanical advantage?

11. - How much a machine multiplies the “effort force”

12. What is a mechanical advantage? -How much a machine multiplies the “effort force” M.A. = ( F r ) / ( F e ) F r – resistant force F e – effort force

13. What is a mechanical advantage? The higher the MA, the easier thework

14. What is a mechanical advantage? Illustrations: Lever:Pulley:

15. What is a simple machine?

16. A basic instrument that can increase the mechanical advantage

17. What is a simple machine? 1.Inclined Plane - a flat, slanted surface - ex. Ramp, door lock

19. What is a simple machine? 2.Wedge - inclined plane that moves - ex. knife, ax, key

22. What is a simple machine? 3.Screw - inclined plane around a cylinder - ex. screw, bolt, jar lid

24. What is a simple machine? 4.Lever - rigid bar free to pivot around a fulcrum - ex. crowbar, paddle, pliers

27. What is a simple machine? 5.Wheel and Axle - circular object turning around an axle (larger cylinder around smaller cylinder) - ex. Wheel, windmill, door knob

29. What is a simple machine? 6.Pulley - rope or chain around a grooved wheel and axle - ex. window shade, flag pole, block and tackle

33. Fixed Pulley FeFe FrFr

34. Mechanical Advantage M.A. = ( F r ) / ( F e ) M.A. =

35. Movable Pulley FrFr FeFe

36. Mechanical Advantage M.A. = ( F r ) / ( F e ) M.A. =

37. Fixed and Movable Pulleys FrFr FeFe

38. Mechanical Advantage M.A. = ( F r ) / ( F e ) M.A. =

39. Multiple Pulleys FrFr FeFe

40. Mechanical Advantage M.A. = ( F r ) / ( F e ) M.A. =