1. Simple Machines Work, Mechanical Advantage and Efficiency

2. Simple Machines  All machines can be classified as or a combination of levers and inclined planes.  Manipulates the Law of Conservation of Energy  The amount of energy that goes in the machine = to the amount of energy that comes out.  Work in = Work out  F in x d in = F out x d out

3. Machines and Work  Machines DO NOT decrease work!!!  They change the Force and distance needed to get a certain amount of work done. FdFdFd

4. Work Done F in F out d in = 1.75 m d out = 0.25 m Fulcrum/ Pivot point 2000 N 1.75 m F in x d in = F out x d out x=0.25 mxF in 2000 N F in = 0.25 mx2000 N 1.75 m = 286 N

5. Mechanical Advantage  How much a machine changes the force  There are 4 variables  F e = “effort force”: how much YOU put in.  F r = “resistance force”: force generated by machine.  d e = “distance effort”: distance effort must travel i.e. length of a lever’s effort arm.  d r = “distance resistance”: distance the resistance must travel i.e. the length of the resistance arm in a lever.

6. Mechanical Advantage FeFe FrFr d e d r Fulcrum/ Pivot point

7. Ideal Mechanical Advantage  Model of a machine in an “ideal” world.  No friction or heat loss.  Ideal mechanical advantage = distance effort/distance resistance.  IMA = d e /d r  This is a ratio so there are no units

8. Mechanical Advantage  In the “real” world energy is lost as friction and heat.  Mechanical Advantage = resistance force/effort force  MA = F r /F e  No units

9. Efficiency  Work out / Work in x 100  The ratio of a machine’s MA to its IMA determines its efficiency.  Efficiency = MA / IMA x 100.

10. Levers  3 lever types  Class 1 lever:  Ex: crowbar FeFe FrFr d e d r Fulcrum/ Pivot point  Label  F e = “effort force”  F r = “resistance force”  d e = “distance effort”  d r = “distance resistance”

11. Levers  Class 2 lever:  Ex: wheel barrow FeFe FrFr d e d r Fulcrum/ Pivot point  Label  F e = “effort force”  F r = “resistance force”  d e = “distance effort”  d r = “distance resistance”

12. Levers Class 3 lever:  Ex: bicep FeFe FrFr d e d r Fulcrum/ Pivot point  Label  F e = “effort force”  F r = “resistance force”  d e = “distance effort”  d r = “distance resistance”

13. Inclined Plane  Example: ramp drdr dede FrFr FeFe

14. Inclined plane Inclined plane wrapped around a cylinder Lever Variation of wheel and axle More simple machines  Wedge:  Screw:  Wheel and axle:  Pulley:

15. Height = 0.5 m Height does not change, only the angle.

16. Height = 0.5 m Scale reads = 300g Car mass = 500g Length = 0.83 m 30 0

17. Height = 0.5 m Scale reads = 3N Car mass = 5N Length = 0.83 m 30 0 Modified test

18. Height = 0.5 m Scale reads = 300g Car mass = 400g Length = 0.66 m 30 0

19. Inclined Plane Example: ramp Force Distance Force drdr dede FrFr FeFe

20. Mechanical Advantage Example 200 N 75N 1 m 4 m FeFe FrFr d e d r

22. 500 N

23. Class 3 leverClass 1 leverClass 2 lever FeFe FrFr dede drdr FeFe FeFe FeFe FrFr FrFr FrFr drdr drdr drdr dede dede dede

24. ForceResistance Fulcrum