1. Work, Mechanical Advantage and Efficiency Essential Question: What is the relationship between IMA & MA

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

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

4. 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 m x F in 2000 N F in = 0.25 m x 2000 N 1.75 m = 286 N

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

6. FeFeFeFe FrFrFrFr d e d r Fulcrum/ Pivot point

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

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

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

10. 3 lever types 3 lever types Class 1 lever: Class 1 lever: Ex: crowbar 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. Class 2 lever: Class 2 lever: Ex: wheel barrow 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. Class 3 lever: Ex: bicep 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. Example: ramp drdr dede FrFr FeFe

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