Wedge

1. Wheel and Axle Lever Machines Pulley Screw Wedge Inclined Plane

2. What is a Machine? • A device that makes doing work easier • Two divisions • Simple machines • Compound Machines • Work against friction and gravity.

3. How do Machines make work Easier? • Increase Force • (ex: car jacks) • Increase the distance a force is applied • (ex: using a ramp) • Changing the direction of an applied force • (ex: ax blade)

4. Simple Machines • Machines that does work with only one movement of the machine

5. Input force & Output force • Input Force • Force applied to the machine • Symbol = Fin • Output Force • Force applied by the machine • Symbol = Fout

6. Input Work & Output Work • Input Work • Work done by you on a machine • Symbol = Win • Output Work • Work done by the machine • Symbol = Wout

7. Input & Output Work: The Relationship • Input work equals Output work in an ideal machines • Win = Wout • Why? • Law of conservation of Energy • Energy is not created nor destroyed

8. What is Mechanical Advantage? • Is the number of times that a machine increases an input force • Two Versions • Actual Mechanical Advantage • Ideal Mechanical Advantage

9. Mechanical Advantage Mechanical Advantage Link

10. Actual Mechanical Advantage • Determined by measuring the actual forces on a machines • Ratio of the output force to the input force

11. Actual Mechanical Advantage Formula AMA = Fr / Fe • AMA= actual mechanical advantage • Fr= resistance force (output force) • Fe=effort force (input force) • AMA has no unit • Fr & Fe has the unit of “N”

12. AMA Formula Practice 1) What is the actual mechanical advantage of a machine who’s input force is 30-N but produces an output force of 90-N? 2) You test a machine and find that it exerts a force of 10 N for each 2 N of force you exert operating the machine. What is the actual mechanical advantage of the machine?

13. Example Problems: • A worker applies an effort force of 20N to pry open a window that has a resistance force of 500N. What is the mechanical advantage of the crowbar? • Find the effort force needed to lift a 2000N rock, using a jack with a mechanical advantage of 10.

14. Cont… 3. A carpenter uses a claw hammer to pull a nail from a board. The nail has a resistance of 2500N. The carpenter applies an effort force of 125N. What is the mechanical advantage of the hammer? 4. A force of 500N is needed to lift a 200kg stone, what is the MA of the simple machine?

15. Cont… 5. What is the force required to lift a 12kg object if the MA of the machine is 5? 6. What is the efficiency of a machine that 500 J of work was put into the machine and it produced 400 J of work?

16. Ideal Mechanical Advantage • Is the mechanical advantage in the absence of friction • Because friction is always present, the actual mechanical advantage of a machine is always less than the Ideal

17. Ideal Mechanical Advantage Formula IMA = de / dr • IMA = ideal mechanical advantage • de = displacement of effort force (input distance) • dr = displacement of resistant force (output distance) • IMA has no unit • de and dr has the unit of meters

18. IMA Formula Practice 1) A woman drives a car up onto wheel ramps to perform some repairs. If she drives a distance of 1.8 meters along the ramp to raise the car 0.3 meter, what is the IMA? 2) A construction worker moves a crowbar through a distance of 4 meters to lift a load 0.5 meter off the ground. What is the IMA of the crowbar?

19. Calculate IMA: 3 m 9 m . IMA = 7. You use a crow bar 140 cm long as a lever to lift a large rock. The rock is 20 cm from the fulcrum, what is the IMA of the lever?

20. What is efficiency? % • The percentage of work input that becomes work output • Because there is always some friction, the efficiency of any machine is always less than 100 percent

21. Efficiency Formula • Wout = work output (J) • Win = work input (J)

22. Efficiency Formula Practice 1) You have just designed a machine that used 1000 J of work from a motor for every 800 J of useful work the machine supplies. What is the efficiency of your machine?

23. 6 Types of… Machines usually work against GRAVITY and FRICTION.. Example: 1. Lifting a car 2. Opening a jar lid

24. Click on the dude to learn more. Inclined Plane A sloping surface (ex: ramp)

25. Screw A screw is an inclined plane wrapped around a post. Ex: A Jar lid Click on the light bulb to learn more.

26. Wedge Two inclined planes make a wedge. An inclined plane with one or two sloping sides (ex: knife)

27. Wheel and Axle Click on the windmill to learn more. A shaft/axle attached to the center of a larger wheel so that both rotate together (ex: door knobs) Wheel Axle

28. Pulleys Wheel This box is easier to lift because of the pulley. Click on it to learn more. Rope

29. PULLEY a grooved wheel with a rope or chain running along the groove (ex: wishing well)

30. Click Here to Learn More Levers Lever Load Fulcrum

31. LEVERSa bar that is free to pivot or turn about a fixed point Resistance arm – part of lever that exerts resistance force “LOAD” Effort Arm – part of lever where force is applied “FORCE” FULCRUM – fixed point of a lever

32. 3 TYPES OF LEVERS Based on the positions of the effort force, resistance force and the fulcrum…

33. FIRST CLASS Fulcrum is located between the resistance and the effort force (RFE) http://www.usoe.k12.ut.us/curr/science/sciber00/8th/machines/sciber/lever1.htm

34. SECOND CLASS Resistance is between the effort force and the fulcrum (FRE) http://www.usoe.k12.ut.us/curr/science/sciber00/8th/machines/sciber/lever2.htm

35. THIRD CLASS Effort force is between the resistance force and the fulcrum. (FER) MA is always less than one - ??? http://www.usoe.k12.ut.us/curr/science/sciber00/8th/machines/sciber/lever3.htm

36. Which is Which??

37. What are Compound Machines? • When two or more simple machines operate together • Example: Can Opener • Wheel & Axle • Lever • Wedge