1.  Work, Mechanical Advantage, & Simple Machines making jobs easier

2. Journal Entry  What is work?  Is there anyway to make work easier? How?

3. Work Demonstration  Moving Pennies… Any Volunteers?  How does the science of physics define work???

4. Work Definition:  Work is done on an object when a force is exerted on an object that causes the object to move some distance.  No work without motion  No work without force in the same direction  Work is the way we transfer energy  Equation:  Work = force X distance

5. Force  A push or a pull  Measured in metric unit of Newtons  One Newton = ~1/5 lbs  Tool: spring scale  Demo Spring Scale

6. Motion and force  Person does not work on weights – weights do not move  Person does work on weights – weights moved Force on weights Summer Olympics 2000 Sydney Australia By Lou Jones http://www.pricespower.com

7. Direction and force  Horse does not work on the rider – force not in same direction  Horse does work on the cart - force and motion in the same direction Force on person motion Force on cart

8. Calculating work  Work = Force X Distance  F = Force units = Newton, N  d = Distance units = meter, m  W = Work units = Joule, J  J = N x M  Joules = Newton x Meter  Work = Force x Distance  1 Joule = 1 Newton-meter

9. NASA Video  http://www.youtube.com/watch?v=iCqm5uxc2dE&feature=related http://www.youtube.com/watch?v=iCqm5uxc2dE&feature=related  Show ~ 3:30

10. Eureka Video: What is Work?  Eureka Video: Work Eureka Video: Work

11. Calculating work  Work = Force X Distance  F = Force units = Newton, N  d = Distance units = meter, m  W = Work units = Joule, J  J = N x M  Joules = Newton x Meter  Work = Force x Distance  1 Joule = 1 Newton-meter  Conversion: 1kg = 9.8N (You must memorize this conversion)

12. Practice Calculating Work  If you moved a pencil 20 meters using 2.5 Newtons of force, how much work have you done? W = F x d

13. Practice Calculating Work  A force of 800 N is needed to push a car across a lot. If a student pushes the car 40.0 m. How much work is done?

14. Practice Calculating Work  How much work is done in lifting a 60.0-kg person a vertical distance of 10.0 m? (remember: 1kg = 9.8 N)

15. Practice Doing Work  If you exert a force of 5 N on a stack of 20 textbooks that had a mass of 5.10 kg (about 11 pounds) 1 meter, how much work have you done? (remember: 1 kg = 9.8 N)

16. Ugh! Too much work!  Want help?

17. Simple Machine: Examples

18. Why do we use machines?  to reduce the amount of effort or work we exert  to increase our ability to lift or move objects.

19. Kinds of Machines  Simple Machines  Lever, wheel & axle, pulley, inclined plane, screw, wedge  Few or no moving parts  Compound Machines  Consists of two or more simple machines

20. Simple Machine Families  Inclined Plane Family  wedge, inclined plane (ramp), screw  Lever Family  lever, wheel and axle, pulley

21. Simple Machines & Work  A machine…  is a device that does work  does not increase amount work done  makes it easier to do the same amount of work.  Machines make work easier by …  changing force  changing distance  changing the direction of the force.

22. Machines…  Do NOT change the amount of work done

23. Total work does not change  Work = Force x Distance  If a machine allows you to…  force, then distance  distance, then force  apply a force in a different direction, then it doesn’t change how much force you have to apply or how far you move it

24. Mechanical advantage  # of times a force exerted on machine is multiplied by the machine  Mechanical advantage or MA = Output force Input force  If MA > 1, then force, but distance  If MA < 1, then force, but distance  If MA = 1, then neither the force or distance is changed.

25. Eureka! Video: Mechanical Advantage  http://www.youtube.com/watch?v=oWiZ_5qvs7I& NR=1

26. Hey, It’s Tim and Moby  http://www.brainpop.com/science/motionsforcesa ndtime/work/

27. Attack of the Machines!!!

28. Mechanical Advantage: Simple Machines  You will learn about the MA of specific simple machines when each new machine is introduced.

29. Types of simple machines  Inclined plane  Wedge  Screw  Lever  Wheel and axle  pulley Image taken from: http://www.daniel-wright.district103.k12.il.us/ccheifetz/physics.html

30. Inclined plane teacher.scholastic.com/dirtrep/ simple/img/plane.gif

31. Wedge teacher.scholastic.com/dirtrep/ simple/img/wedge.gif

32. Screw teacher.scholastic.com/dirtrep/ simple/img/screw.gif

33. Lever teacher.scholastic.com/dirtrep/ simple/img/lever.gif

34. Wheel and axle teacher.scholastic.com/dirtrep/ simple/img/wheel.gif

35. Pulley teacher.scholastic.com/dirtrep/ simple/img/pulley.gif