1. Simple Machine: The Pulley

2. Simple Machine Part of Lever Family made with a rope, belt or chain wrapped around a wheel. member of lever family a modified lever point in middle of pulley like fulcrum of a lever rest of pulley is like rigid arm of lever multiple pulleys used to increase the MA

3. Calculating Mechanical Advantage Fixed pulley => MA = 1 moveable pulley = MA≥2 (count # of supporting ropes.) OR MA = Fo/Fi (Output Force/Input Force)

4. Fixed Pulley a pulley in which the wheel does not move. change the direction of the effort force. does not increase the size of the effort force. Fo= Fi; therefore, MA =1. Li = Lo; therefore, MA = 1

5. Fixed Pulley - 1st class lever with an IMA of 1 - Changes the direction of force 10 lb

6. Movable Pulley - 2nd class lever with an IMA = 2 (count the supporting cables) - Force directions stay constant 5 lb 10 lb

7. Pulleys In Combination Fixed and movable pulleys in combination provide mechanical advantage and a change of direction for effort force. 800 lb Movable pulleys in combination provide mechanical advantage without change in effort force direction. 40 lb 20 lb 10 lb 80 lb

8. Moveable Pulley does not change direction of the input force does increase the size of the force pull on the rope, pulley & load come up MA = counting # of ropes that lift load. Typically MA > 2.

9. Pulley System is simply a fixed & moveable pulley put together. MA = to the number of supporting ropes. Typically MA≥3

10. Pulley redirects tension in a rope, which remains constant in system, thus creating advantage. more pulleys added =greater MA each pulley splits amount of force necessary to lift object.

11. Example of Pulleys http://library.thinkquest.org/27948/pulley.ht ml?tqskip1=1&tqtime=1008

12. Mechanical Advantage Fixed Pulley: MA = 1 Moveable Pulley: MA≥ 2 – Count # of supporting ropes – Fo/Fi

13. MA (pulley) – Example #1

14. MA (pulley) – Example #2

15. MA (pulley) – Example #3 MA = 4

16. Eureka: Pulleys http://www.youtube.com/watch?v=TlPWy7q W7oM

17. Question #1 A system of pulleys allows a mechanic to lift an 900 N car. a. If the mechanic exerts a force of 300 N on the pulley system, what is the mechanical advantage of the machine? b. What is the mechanical advantage of the pulley system if the mechanic must exert 500 N of force to lift the car? c. After improving the design of his pulley system, the mechanic can now lift the engine with a MA of 4. How much force is now required to lift the engine?

18. Question #2 A system of pulleys allows Kartik to lift an 1400 N elephant. a. If Kartik exerts a force of 200 N on the pulley system, what is the mechanical advantage of the machine? b. What is the mechanical advantage of the pulley system if Kartik must exert 900 N of force to lift the car? c. After improving the design of his pulley system, Kartik can now lift the engine with a MA of 5. How much force is now required to lift the engine?

19. Question #3 How many supporting ropes does a pulley with a mechanical advantage of 6 have?

20. Question #4 If Faizan does 500J of work using a pulley system and the force exerted is 300 Newtons, then what is the distance travelled?