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Simple Machines Test Review Power 1. Define Power The rate of doing work 2. What is the Power formula P = W/t or P = (F·d)/t 3. What are the power units? Watts or kiloWatts 4. How many watts equals 1.53 kilowatts 1,530 Watts 5. Calculate the time required to lift a 600 N box up 0.5 m if 20 watts of power is used? 15 seconds Inclined Planes 6. Give one example of an inclined plane Answers vary 7. Fr is usually the _WEIGHT of the object If Tommy weighs 100 N and Robert is pushing him up a hill 6 m high and 11 m long. 8. 9. 10. 11. What is the theoretical MA of the hill? MA = l/h = 11 m/ 6m = 1.83 How much effort force must Robert exert? Fe = Fr/MA = 100N/1.83 = 54.6 N How much work is done to Tommy Wout = Fr x dr = 100 N x 6 m = 600 Nm Name one advantage of the inclined plane. Multiplies effort force Levers 12. The force applied by you to the machine is the EFFORT FORCE. 13. The point about which a lever pivots is called the FULCRUM. 14. The distance from the fulcrum to the point where the resistance force acts is the RESISTANCE ARM. 15. Calculate the MA of the pictured lever. MA=le/lr = 60 cm/20 cm = 3 16. What class lever is the pictured lever. 1st Class 17. Name one disadvantage of the pictured lever greater effort distance required General Define the wedge TWO INCLINED PLANES PUT TOGETHER Define the lever A BAR THAT IS FREE TO PIVOT AROUND A FIXED POINT What is a simple machine A MACHINE CONSISTING OF ONLY ONE PART OR UNIT Define Mechanical Advantage THE NUMBER OF TIMES A MACHINE MULTIPLIES YOUR EFFORT FORCE 22. Define a pulley A GROOVED WHEEL THAT IS FREE TO ROTATE ON AN AXLE 23. A force exerted by a machine is a(n) RESISTANCE FORCE. 18. 19. 20. 21. Pulleys 24. Give one example of a pulley used outside of school. (ANSWERS VARY) 25. Find the MA of a multiple pulley system with 2 quad pulleys and the effort force is pulling down 4 26. What is the MA of the pictured pulley system? 8 27. Name 1 advantage of the pictured pulley system CHANGES DIRECTION OR MULTIPLIES EFFORT FORCE 28. Name 1 disadvantage of the pictured pulley system EFFORT DISTANCE IS LONGER 29. Calculate the Effort Force required to raise the object. Fe = Fr/MA = 1000 N/8 = 125 N Efficiency If a man pushes a 3000 N piano up a 3 m long inclined plane to raise it to his first floor .5 meters high and he exerts 900 N of effort force. 30. What is the Work input of the man? Win = Fe·de = 900 N · 3 m = 2700 Nm 31. What is the Work output of the machine? Wout = Fr · dr = 3000 N · .5 m = 1500 Nm 32. What is the theoretical MA of the plane? MA = l/h = 3 m / .5 m = 6 33. What is the actual MA of the plane? MA = Fr/Fe = 3000 N / 900 N = 3.3 34. What is the efficiency of the inclined plane? Eff = (Wout/Win) · 100 = (1500 Nm / 2700 Nm) · 100 = .5555 · 100 = 56%