Answers - Plymouth School District

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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.
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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.
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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%
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