2. p. 287 2. MA= OF/IF 3. A) MA= OF/IF B) MA= OF/IF
MA= 15000N / 350 N = 42.9
3. A) MA= OF/IF
MA= 10N / 5.2 N = 1.8
SR= ID/OD
1.0 M / 0.5 M = 2.0
B) MA= OF/IF
MA= 20.0 N / 7.0 N =2.9
SR= 30.0 M / 10.0 M= 3.0

3. P. 287 3C) MA= OF / IF 4. Efficiency = (MA / SR) x 100%
MA= 4.0N / 10.0 N =0.4
SR= ID/OD
SR= 0.4M / 0.8M= 0.5
4. Efficiency = (MA / SR) x 100%
A) 90%
B) 97%
C) 96%
5. Friction opposes the motion of an object and increases the force required for movement. It also creates waste heat in a system.

4. The science of work
2.2

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Work
Work – done when a force acts on an object to make the object move.
- Movement is needed before one can say that work has been done.
- Amount of work done depends on 2 things:
1) amount of force exerted on the object
2) distance the object moved in the direction of the applied force.

6. Work Work (N*m) = Force (N) * Distance (m) N*m is called a Joule (J)
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Work
Work (N*m) = Force (N) * Distance (m)
 N*m is called a Joule (J)
The joule is also used in calculating energy

8. Work Questions

9. Work Answers 250 NM or 250 J 500 N 80 000 NM or 80 000 J 500 J 10 N

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Energy and Work
 Energy and work are closely related, can not have one without the other.
Ex) Car – needs energy (gasoline) in order to work (move)
Machines help us do work by transferring energy.

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Work and Machines
 Using a machine does not decrease the amount of work, it decreases the force.
Ex) Work Input = Work Output
- This equation is affected by friction (just like mechanical advantage)
- Here is another way of calculating efficiency.
Work Output
Efficiency = ________________
Work Input

14. Work Efficiency

15. Work Efficiency Answers
80%
60%
67%
50% 60
85.7
80 J

17. Formulas to Know MA= Output force/Input force S=Distance/Time (m/s)
SR= Input distance/ output distance
Efficiency= (Output/ Input)X 100% OR MA/SR
W= F x D (Nm)

18. http://streaming. discoveryeducation. com/search/assetDetail. cfm

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Practice Questions
P. 292
1, 2, 6, 7, 8, 9