Mechanical Advantage and Efficiency. Mechanical Advantage A machine’s MA is the number of times a...
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Transcript of Mechanical Advantage and Efficiency. Mechanical Advantage A machine’s MA is the number of times a...
Mechanical Advantage and Efficiency
Mechanical Advantage
• A machine’s MA is the number of times a force exerted on a machine is multiplied by the machine.
• The MA is a ratio between the output and input force
• MA = Output Force / Input Force
If you exert a force of 20 N on a can opener, and the opener exerts a force of 60 N on the can, the ideal mechanical advantage of the can opener is
A. B. C. D.
5%
86%
5%5%
A. 6
B. 2
C. 1200
D. 3
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Mechanical Advantage > 1
• A machine with a mechanical advantage of greater than 1 multiplies the input force.
• Examples: can opener
a ramp
Mechanical Advantage < 1
• A machine with a mechanical advantage of less than 1 does not multiply the force but increases the distance and speed.
• Example: Hockey Stick Paper Fan
Mechanical Advantage = 1
• A machine with a mechanical advantage of 1 means that a machine changes the direction of the force.
• Example: Rope
The mechanical advantage of a machine that changes only the
direction of force is
A. B. C. D.
43%
4%
13%
39%A. 1
B. Less than 1
C. Greater than 1
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Efficiency of Machines• To calculate the efficiency of a
machine, divide the output work by the input work and multiply the result by 100 percent.
• Efficiency = Output work * 100%
Input work
The efficiency of a machine compares
A. B. C. D.
5%0%0%
95%A. Force to mass
B. Output work to input work.
C. Force to friction
D. Friction to mass
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Actual Mechanical Advantage
• The actual mechanical advantage is the mechanical advantage that a machine provides in a real situation.
Ideal Mechanical Advantage
• The ideal mechanical advantage is the mechanical advantage of a machine without friction.
• The more efficient a machine is, the closer the actual mechanical advantage is to the ideal mechanical advantage.
An ideal machine would have an efficiency of
A. B. C. D.
4%
87%
9%
0%
A. 1 percent
B. 10 percent
C. 50 percent
D. 100 percent
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If tight scissors have an efficiency of 50 percent, how much of your
work is wasted overcoming friction?
A. B. C. D.
0%5%
90%
5%
A. All of it
B. None of it
C. One half of it
D. 10 percent of it
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Without friction there would be
A. B. C. D.
30% 30%
9%
30%
A. Less machine efficiency.
B. Greater output work than input work.
C. Greater input work than output work.
D. Equal input and output work.
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