how do machines work?. what is a machine? allows you to do work in a way that is easier can be quite...
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![Page 1: How do machines work?. What is a machine? Allows you to do work in a way that is easier Can be quite simple A machine changes at least one of three factors…](https://reader034.vdocument.in/reader034/viewer/2022051819/551bdd4c550346b9588b5bd6/html5/thumbnails/1.jpg)
How do machines
work?
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What is a machine?
• Allows you to do work in a way that is easier
• Can be quite simple
• A machine changes at least one of three factors…
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The 3 Factors of Work
1. Amount of force you exert
2. The distance over which you exert your force
3. The direction in which you exert your force
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Input and Output Forces
• Remember… when you use a machine to do work, you exert a force over some distance.
• The force you exert on the machine is the input force.
• The force the machine exerts on an object is called the output force.
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The output work done by the shovel can never be greater than the input work done by the gardener.
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Input and Output Work
• Input force times input distance is called the input work.– Done by the person– Think “I” do input work
• Output force times output distance is called the output work– Done by the machine
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• The output work done by the shovel can never be greater than the input work done by the gardener.
• Input work and output work can vary depending on the distance the force exerted.
• Small input force exerted over a long distance = large output force exerted over a short distance
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Making Work EasierBy Changing
Force, Distance or Direction
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Changing Force
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Changing Distance
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Changing Direction
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Mechanical Advantage
• Mechanical advantage is the number of times a machine increases a force exerted on it.– Think: “How was the force changed?”
MA
OF
IF
No units! : )
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Mechanical Advantage
• If MA is over 1: – Force is multiplied! (output force more than
input, output distance is less)• If MA is less than 1 – Distance is multiplied! (output force less than
input, so output distance is more)• If MA = 1– Machine only changes direction – force and
distance are the same for input and output
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Efficiency of Machines
• Assuming the input work is exactly equal to the output work is ideal, this is not always the case
• The efficiency of a machine compares the output work to the input work.
• Efficiency is expressed as a percent.• The higher the percent, the more efficient the
machine is.
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Efficiency of Machines
What may be the cause of having
a less efficient machine?
Consider the difference between a new pair of garden shears and an
old rusty pair of shears.
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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.
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Calculating Efficiency
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Calculating Efficiency
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Real vs. Ideal Machines
• An ideal machine is 100% efficient.– Does not exist!
• A real machine is less than 100% efficient.