how machines do work
DESCRIPTION
How Machines do Work. Mechanical Advantage and Efficiency. What is a Machine?. Shovel Wheelbarrow Bulldozer Rake. A machine is a device that makes work easier! Amount of work does not change!. What is a Machine?. 2 Types of Machines. Simple Unpowered mechanical device There are 6: - PowerPoint PPT PresentationTRANSCRIPT
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How Machines do Work
Mechanical Advantage and Efficiency
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What is a Machine?
0 Shovel0 Wheelbarrow0 Bulldozer0 Rake
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What is a Machine?
0A machine is a device that makes work easier!0Amount of work does
not change!
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2 Types of MachinesSimple
0Unpowered mechanical device0There are 6:
0Lever0Pulley
0Wheel and Axle0 Incline Plane
0Screw0Wedge
Compound0A machine that has two or
more simple machines
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Input Force0The force YOU PUT INTO the machine is called the
input force.
0It is also called the EFFORT force
0In other words: The input includes everything you do to make the machine work.
Input Force
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Output Force0The force done by the machine is called the
output force.
0Also called the RESISTANCE
0In other words: The output is what the machine does for you.
Output Force
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Force/Distance Trade Off0Mechanical Advantage: how many times the
machine increases your force 0(how much the machine makes work easier)
0A machine can make work easier by changing either:0Direction0Distance 0Force
0The amount of work stays the same!!
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Changing Direction0When a machine changes the direction of the
input force, the amount of force and distance remain the same
InputDirection
Output Direction
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Changing Distance0If you want the machine to increase your distance,
you must apply more force over a shorter distance.
0Force (F) x distance (d) = Work (W) = Force (F) x distance (d)Input Distance
OutputDistance
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Changing Force0 If you want the machine to help you use less
force, you must apply the smaller force over a longer distance.
0Force (F) x distance (d) = Work (W) = Force (F) x distance (d)
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Efficiency of Machines
0The efficiency of a machine tells how well the machine works
0Efficiency is always a percent.
0The higher the percent, the more efficient the machine is.090%075%050%
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Input and Output Work0Friction always converts some of the input work to heat
and wear, so the output work is always less than the input work.
0The more friction in a machine, the less efficient the machine!
More
Less
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Real vs. Ideal Machines0An ideal machine would have an efficiency of 100%.
0However, all real machines have an efficiency of less than 100% because some work is wasted due to friction.