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How Machines do Work

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:

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How Machines do Work

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  1. How Machines do Work Mechanical Advantage and Efficiency

  2. What is a Machine? • Shovel • Wheelbarrow • Bulldozer • Rake

  3. A machineis a device that makes work easier! • Amount of work does not change! What is a Machine?

  4. 2 Types of Machines Simple • Unpowered mechanical device • There are 6: • Lever • Pulley • Wheel and Axle • Incline Plane • Screw • Wedge Compound • A machine that has two or more simple machines

  5. Input Force • The force YOU PUT INTO the machine is called the input force. • It is also called the EFFORT force • In other words: The input includes everything you do to make the machine work. Input Force

  6. Output Force • The force done by the machine is called the output force. • Also called the RESISTANCE • In other words: The output is what the machine does for you. Output Force

  7. Force/Distance Trade Off • Mechanical Advantage: how many times the machine increases your force • (how much the machine makes work easier) • A machine can make work easier by changing either: • Direction • Distance • Force • The amount of work stays the same!!

  8. Changing Direction • When a machine changes the direction of the input force, the amount of force and distance remain the same Input Direction Output Direction

  9. Changing Distance • If you want the machine to increase your distance, you must apply more force over a shorter distance. • Force (F) x distance (d) = Work (W) = Force (F) x distance (d) Input Distance Output Distance

  10. Changing Force • If you want the machine to help you use less force, you must apply the smaller force over a longer distance. • Force (F) x distance (d) = Work (W) = Force (F) x distance (d)

  11. Efficiency of Machines • The efficiencyof a machine tells how well the machine works • Efficiency is always a percent. • The higher the percent, the more efficient the machine is. • 90% • 75% • 50%

  12. Input and Output Work • Frictionalways converts some of the input work to heat and wear, so the output work is always less than the input work. • The more friction in a machine, the less efficient the machine! More Less

  13. Real vs. Ideal Machines • An ideal machine would have an efficiency of 100%. • However, all real machines have an efficiency of less than 100% because some work is wasted due to friction.

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