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Machines

Machines. What is a machine? How do you calculate the M.A. and Efficiency of a machine?. INPUT. Input Force – force you exert on a machine Input distance – how much the input force moves the machine Input Work = Input F x Input d. OUTPUT.

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Machines

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  1. Machines What is a machine? How do you calculate the M.A. and Efficiency of a machine?

  2. INPUT • Input Force – force you exert on a machine • Input distance – how much the input force moves the machine • Input Work = Input F x Input d

  3. OUTPUT • Output Force – the force the machine exerts on an object • Output distance – the distance over which the machine exerts the output force • Output Work = Output F x Output d

  4. Work and Machines • A machine makes work easier by changing force, distance, or direction • It DOES NOT multiply work • The amount of output work can never be greater than the amount of input work

  5. What is a machine? • A machine is a device that allows you to do work in a way that is easier. A machine changes at least one of three factors: • Force • Distance • Direction

  6. Changing Force - Output force > Input force - Output distance < Input distance - Example: ramp - f x D  F x d

  7. Changing Distance • Output Force < Input Force • Output distance > Input distance • Examples: hockey stick, baseball bat, chopsticks, pedaling a bike • F x d  f x D

  8. Changing Direction • No change in force or distance • Only changes direction • Example: weight lifting machine • F x d  d x F

  9. Mechanical Advantage • Definition: the number of times a machine increases a force exerted on it • Formula: MA = Output F/Input F

  10. Mechanical Advantage • Increasing Force – when the output force is greater than the input force, the MA of the machine is > 1

  11. Mechanical Advantage • Increasing Distance – when the machine increases d, the output force is less than the input force, so the MA is < 1

  12. Mechanical Advantage • Changing Direction – if only the direction changes, the input force will be the same as the output force, so MA = 1

  13. Calculating Mechanical Advantage

  14. Efficiency • MA is ideal • In the real world, output work is always less than input work • Efficiency compares output work and input work • % - higher is more efficient

  15. Efficiency • Friction – in every machine, some work is wasted overcoming the force of friction • Equation: • E = (output W/input W) x 100%

  16. Real vs Ideal • 100% efficiency is ideal • In reality, measured efficiency is less than 100%

  17. Questions

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