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What is a Machine? Effort force vs. Resultant Force Mechanical Advantage and Efficiency

MACHINES. What is a Machine? Effort force vs. Resultant Force Mechanical Advantage and Efficiency Simple and compound machines Review of simple machines lever, inclined plane, pulley, wheel and axle. Machines. What is a machine?

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What is a Machine? Effort force vs. Resultant Force Mechanical Advantage and Efficiency

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  1. MACHINES • What is a Machine? • Effort force vs. Resultant Force • Mechanical Advantage and Efficiency • Simple and compound machines • Review of simple machines • lever, inclined plane, pulley, wheel and axle

  2. Machines What is a machine? • Makes work easier by changing the size or direction of the force Effort force • Force applied TO a machine Resultant force • Force applied BY a machine

  3. Machines Few moving parts and change the direction of force

  4. Machines Simple Machines- make work easier • Inclined plane • Wedge • Screw • Wheel and Axle • Pulley • Lever (1st, 2nd, 3rd class) Compound Machines- 2 or more simple machines • Gears (wheels and axles with teeth) • Scissors (lever and wedge)

  5. Simple Machines – Inclined Plane Ramp Reduce the effort by increasing the distance

  6. Simple Machines – Wedges 2 inclined planes back to back Changes direction of force Used to split, cut, join, or tighten Ex. Axe, knives, zipper, door stop

  7. Simple Machines – Screw • A screw is an inclined plane wrapped around a shaft or cylinder. • The inclined plane allows the screw to move itself when rotated.

  8. Simple Machines – Wheel and Axle Changes the amount of force needed • The axle is a rod that goes through the wheel which allows the wheel to turn • Gears are a form of wheels and axles

  9. Simple Machines – Pulley Fixed pulley • Just changes direction • MA =1, no advantage Moveable Pulley • MA does exist..why?

  10. Simple Machines – Lever

  11. Simple Machines – Lever 1st Class – Fulcrum in the middle, effort and load at either end ex. See Saw 2nd Class- Fulcrum at the end, effort at the end, Load elsewhere ex. bottle opener 3rd Class- Fulcrum at the end, effort in the middle, load elsewhere ex. fishing pole

  12. Machines Efficiency • % of how much work you do, actually does the desired work • (Work output / work input)x100 • No machine is 100% • Energy loss due to heat, friction

  13. Machines Mechanical Advantage – measures how well a machine works – NO UNITS!! • Ratio of resistance force / effort force = # of times a machine increases effort force • Ideal Mechanical Advantage (Theoretical) • Assumes perfect machine and no loss • Actual Mechanical Advantage (Real) • Takes into account real factors such as lost energy- friction, heat

  14. Machines Mechanical Advantage (MA) • Change the direction of force MA = 1, force is the same but in different direction • Increase the distance W=Fxd, if d is bigger, F is smaller to get same W • Change the Force needed Increase the output force but keep input the same

  15. Mechanical Advantage (MA) Revisited Mechanical Advantage (MA) • Change the direction of force MA = 1, force is the same but in different direction Ex. Fixed pulley • Increase the distance W=Fxd, if d is bigger, F is smaller to get same W Ex. Inclined plane • Increase the Force Increase the output force but keep input the same Ex. Lever, gears

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