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Types of Simple Machines

Types of Simple Machines. Definition of Simple Machine: A device that accomplishes work in only 1 movement. Levers (Review). 1 st class: Ex: scissors 2 nd class: Ex: Wheelbarrow 3 rd class: Hockey Stick or broom. Mechanical Advantage (MA).

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Types of Simple Machines

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  1. Types of Simple Machines Definition of Simple Machine: A device that accomplishes work in only 1 movement.

  2. Levers (Review) • 1st class: • Ex: scissors • 2nd class: • Ex: Wheelbarrow • 3rd class: • Hockey Stick or broom

  3. Mechanical Advantage (MA) • How much a simple machine multiplies the effort force (making the work easier) • MA<1 :machine is ineffective (makes work harder) • MA=1 :does not make work easier or harder, just changes direction of force applied • MA >1 : makes work easier • General equation for MA: • MA = effort force (Fe) ÷ resistance force (Fr) • MA for levers: • MA = length of effort arm ÷ length of resistance arm

  4. Wheel and Axle • 2 wheels of different sizes that rotate together • Like a lever • Effort force applied to larger wheel while smaller wheel supplies the resistance force • Radius of the wheel: effort arm • Radius of the axle: resistance arm • Fulcrum: center of axle • Gears are a modified wheel and axle

  5. Wheel and Axle (continued) • Example for Wheel and Axle: • MA = radius of wheel ÷ radius of axle = rw ÷ ra • Sample problem: • An automatic steering wheel has a diameter of 48 cm. It is used to turn a steering column with a radius of 4cm. What is the MA? 24cm ÷ 4cm = 6 (no units)

  6. Inclined Plane • Sloping surface used to raise objects • MA for inclined plane = length of slope ÷ height of slope = l ÷ h • Example: a ramp • Types of moving inclined planes: • Screw • wedge

  7. Moving Inclined planes • Screw • Inclined plane wrapped around a cylindrical part (like a spiral staircase) • Screw rotates or moves • Wedge • Inclined plane with one or two sloping sides • Ex: chisel, knife, ax • Material moves in place, wedge moves through it

  8. Pulleys • Grooved wheel with a rope on a chain running along the groove • Similar to a 1st class lever – instead of the bar of a lever, a pulley has a rope. • Axle of pulley acts like fulcrum • The two sides of the pulley are like the effortand resistance arms • Effort: where you pull down • Resistance: what you’re lifting (ex: a bucket)

  9. Pulleys continued • Two main types: • Fixed • attached to something that doesn’t move • Changes direction of the effort force (Fe) • Does not multiply the force • M=1: force input = force output • Examples: pulley at the top of a flag pole • Moveable • Multiplies the force • MA>1 (1 N effort force lifts a weight of 2N (resistance))

  10. Some Uses for Simple Machines • Bionics • Replacement human limbs or joints (levers, etc.) • Lifting heavy objects • Cranes for constructing buildings (pulleys) • Elevators (pulleys) • Pencil sharpener (wheel and axle) • Cars (wheel and axle) • Building cool Rube Goldberg machines!

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