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Published byChristine Jordan Modified over 9 years ago
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Simple Machines Simple Machines
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Machine vs. Simple Machine Machine: Any device that makes work easier Simple Machine ◦ A device that does work with only one movement. ◦ There are four main simple machines
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Advantages of Simple Machines Makes work easier by changing the force you exert in size, direction or both. Help overcome gravity and friction
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2 Kinds of Work Work done by the machine (W out ) Work done on the machine (W in ) W out is always smaller than W in due to friction W= f X d (J)
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Applying Force 2 forces when a machine does work: ◦ Effort Force (F e ): the force applied to the machine ◦ Resistance Force (F r ): the force applied by the machine
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Mechanical Advantage The number of times a machine multiplies the effort force MA = resistance force = F r effort force F e The higher the MA the lower the effort put in
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Inclined Plane Flat slanting surface Connects one level to another
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Modified Inclined Planes: Screw Screw ◦ Inclined Plane wound around a rod
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Modified Inclined Planes: Wedge Wedge Inclined plane that moves Inclined Plane that cuts
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Inclined Plane MA Formulas Ideal Mechanical Advantage IMA= de (length of slope) dr (height of slope) D=distance E= effort R=resistance Actual Mechanical Advantage AMA=Fr (mass) Fe (effort) F=force E=effort R=resistance
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Lever Pivots around a fulcrum which can increase force or increase distance Effort arm Resistance arm
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Mechanical Advantage of Levers IMA = length of effort arm = Le length of resistance arm Lr AMA= R E
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Classes of Levers First Class (EFR) ◦ Ex: seesaw Second Class (FRE) ◦ Ex: Wheelbarrow Third Class (REF) ◦ Tweezers Effort Resistance Fulcrum
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Pulley Rope passing over a grooved wheel Changes direction of force or amount of force
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Pulley Can be movable or fixed Block and Tackle: combinations of pulleys to gain a large MA
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AMA= R (resistance E (effort) IMA= Number of supporting strings
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Wheel and Axle Wheel rotating around an axle Ex: Doorknobs, faucets, etc.
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Mechanical Advantage Mechanical Advantage
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MA Formula AMA= R E R=Resistance E=Effort IMA= Rw Ra R=Radius w=wheel a= axle
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