# Machines Mr. Skirbst Physical Science Topic 06. What is a machine?

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Machines Mr. Skirbst Physical Science Topic 06

What is a machine?

- an instrument that makes work easier

What is a machine? -an instrument that makes work easier WORK INPUTMACHINE OUTPUT

What is efficiency?

-A comparison of work output to work input

What is efficiency? -A comparison of work output to work input E = ( W o ) / ( W i )

What is efficiency? -A comparison of work output to work input E = ( W o ) / ( W i ) E NEVER reaches 100% Some E always lost (friction)

- How much a machine multiplies the effort force

What is a mechanical advantage? -How much a machine multiplies the effort force M.A. = ( F r ) / ( F e ) F r – resistant force F e – effort force

What is a mechanical advantage? The higher the MA, the easier it is to do work

What is a mechanical advantage? Illustrations: Lever:Pulley:

What is a simple machine?

A basic instrument that can increase the mechanical advantage

What is a simple machine? 1.Inclined Plane - a flat, slanted surface - ex. Ramp, door lock

What is a simple machine? 2.Wedge - inclined plane that moves - ex. knife, ax, key

What is a simple machine? 3.Screw - inclined plane around a cylinder - ex. screw, bolt, jar lid

What is a simple machine? 4.Lever - rigid bar free to pivot around a fulcrum - ex. crowbar, paddle, pliers

What is a simple machine? 5.Wheel and Axle - circular object turning around an axle (larger cylinder around smaller cylinder) - ex. Wheel, windmill, door knob

What is a simple machine? 6.Pulley - rope or chain around a grooved wheel and axle - ex. window shade, flag pole, block and tackle

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