Machines Mr. Skirbst Physical Science
What is a machine?
- an instrument that makes work easier
What is a machine? -an instrument that makes work easier WORK INPUT→MACHINE →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 ) (W o is work output; W i is work input)
What is efficiency? -A comparison of work output to work input E = ( W o ) / ( W i ) (W o is work output; W i is work input) “E” NEVER reaches 100% Some “E” always lost (friction)
What is a mechanical advantage?
- 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 thework
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
Fixed Pulley FeFe FrFr
Mechanical Advantage M.A. = ( F r ) / ( F e ) M.A. =
Movable Pulley FrFr FeFe
Mechanical Advantage M.A. = ( F r ) / ( F e ) M.A. =
Fixed and Movable Pulleys FrFr FeFe
Mechanical Advantage M.A. = ( F r ) / ( F e ) M.A. =
Multiple Pulleys FrFr FeFe
Mechanical Advantage M.A. = ( F r ) / ( F e ) M.A. =