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Machines
Mr. SkirbstPhysical Science
Topic 06
What is a machine?
What is a machine?
- an instrument that makes work easier
What is a machine?
- an instrument that makes work easier
WORK WORKINPUT → MACHINE → OUTPUT
What is efficiency?
What is efficiency?- A comparison of work output
to work input
What is efficiency?- A comparison of work output
to work inputE = ( Wo ) / ( Wi )
What is efficiency?- A comparison of work output
to work inputE = ( Wo ) / ( Wi )
• “E” NEVER reaches 100%• Some “E” always lost (friction)
What is a mechanical advantage?
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. = ( Fr ) / ( Fe )
Fr – resistant force
Fe – effort force
What is a mechanical advantage?
The higher the MA, theeasier it is to do work
What is a mechanical advantage?Illustrations:Lever: Pulley:
What is a simple machine?
What is a simple machine?
A basic instrumentthat 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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