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