PS 8 Notes

SIMPLE MACHINES. p. 124-155

Work=

The energy used to MOVE an object.

Work equation=

Force X distance.

The unit is Newtons X meters = joules. 

Power=

The amount of work done /second.

Power = Work

                Time

The units are: Watts = joules

                                                                          sec

Machine-

A device that makes doing work easier

Simple machine=

A device that does work with only one movement.

Compound Machines=

A combination of two or more simple machines.

Mechanical advantage= (136)

A measure of how much force you gain by using a machine rather than doing the work without the machine. (Ex. A jack for a car.)

A measure of how much less force you use.

Effort force= (Input force)p.134

The force you put on the machine.

Resistance force= (Output force)

The force the machine puts on the object.

*Effort distance=

The distance over which your effort acts.

*Resistance distance=

The distance over which the object moves.  

** Work in = Work out

Force X distance(effort) = Force X distance(resistance)

Six types of Simple Machines

1.     Inclined plane.= a sloping surface, such as a ramp that reduces the amount of force required to do work

2.     Wedge= an inclined plane with one or two sloping sides

3.     Screw= an inclined plane wrapped in a spiral around a cylindrical post

4.     Lever= a bar that is free to pivot or turn around a fixed point

5.     Wheel and axle.= a simple machine consisting of a shaft or axle attached to the center of a larger wheel, so that the wheel and axle rotate together

6.     Pulley.= a grooved wheel with a rope, chain, or cable running along the groove.

Three classes of levers

First class= R               E        

                                  F

Two examples are scissors and a teeter-totter.(Screw driver as a lever and the neck nodding)

Second Class= _       R    E 

                F

Two examples are wheel barrow and nut cracker.(Ankle as you stand on your toes.)

Third Class= _      E     R

                   F

Two examples are tweezers and a shovel.(Forearm)

R= Resistance

F= Fulcrum or point of pivot.

E= Effort provided by the person.

Power= 

The rate at which work is done.

Power = Work =Watt     

           Time

One watt is equal to one joule of work done.

Efficiency=

The comparison of the work put into a machine versus the work the machine puts out.

Efficiency =Work out(100) = %

                  Work in