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