1. Goal 7 Work and Mechanical Advantage

2. What is Work?
__WORK__ is when you exert a force on an object that causes the object to move some distance.
Examples are Pushing a child in a swing, Picking a backpack up off the floor.
No Work Without Motion
To do __WORK__ on an object, the object __MUST__ move some distance as result of your force.
If the object __DOES NOT MOVE__, __NO__ work is done, __NO MATTER__ how much force is exerted.

3. Force in the Same Direction
To do __WORK__ on an object, the __FORCE__ you exert must be in the __SAME__ direction as the object’s motion.
Carrying something: Since the force on the object is __VERTICAL__ () and the __MOTION__ is __HORIZONTAL__ ( ), you __DON’T__ do any work on the object as you carry it.

4. Calculating Work
The amount of work done on an object can be determined by multiplying force times distance.
Work = __FORCE__ X __DISTANCE__
Units of Measure: Force= __NEWTON’S__ ,Distance= __METER__ , Work = __JOULE’S__
BrainPop – Work (2:49)

5. POWER __POWER__ is the rate at which work is done.
Power equals the amount of __WORK__ done on an object in a unit of __TIME__
More __POWER__ in same __TIME__ means __MORE WORK__
Calculating Power
Power = __WORK__ / __TIME__ or __FORCE X DISTANCE__ / __TIME__
Power Unit
Work is measured in __JOULES__ and time is measured in __SECONDS__, So a Joule per Second = __WATTS__
Brain Pop – Power (3:27)

6. How Machines DO Work
A __MACHINE__ is a device that allows you to do work in a way that is easier.
3 ways a machine makes work __EASIER__: amount of __FORCE__ you exert, the __DISTANCE__ over which you exert your force, or the __DIRECTION__ in which you exert your force.

7. Input and Output Forces Input and Output Work
The force you exert on the machine is called the __INPUT FORCE__
Input force __MOVES__ the machine
The machine does work over a distance, called the __OUTPUT FORCE__
__INPUT FORCE__ X __INPUT DISTANCE__ = Input Work
__OUTPUT FORCE__ X __OUTPUT DISTANCE__ = Output Work

8. Mechanical Advantage
__MECHANICAL ADVANTAGE__ is the number of times a machine __INCREASES__ a force exerted on it.
Mechanical Advantage = __OUTPUT FORCE__ / __INPUT FORCE__
Eureka! (4:51)

9. Changing Force
When a machine __INCREASES__ force, you must exert the __INPUT FORCE__ over a greater distance.
When the __OUTPUT__ force is greater than the __INPUT__ force, the M.A. of a machine is __GREATER__ than 1

10. Changing Distance
When a machine increases __DISTANCE__, you must apply a greater __INPUT FORCE__
For a machine that __INCREASE__ distance the __OUTPUT__ force is less than the input force.

11. Changing Direction
When a machine changes the __DIRECTION__ of the input force, the amount of force and the distance __REMAINS THE SAME__
If only direction changes, the __INPUT__ force will be the same as the __OUTPUT__force. The M.A. will __ALWAYS__ be 1.

12. Efficiency of Machines
The __EFFICIENCY__ of a machine compares the output work to the input work.
Efficiency is expressed as a __PERCENT__
Calculating Efficiency
Efficiency = __OUTPUT WORK__ / __INPUT WORK__ X __100%__
Real and Ideal Machines
All machines have an __EFFICIENCY__ of __LESS__ than __100%__
100% effieciency is called an __IDEAL MACHINE__