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Ch # 9 Notes

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Ch # 9 Notes

Work, Power, and Machines

- Work- quantity of energy transferred by a force when it is applied to a body and causes that body to move in the direction of the force. Has to move!!!
Work = Force x Distance

Work done is measured Joules (J)

- Power- a quantity that measures the rate at which work is done
Power = Work/time

Power is often measured in watts but horsepower is also a unit of power

- Mechanicaladvantage- (MA) a quantity that measures how much a machine multiplies force or distance
Mech Ad = Output force / Input force

Input distance / output distance

- Simplemachines- one of the six basic types of machines of which all other machines are composed of.
The six simple machines

- Lever
- Pulley
- Wheel and axle
- Inclined plane
- Wedge
- Screw

Wheel and Axle

- Compound machine- is a machine made of more than one simple machines.
- A bike and a car are examples of compound machines.

- Potentialenergy- the stored energy resulting from the relative position of objects in a system.
Gravitational potential energy equation

gPE = mass x free-fall acceleration x height

PE = mgh

So the higher up or the bigger the mass the more PE

- Kineticenergy- the energy of a moving object due to its motion
Kinetic energy equation

KE = ½ x mass x velocity squared

KE = ½ mv2

So the faster an object moves the greater the KE

- Mechanicalenergy- is the sum of the kinetic and potential energy of a large scale system

Top of hill has the greatest amount of PE

- The law of conservation of energy states that energy cannot be created or destroyed.
- Energy changes from potential energy to kinetic energy.

Bottom of hill has the greatest amount of KE

- “Six Simple Machines”. April 14, 2008. http://www.coolschool.ca/lor/SC9/unit16/U16L04/SimpleMachinesImages.jpg
- “Wheel and Axle”. April 16, 2008. http://www.ed.uri.edu/SMART96/ELEMSC/SMARTmachines/images/logo.gif
- “Roller Coaster”. April 17, 2008. http://z.about.com/d/travelwithkids/1/0/w/C/coaster_330.JPG