Transcript Slide 1

Ch #
9
Notes
Work, Power, and Machines
Chapter 9.1 Notes
• 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
• Mechanical advantage- (MA) a quantity that
measures how much a machine multiplies
force or distance
Mech Ad = Output force / Input force
Input distance / output distance
Chapter 9.2 notes
• Simple machines- one of the six basic
types of machines of which all other
machines are composed of.
The six simple machines
1. Lever
2. Pulley
3. Wheel and axle
4. Inclined plane
5. Wedge
6. Screw
6 simple machines
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.
Chapter 9.3 Notes
• Potential energy- 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
• Kinetic energy- 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
• Mechanical energy- is the sum of the
kinetic and potential energy of a large
scale system
Chapter 9.4 Notes
• 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
Top of hill has
the greatest
amount of PE
Work Cited
• “Six Simple Machines”. April 14, 2008.
http://www.coolschool.ca/lor/SC9/unit16/U
16L04/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