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Transcript
Energy
The ability to do work or cause
change
Kinetic Energy (KE)


Energy of motion
Affected by mass and velocity
Potential Energy (PE)


Stored energy/has the potential to do
work or cause change
Examples of stored energy from the sun


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Food
Wood
Fossil fuels
Energy of position


Gravitational potential energy
Elastic potential energy
Law of Conservation of Mass
and Energy

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Energy cannot be created or destroyed
Energy can change form


KE ↔ PE
Where did the energy go????
Work and Power

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Work is changing the energy of an
object
Work is done on an object when the
object moves in the same direction as
the force applied
Work = Force X distance
Joule = Newton X meter
Examples:

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Power is the rate at which work is
done
Power = Work ÷ Time
Watt = Joules per second
Horsepower =
Machines
A machine is a tool that makes work
easier



Work in = Work out
Machines do not change the amount of
work done
Machines make work easier
by…….
Changing the direction of the force
applied
1.
Changing the size of the force applied
2.


Less force, longer distance
More force, shorter distance
Simple Machines

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Lever
Inclined plane
Wedge
Screw
Wheel and Axle
Pulley
Lawn mower interactive
Forms of Energy
Mechanical
Thermal
Chemical
Electricity
Electromagnetic
Nuclear
Energy Transformations

A change from one form of energy into
another


Single or multiple transformations
Examples:




Toaster
Cell phone
Running a road race
Power Play
Thermal Energy, Heat
and Temperature
Thermal Energy – the total amount of
internal energy for all the atoms of a
substance
 Temperature – the average moving
energy of the atoms of a substance
 Heat – the thermal energy that is
transferred between objects that have
different temperatures
(high concentration to low concentration)

Temperature Scales (degrees)
Fahrenheit
Celsius
Kelvin
Heat Transfer

Conduction – movement of heat from
one particle of matter to another

Good conductors:

Poor conductors:

Convection – movement of heat by the
circulation of fluid currents


Warm air/water is less dense – Why?
Cold air/water is more dense – Why?

Radiation – movement of heat by
infrared (electromagnetic) waves

Radiation can move through space or
matter
All objects can radiate heat

Heat transfer inter-actives

Insulation


A substance that slows down or
prevents the transfer of heat
Example: Thermos
Specific Heat


The amount of energy needed to raise
the temperature of 1 gram of a
substance 1º C
Every pure substance has a different
specific heat
calorie



The amount of energy needed to raise
the temperature of 1 gram of water by
1º C
1 Calorie = 1000 calories
Calorimeter measures the amount of
heat given off when a substance burns
Food Energy


How does energy get into the food we
eat?
How do we get the energy out of food?