the ability to cause change 1. mechanical energy t y p e s o f e n e r g y 2
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mechanical energy
Types of
Types of
EnergyEnergy
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types of energyo Thermal energy - due to temperature
(recall that this comes from the motion of molecules, so it is really kinetic energy)
o Heat energy -transfer of thermal energy
o Chemical Potential Energy - stored in chemical bonds
o Nuclear energy - stored in the nuclei of an atom
o Electrical energy - EM interactionso Radiant energy -carried by EM waves
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Energy•Energy is the capacity
(ability) to do work. •Kinetic Energy: Associated
with an object in motion•Potential Energy: Present
in an object that has the potential to move because of its position
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CLIP
Kinetic Energy• MotionMotion• KE of an object KE of an object
depends upon two depends upon two variables: variables:
1.1.the mass (m) of the mass (m) of the objectthe object
2.2.the speed (v) of the speed (v) of the object.the object.
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A formula to find the kinetic energy of any body based on its velocity.
Calculating Kinetic Energy
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Potential Energy
•An object An object can store can store energy as energy as the result the result of its of its position.position.
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Forms of potential energy
-position above the Earth’s surface
-stored in something stretchy
-chemical reaction
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Gravitational Potential Energy
• GPE is the energy stored in an object as the result of its vertical position (i.e., height).
• Amt. of GPE is dependent on two variables:1.the mass2.the height
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Calculating Gravitational
Potential Energy
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Elastic Potential
•Elastic PE is the energy stored in elastic materials as the result of their stretching or compressing.
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Conservati
on of
Energy
Conservation of Energy
Energy cannot be created or Energy cannot be created or destroyed…only changed destroyed…only changed from one form to another.from one form to another.
The total energy of an isolated system remains constant (isolated systems have no
external forces and no mass changes)
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14 ENERGY BEFORE =
ENERGY AFTER
Energy can be changed from one form to another, but it does not
disappear.
Mechanical Energy•The motion of some objects
contain a combination of only kinetic and potential energies.
•ME is the sum of the KE and forms PE associated with a system
•Therefore, ME= KE + PE
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TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME
Conservation of Energy
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Conservation of EnergyConservation of Energy
TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME
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Conservation of Mechanical Energy:
Therefore,
MEi = MEf
KEi + PEi = KEf + PEf
½ mvi2 + mghi = ½ mvf
2 + mghf
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Conservation of Mechanical Conservation of Mechanical EnergyEnergy::
•Conservation of ME only hold true when the only energies of the system are KE and PE.
•Therefore, in the presence of friction energy is transformed to other types of energies.
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Energy Conversion
When one type of energy is changed or transformed into
another type of energy
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Can you think of More?
Create a graphic organizer to illustrate energy conversions. draw a picture to represent four
different energy conversion you may encounter in everyday life. Be sure to explain what type of
energy it starts with and what type of energy it ends with.
Examples21
Battery
Lighting a MatchSteam Engine
Energy Conversion
clip
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What about a falling object?
What happens when it hits the ground?
Where did the energy all go?
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•As it is falling and when the object hits the ground the energy is converted into other types of energy such as:
Energy Conversions of a dropped object
•If the object bounces, some energy is converted momentarily into elastic potential energy.
•sound energy (waves), Light Energy (sparks), thermal energy due to friction (heat) in the ground and air, vibrations in the earth (energy waves.)
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If Robin Hood had been Written by an Engineer....
And Robin didst slowly and with great determination put potential energy equal to the work of his muscles into an elastic storage device.
And therewith Robin the Bold and Valiant didst convert this stored energy most quickly, efficiently, and accurately into the velocity of a sturdy and pointed dart (oft called arrow) such that almost all of its former potential energy didst become kinetic. Then this speedy dart didst split an arrow (oft called dart) already buried in most distant
target, having been previously hurled there at an equally great speed by a similar conversion of stored energy.
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EOCT EOCT QuestionsQuestionsWhich statement about energy is
true?A Energy can be increased in a closed system.B Energy cannot be conserved.C Energy can be decreased in a closed system.D Energy cannot be created nor destroyed.
