7th Grade Physical Science-Energy
Transcript of 7th Grade Physical Science-Energy
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A construction worker uses a boardand log as a lever to lift a heavyrock. If the input length(eort) is 3meters and the output length(resistance) is 0.! meters" what isthe ideal mechanical advantage of
the lever# I$A% d&' d% 3m'0.!m%
*+,A- /escribe how ener work
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ys ca
Science
Energy &
Power
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The Nature of Energy Energy the ability to do work or cause a
change. work is the transfer of energy SI unit for energy is Joules the same as Work
Two main types of energy: Kinetic and
Potential Kinetic Energy: the energy of motion Potential Energy: Energy stored for use at a later
time
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Calculating KineticEnergy Kinetic Energy: the energy of motion The amount of kinetic energy depends on the objects mass
and velocity nergy is transferred during work
The more work one does on an object
The more energy one imparts on the object
Kinetic energy !ass " #elocity$
$
%hen mass is doubled& Kinetic Energy is doubled
%hen velocity is doubled& Kinetic Energy is
'uadru(led))
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Whats the KineticEnergy?
%hat is the Kinetic Energy *in +oules, of anob-ect with a mass of / kg and a velocity of /m0s1
%hen mass is doubled& Kinetic Energy isdoubled
%hen velocity is doubled& Kinetic Energy is'uadru(led))
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/o 1ow2 A car is moving with the velocity of 0 m'sand is having mass of 4!0 5g. 6alculate its 5ineticenergy#
$ass of the body m % 4!0 5g" 7elocity v % 0
m's"
5inetic energy is given by 5.& % 4 mv4% 4 8 4!05g (0 m's)4 % 4!00 9oules
5& % 4!0 kg : 04% 4!000'4 %4!009
5&% $74' 4% 9oules
*+,A- /escribe how energy" workand ower are related name and
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Potential Energy: nergystored for use at a later time
! Types: lastic "otential nergy:
nergy stored in springs# bow and arrow# stretched elasticor rubber bands$
%ssociated w& objects that can be stretched or compressed$
'ra(itational "otential nergy: 2eight and weight de(endant *notice its weight3 N4T
mass), 5PE work done to lift and ob-ect to a height 5PE %eight " 2eight )remember that weight * mass + ,$-
m&s!. 5PE mass " 6.7 m0s$ " 2eight
GPE = 100 N x 300 m = 30000 Nm =30000 !o"les
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8i9erent orms ofEnergy ; di9erent ty(es2
!echanical Thermal Energy Chemical Energy
Electrical Energy Electromagnetic Energy Nuclear Energy
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!echanical Energy %ssociated w& the motion )kinetic. or position of an object
)potential. Kinetic Energy exists whene#er an o$%ect which has
mass is in motion with some #elocity E#erything yo"see mo#ing a$o"t has 'inetic energy
Potential Energy exists whene#er an o$%ect which has
mass has a (osition within a )orce *el+ ,he moste#ery+ay exam(le o) this is the (osition o) o$%ects inthe earth-s gra#itational *el+
5PE %eight
"2eight
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Thermal Energy
%ssociated w& the total energy of the particles)atoms and molecules. in an object$ %s thermalenergy increases# the particles increase in speedand the thermal energy )temperature. of theobject increases$
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Chemical Energy
the energy stored in chemical bonds$The potential energy stored incompounds$
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Electrical Energy /o(ing electrical charges$ lectricity
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/o 1ow2 9ohn picked up a bowlingball that was 0 kgs" he lifted it upto his chest which was .! meter
from the ground and he threw itdown the alley at ;m's what is the5inetic energy# +hat was the
potential energy#
*+,A- *tate the law of
conservation of energy
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Electromagneticenergy Tra(els in wa(es# associated w& light# infrared# ultra(iolet#
microwa(es# +1rays# etc 2onger wa(elength yields low fre3uency 4 low energy Shorter wa(elength yield high fre3uency 4 high energy
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Nuclear Energy %ssociated w& the fusion or 5ssion of nuclear
atoms$
-he fusion ofhydrogen intohelium fuels
the power ofthe sun
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Energy Conversion andConservation /ost forms of energy can be converted from one ty(e
to another.
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nergyConversio
n
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Power "ower: the rate at which work is done
"ower * work & time and since: Work * force + distance$
"ower * 7orce + 8istance
Time SI 9nit for "ower is the Watt Watt * Joule & Second ;orsepower : %n %merican unit of power
The amount of work a horse does when it lifts
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Power
Pro$lems
+ % > : /? % > : / ' - ? % 3! 1 : 0 m ' ! sec ? % 3!0 9 ' !
sec % 0 9'sec ? % 0 +atts
W = P x , con#ert 1 ho"r into secon+s. 1ho"r /0 min x /0 sec
1 hr 1 min
Wor' = /0 watts x 3/00 sec =1/000 !o"les = 1/ Kilo%o"les
SWBAT- Create an incline plane using a computer program that will allow to calculate kinetic and
potential energy. And they will use a worksheet to collect data from the simulation and use it to
better understand the factors that contribute to an objects potential and kinetic energy.
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/ue $onday the 4thread ; !0answer all of and [email protected] pg.!;3 and answer " 4 and 3 on pg.;3
&nergy *kate ?ark 6alculatingkinetic and
http2''phet.colorado.edu'en'contribut
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http://phet.colorado.edu/en/contributions/view/3749http://phet.colorado.edu/en/contributions/view/3749http://phet.colorado.edu/en/contributions/view/3749http://phet.colorado.edu/en/contributions/view/3749http://phet.colorado.edu/en/contributions/view/3749http://phet.colorado.edu/en/contributions/view/3749