3rd Quarter Science-SET B

7/21/2019 3rd Quarter Science-SET B

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REVIEWER -3rdQuarter Science-SET B

Force, Motion and Energy7th Grade

What is Energy?

Energy is the ability to do work or cause change.

Examples When the wind mo!es a lea", or picks up a house.#n this case, the change is in the position o" the

ob$ect, so the wind has energy.

Work is done when a F%&'E mo!es an %()E'* some+#*-'E.

When an ob$ect or organism does work on an ob$ect, some o" itsEE&G/ is trans"erred to that ob$ect. o W%&0 could be thought o" as *1E

*&-FE& %F EE&G/. When energy is trans"erred, the ob$ect upon which the workis done G-# energy.

Energy is measured in units called )%23E.

%ne )%23E 4)5 is the amount o" work you do when you exert a "orce o" one EW*%to mo!e an ob$ect a distance o" one ME*E&.

%ne EW*% is the amount o" "orce re6uired to accelerate one kilogram o" mass at

meter per second.

8 kg 9 m:s;

*here are two general kinds o" Energy

0inetic Energy and M- the amount o" matter in anob$ect >=E3%'#*/ speed in a gi!en direction. >


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"orce"ully? /ou would ha!e to exert a greater "orce on thebowling ball because it has a greater mass than the gol" ball.

ince energy is trans"erred during work, the more work you do, the more energy you gi!e to the ball. o, a bowling ball has more

0#E*#' EE&G/ than a gol" ball tra!elling at the same !elocity.

0#E*#' EE&G/ #'&E-E - M- #'&E-E 0#E*#' EE&G/ -3% #'&E-E - =E3%'#*/ #'&E-E

4because you would ha!e to do more work on the bowling ball togi!e it a greater !elocity5

o 0#E*#' EE&G/ depends on both M- -+ =E3%'#*/

*he F%&M23- to calculate 0#E*#' EE&G/ #

0inetic Energy8 Mass 9 =elocity;

;

3ook at the "ormula. +o changes in !elocity and mass ha!e the -ME e@ect on0inetic Energy? o, changing the !elocity will ha!e a greater e@ect on 0inetic

Energy than changing its mass. *his is because !elocity is s6uared.

2se your knowledge o" the game o" (-E(-33 4or any other time when you hitsomething with a stick...5 and gi!e an example o" what weAre talking about in the section abo!e.

4#s it better to hit the baseball with a hea!y bat, or one mo!ing 6uickly?5


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/ou might gi!e this type o" potential energy to an ob$ect when you li"t it.

*he G&-=#*-*#%-3


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also con!erted into the electrical energy your brain uses to think.

%F*E, - EE %F EE&G/ '%=E% -&E EE+E+ *% +% - *-0.

Example

- match trike a match and the mechanical energy needed to mo!e the matchis con!erted to thermal energy. *he thermal energy causes the match to release thestored chemical energy, which is con!erted to thermal energy, and then to theelectromagnetic energy you see as light.

- car engine Electrical energy produces a hot spark. *he thermal energy o" thespark releases the chemical energy o" the "uel. When the "uel burns, the chemicalenergy turns into thermal energy. *hermal energy is con!erted into mechanicalenergy used to m!oe the car, and to electrical energy to produce more sparks

Energy cannot be created %& destroyed, but itcan change "ormB

4*his is much more important than it sounds, tryand remember itB *rust meB5

*1E 3-W %F '%E&=-*#% %F EE&G/D when one energy "orm is con!ertedinto another, % EE&G/ is destroyed in the process. Energy cannot

be created %& destroyed.

EE&G/ -+ F'*#%

-s the pendulum mo!es, it encounters "riction at the pi!ot o" the string and "romthe air through which it mo!es. When an ob$ect experiences "riction, the motion4and thus the kinetic energy5 o" the atoms or molecules increases. *his means the

*1E&M-3 energy increases. o some o" the mechanical energy o" the mo!ingpendulum is con!erted to *1E&M-3 energy. *he pendulum slows down, but noenergy was destroyed.

*1E&M-3 EE&G/ -+ 1E-*

Matter is made o" tiny particles called atoms and molecules. *hese particles arealways in motion, e!en i" the ob$ect they make up isnKt mo!ing at all. ince 0ineticEnergy is the energy o" motion, all particles o" matter ha!e 0#E*#' energy. *he"aster the particles mo!e, the more kinetic energy they ha!e.

L


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*emperature is a measure o" the a!erage 0inetic Energy o" the indi!idual particles inthe ob$ect.

*EM


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1ow is heat trans"erred?*here are three ways that heat can mo!e. 'onduction, 'on!ection and &adiation

'%+2'*#%D #n this process, heat is trans"erred "rom oneparticle o" matter to another particle o" matter without themo!ement o" the matter itsel".

'%=E'*#%D #n this process, heat is trans"erred by themo!ement o" currentswithin a Cuid 4a li6uid or a gas5.

'%=E'*#% '2&&E*D "ormed when hot things rise and

cooler things sink.&-+#-*#%D *his is the trans"er o" energy by electromagneticwa!es. &adiation does not re6uire matter to trans"er the thermalenergy. *his is a big di@erence, and an important one.

#nteresting Factoid...

*hereAs no such thing as cold. 'old is $ust the absence o" heat.

4o, cold doesnAt seep into anything...5

'%+2'*%& -+ #23-*%&

'onductorD a material that conducts heat well.Metals are good conductors o" heat.

#nsulatorD - material that does not conduct heat well.Wood, wool, straw, paper, cork, are all good insulators.

1ouse #nsulation


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3i6uidsD


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!iew.

- &EFE&E'E


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'-3'23-*#G -''E3E&-*#%

-cceleration 8 Final =elocity D #nitial =elocity

Force- F%&'E # -


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- high !elocity also produces a large momentum, e!en when mass is small.Example (ullet shot "rom riCe.

mall kid running "ast into a larger kid.mall "astDmo!ing Ist hitting your chin.

3rd Quarter Science-SET B

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