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Chapter 3 Matter and Energy
3.4
Energy
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Energy
Energy
• Makes objects move.
• Makes things stop.
• Is needed to “do work”.
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Work
Work is done when
• You climb.
• You lift a bag of
groceries.
• You ride a bicycle.
• You breathe.
• Your heart pumps
blood.
• Water goes over a
dam.
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Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Potential Energy
Potential energy is
energy stored for use at
a later time.
Examples are
• Water behind a dam.
• A compressed spring.
• Chemical bonds in
gasoline, coal, or
food.
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Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Kinetic Energy
Kinetic energy is the
energy of matter in
motion.
Examples are
• Swimming.
• Water flowing over a
dam.
• Working out.
• Burning gasoline.
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Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Learning Check
Identify the energy as 1) potential or 2) kinetic.
A.
B.
C.
D.
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Roller blading.
A peanut butter and jelly sandwich.
Mowing the lawn.
Gasoline in the gas tank.
Solution
Identify the energy as 1) potential or 2) kinetic
A. Roller blading. (2 kinetic)
B. A peanut butter and jelly sandwich.
(1 potential)
C. Mowing the lawn. (2 kinetic)
D. Gasoline in the gas tank. (1 potential)
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Forms of Energy
Energy can take many forms.
• Heat
• Mechanical
• Light
• Electrical
• Chemical
• Nuclear
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Changes in Forms of Energy
Energy can change from one form to
another.
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Units for Measuring Energy
or Heat
Heat is measured in joules or calories.
• 4.184 Joules (J) = 1 calorie (cal) (exact)
• 1 kJ = 1000 J
• 1 kilocalorie (kcal) = 1000 calories (cal)
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Examples of Energy In
Joules
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Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Learning Check
How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
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Solution
How many calories are obtained from a pat of
butter if it provides 150 J of energy when
metabolized?
Given:
Plan:
Equality:
Set Up:
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150 J
Need: calories
J
cal
1 cal = 4.184 J
150 J x 1 cal = 36 cal
4.184 J