Question

Section 15.2 Energy Conversion
and Conservation
(pages 453–459)
This section describes how energy is converted from one form to another and
presents the law of conservation of energy.
Reading Strategy (page 453)
Relating Cause and Effect As you read, complete the flowchart to explain
an energy conversion used by some gulls to obtain food. For more
information on this Reading Strategy, see the Reading and Study Skills in
the Skills and Reference Handbook at the end of your textbook.
How Gulls Use Energy Conversions
Energy Conversion (page 454)
1. Is the following sentence true or false? Energy can be converted from one
form to another.
2. When a wind-up toy is set in motion, elastic potential energy that was
stored in a compressed spring is converted into the
of the toy’s moving parts.
Conservation of Energy (page 455)
3. What does the law of conservation of energy state?
4. A moving object slows down because friction causes a continual
conversion of kinetic energy into . Circle the
correct answer.
mechanical potential thermal
energy energy energy
Physical Science Reading and Study Workbook Level B ■ Chapter 15 175
© by Savvas Learning Company LLC. publishing as Savvas Prentice Hall. All rights reserved.
Gull lifts oyster,
increasing
oyster’s
gravitational
potential energy.



Energy Conversions (pages 456–458)
5. As an object falls, the gravitational potential energy of the object is
converted into .
6. At what point during a pole-vaulter’s jump is his gravitational
potential energy the greatest? Circle the letter of the correct answer.
a. when he leaves the ground
b. at his greatest height
c. when he hits the ground
7. Circle the letter of the type of energy that increases as the pole bends
before it propels a pole-vaulter up into the air.
a. kinetic energy
b. mechanical energy
c. elastic potential energy
8. Is the following sentence true or false? For a mechanical change in an
isolated system, the mechanical energy at the beginning equals the
mechanical energy at the end of the process, as long as friction is
negligible.
9. Tell whether the following situations illustrate kinetic energy, potential energy,
or both.
What Type of Energy Is It?
Situation Form of Energy
A stationary wind-up toy with a compressed spring
A descending roller coaster car
A skier poised to take off at the top of a hill
A car driving on a flat road
A vibrating guitar string
Energy and Mass (page 459)
10. Circle the letters of each correct sentence. What does Einstein’s equation
imply about mass and energy?
a. Mass and energy are equivalent.
b. Mass and energy are never created.
c. Mass and energy can be converted to each other.

Answer 1

How Gulls Use Energy Conversions (flowchart summary)
- Gull lifts oyster → oyster’s gravitational potential energy increases.
- Gull drops oyster → gravitational potential energy converts to kinetic energy as the oyster falls.
- Oyster strikes rocks → kinetic energy is converted into mechanical energy of breaking (and some thermal and sound energy).
- Oyster opens/breaks → gull eats the food.

Energy Conversion
1. True — energy can be converted from one form to another.

2. kinetic energy

Conservation of Energy
3. The law of conservation of energy states that energy cannot be created or destroyed — it can only be transformed from one form to another; the total energy of an isolated system remains constant.

4. thermal energy

Energy Conversions
5. kinetic energy

6. b. at his greatest height

7. c. elastic potential energy

8. True — for a mechanical change in an isolated system (with negligible friction), mechanical energy at the beginning equals mechanical energy at the end.

9. What Type of Energy Is It?
- A stationary wind-up toy with a compressed spring: potential energy (elastic potential)
- A descending roller coaster car: both (gravitational potential and kinetic)
- A skier poised to take off at the top of a hill: potential energy (gravitational)
- A car driving on a flat road: kinetic energy
- A vibrating guitar string: both (kinetic and elastic potential)

Energy and Mass
10. a and c are correct.
- a. Mass and energy are equivalent. (true)
- b. Mass and energy are never created. (not a correct implication of Einstein’s equation as stated)
- c. Mass and energy can be converted to each other. (true)