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CHAPTER 4 ENERGY, WORK, HEAT, AND POWER
Try This Activity: Analyzing a Toy’s Action
(Page 123)
(a) Answers may vary. Spinning the toy clockwise gives it kinetic energy. This energy transforms into gravitational potential
energy and back into kinetic energy as the motion changes to rocking. The rocking motion becomes counterclockwise
rotation because of the asymmetric shape of the curved side. (A more detailed explanation for teacher reference is given
in the introduction to this activity. Students are not expected to give such detail until they have completed section 4.4.)
(b) Any reasonable answer is acceptable. For example, the original energy of motion changes to energy of position, which
changes back to energy of motion. Some of the original energy of motion goes to overcoming friction.
4.1 ENERGY AND ENERGY TRANSFORMATIONS
PRACTICE
(Pages 125–126)
Understanding Concepts
1. Examples of energy use today that would not have been available two generations ago are nuclear potential energy
harnessed by nuclear power reactors, chemical potential energy harnessed by fuel cells, and radiant solar energy
harnessed by photovoltaic cells.
2. (a) A bonfire produces radiant energy.
(b) A moving baseball has kinetic energy.
(c) A solar collector heats water through thermal energy.
(d) A stretched rubber band possesses elastic potential energy.
(e) A siren emits sound energy.
3. (a) The explosion of fireworks is the conversion of chemical potential energy into sound, thermal, kinetic, and radiant
energy.
(b) The arrow leaving the bow has kinetic energy, having been converted from elastic potential energy.
(c) The thermal energy being emitted by a hot driveway has come from radiant solar energy.
(d) The gain in gravitational potential energy and kinetic energy of the axe as it rises into the air has been produced by the
conversion of chemical potential energy in the food and oxygen consumed by the camper.
(e) The lawn mower converts chemical potential energy in the gasoline to the kinetic energy of the spinning blade.
4. The music that is produced by a stereo has come from the kinetic energy of the moving speaker, which has been produced
by electrical potential energy that is driving the speaker. The electrical potential energy has been produced by a variety of
energy forms in electrical generating stations.
Section 4.1 Questions
(Page 126)
Understanding Concepts
1. (a)
(b)
(c)
(d)
(e)
2. (a)
(b)
(c)
(d)
Chemical potential energy in the fuel is converted into thermal energy in the hot dog.
Chemical potential energy in the truck’s fuel is converted into mechanical energy of the moving truck.
Chemical potential energy in the food consumed by the child is converted into mechanical energy of the jumping child.
Mechanical energy in the wind is converted into mechanical energy of the moving tree.
Electrical potential energy is converted into thermal energy and light energy (radiant energy) in the light bulb.
An electric baseboard heater warms a room.
A falling glass shatters as it hits the floor.
A chemical heat pack is used to warm a skier’s hands.
An electric motor begins to spin once it is turned on.
Copyright © 2002 Nelson Thomson Learning
Chapter 4 Energy, Work, Heat, and Power
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