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CHAPTER
NEW CHAPTER
Work and Energy
the BIG idea
Energy is transferred when a force moves an object.
4.1 Work is the use of force to move an object.
4.2 Energy is transferred when work is done.
4.3 Power is the rate at which work is done.
CHAPTER OUTLINE
4.1
CHAPTER HOME
KEY CONCEPT
Work is the use of force to move an object.
Work is done by a force that acts in the same
direction as the motion of an object.
Work = Force • distance
VOCABULARY
work
joule
applied force
part of force
not doing work
applied force
object
direction of motion
part of force object
doing work
direction of motion
SECTION
OUTLINE
4.2
CHAPTER HOME
KEY CONCEPT
Energy is transferred when work is done.
The amounts of potential energy and kinetic
energy in a system or process may vary, but the
total amount of energy remains unchanged.
GPE = mgh
1 mv2
KE =
2
ME = PE + KE
1
potential energy
kinetic energy
mechanical energy
Top of Ramp
At the top of the ramp, the
skater’s mechanical energy is
equal to her potential energy
because she has no velocity.
VOCABULARY
100%
PE
conservation of
energy
SECTION
OUTLINE
4.2
CHAPTER HOME
KEY CONCEPT
Energy is transferred when work is done.
The amounts of potential energy and kinetic
energy in a system or process may vary, but the
total amount of energy remains unchanged.
GPE = mgh
1 mv2
KE =
2
ME = PE + KE
2
Halfway Down Ramp
As the skater goes down the
ramp, she loses height but gains
speed. The potential energy she
loses is equal to the kinetic
energy she gains.
50% 50%
PE KE
VOCABULARY
potential energy
kinetic energy
mechanical energy
conservation of
energy
SECTION
OUTLINE
4.2
CHAPTER HOME
KEY CONCEPT
Energy is transferred when work is done.
The amounts of potential energy and kinetic
energy in a system or process may vary, but the
total amount of energy remains unchanged.
GPE = mgh
1 mv2
KE =
2
ME = PE + KE
3
potential energy
kinetic energy
mechanical energy
Bottom of Ramp
As the skater speeds along the
bottom of the ramp, all of the
potential energy has changed to
kinetic energy. Her mechanical
energy remains unchanged.
VOCABULARY
100%
KE
conservation of
energy
SECTION
OUTLINE
4.3
KEY CONCEPT
CHAPTER HOME
Power is the rate at which work is done.
Power can be calculated from work and time.
Power = Work
time
VOCABULARY
power
watt
horsepower
Power can be calculated from energy and time.
Power = Energy
time
Power is measured in watts (W) and sometimes
horsepower (hp).
SECTION
OUTLINE
4.1
CHAPTER HOME
KEY CONCEPT
Work is the use of force to move an object.
I. Work is the use of force to move an object.
A. Force is necessary to do work.
VOCABULARY
work
joule
1. Force, Motion, and Work
2. Calculating Work
B. Objects that are moving can do work.
KEY CONCEPT
SUMMARY
4.2
KEY CONCEPT
CHAPTER HOME
Energy is transferred when work is done.
II. Energy is transferred when work is done.
A. Work transfers energy.
B. Work changes potential and kinetic energy.
1. Calculating Gravitational Potential Energy
2. Calculating Kinetic Energy
VOCABULARY
potential energy
kinetic energy
mechanical energy
conservation of
energy
3. Calculating Mechanical Energy
C. The total amount of energy is constant.
1. Conserving Mechanical Energy
2. Losing Mechanical Energy
3. Forms of Energy
KEY CONCEPT
SUMMARY
4.3
KEY CONCEPT
CHAPTER HOME
Power is the rate at which work is done.
III. Power is the rate at which work is done.
A. Power can be calculated from work and time.
1. Calculating Power from Work
VOCABULARY
power
watt
horsepower
2. Horsepower
B. Power can be calculated from energy and time.
1. Calculating Power from Energy
2. Everyday Power
KEY CONCEPT
SUMMARY