Chapter 9 Motion and Energy
Table of Contents
Chapter Preview
9.1 Describing Motion
9.2 Speed and Velocity
9.3 Acceleration
9.4 Energy
Chapter 9 Motion and Energy
Chapter Preview Questions
1. Is a moving bus a good reference point from which to
measure your position?
a. No, because it is often late.
b. No, because it is not a stationary object.
c. Yes, because it is very large.
d. Yes, because it can travel very far.
Chapter 9 Motion and Energy
Chapter Preview Questions
1. Is a moving bus a good reference point from which to
measure your position?
a. No, because it is often late.
b. No, because it is not a stationary object.
c. Yes, because it is very large.
d. Yes, because it can travel very far.
Chapter 9 Motion and Energy
Chapter Preview Questions
2. To describe a friend’s position with respect to you, you
need to know
a. Your friend’s distance from you.
b. The direction your friend is facing.
c. Your friend’s distance and direction from you.
d. Your friend’s distance from a nearby object.
Chapter 9 Motion and Energy
Chapter Preview Questions
2. To describe a friend’s position with respect to you, you
need to know
a. Your friend’s distance from you.
b. The direction your friend is facing.
c. Your friend’s distance and direction from you.
d. Your friend’s distance from a nearby object.
Chapter 9 Motion and Energy
Chapter Preview Questions
3. Two cars traveling in the same direction pass you at
exactly the same time. The car that is going faster
a. moves farther in the same amount of time.
b. has more mass.
c. has the louder engine.
d. has less momentum.
Chapter 9 Motion and Energy
Chapter Preview Questions
3. Two cars traveling in the same direction pass you at
exactly the same time. The car that is going faster
a. moves farther in the same amount of time.
b. has more mass.
c. has the louder engine.
d. has less momentum.
Chapter 9 Motion and Energy
Chapter Preview Questions
4. To describe an object’s motion, you need to know its
a. position.
b. change in position.
c. distance.
d. change in position over time.
Chapter 9 Motion and Energy
Chapter Preview Questions
4. To describe an object’s motion, you need to know its
a. position.
b. change in position.
c. distance.
d. change in position over time.
Chapter 9 Motion and Energy
How can you describe an object’s motion?
You are in a stationary car
and another car passes you.
How would you describe the
motion of the other car?
Chapter 9 Motion and Energy
Use Related Words
Word
conclude
Definition
Example Sentence
After investigating the
v. to decide by reasoning evidence, they concluded
that everyone should wear
a bicycle helmet.
Chapter 9 Motion and Energy
Use Related Words
Word
formula
Definition
Example Sentence
n. a series of numbers
and symbols that
represents a
mathematical rule
The formula for the area of
a circle is A = πr2.
Chapter 9 Motion and Energy
Use Related Words
Word
potential
Definition
Example Sentence
adj. the possibility that
something will develop
in a certain way
The student who is studying
chemistry is a potential
chemist.
Chapter 9 Motion and Energy
Apply It!
Choose the word from the table that best completes the sentence.
1.
The
for finding the area of a rectangle is A = l x w.
formula
2. After waiting for 20 minutes, he
that his friend was not coming.
concluded
3. The heavy rains and rising river are a
who live beside the river.
potential
problem for people
Chapter 9 Motion and Energy
End of Chapter
Preview
Chapter 9 Motion and Energy
Section 1:
Describing Motion
When is an object in motion?
What is the difference between distance
and displacement?
Chapter 9 Motion and Energy - Describing Motion
Relative Motion
Whether or not an
object is in motion
depends on the
reference point you
choose.
Chapter 9 Motion and Energy
Distance and Displacement
Distance is the total length of the actual path between two
points. Displacement is the length and direction of a straight
line between starting and ending points.
Chapter 9 Motion and Energy
End of Section:
Describing Motion
Chapter 9 Motion and Energy
Section 2:
Speed and Velocity
When is an object in motion?
What is the difference between distance
and displacement?
Chapter 9 Motion and Energy
Calculating Speed
If you know the distance an object travels in a certain amount
of time, you can calculate the speed of the object.
Chapter 9 Motion and Energy
Graphing Motion
You can use distance-versus-time graphs to interpret motion.
Chapter 9 Motion and Energy
Graphing Motion Activity
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access Active Art about graphing motion.
Chapter 9 Motion and Energy
Velocity
Click the Video button to watch a movie about velocity.
Chapter 9 Motion and Energy
End of Section:
Speed and Velocity
Chapter 9 Motion and Energy
Section 3:
Acceleration
What kind of motion does acceleration refer to?
How do you calculate acceleration?
What graphs can be used to analyze the motion
of an accelerating object?
Chapter 9 Motion and Energy
Calculating Acceleration
To determine the acceleration of an object, you must
calculate its change in velocity per unit of time.
Chapter 9 Motion and Energy
Calculating Acceleration
As a roller-coaster car starts down a slope, its velocity is 4 m/s. But
3 seconds later, its velocity is 22 m/s in the same direction. What is
its acceleration?
Read and Understand
What information have you been given?
Initial velocity = 4 m/s
Final velocity = 22 m/s
Time = 3 s
Chapter 9 Motion and Energy
Calculating Acceleration
As a roller-coaster car starts down a slope, its velocity is 4 m/s. But
3 seconds later, its velocity is 22 m/s in the same direction. What is
its acceleration?
Plan and Solve
What quantity are you trying to calculate?
The acceleration of the roller-coaster car = __
What formula contains the given quantities and the unknown
quantity?
Acceleration = (Final velocity - Initial velocity)/Time
Perform the calculation.
Acceleration = (22 m/s - 4 m/s)/3 s = 18 m/s/3 s
Acceleration = 6 m/s2
The acceleration is 6 m/s2 down the slope .
Chapter 9 Motion and Energy
Calculating Acceleration
As a roller-coaster car starts down a slope, its velocity is 4 m/s. But
3 seconds later, its velocity is 22 m/s in the same direction. What is
its acceleration?
Look Back and Check
Does your answer make sense?
The answer is reasonable. If the car’s velocity increases by 6 m/s
each second, its velocity will be 10 m/s after 1 second, 16 m/s after
2 seconds, and 22 m/s after 3 seconds.
Chapter 9 Motion and Energy
Calculating Acceleration
Practice Problem
A falling raindrop accelerates from 10 m/s to 30 m/s in 2
seconds. What is the raindrop’s acceleration?
(30 m/s - 10 m/s) ÷ 2 seconds = 10 m/s2
Chapter 9 Motion and Energy
Calculating Acceleration
Practice Problem
A certain car can accelerate from rest to 27 m/s in 9
seconds. Find the car’s acceleration.
(27 m/s - 0 m/s) ÷ 9 s = 27 m/s ÷ 9 s = 3 m/s2
Chapter 9 Motion and Energy
Graphing Acceleration
You can use both a speed-versus-time graph and a distanceversus-time graph to analyze the motion of an accelerating
object.
Chapter 9 Motion and Energy
Links on Acceleration
Click the SciLinks button for links on acceleration.
Chapter 9 Motion and Energy
End of Section:
Acceleration
Chapter 9 Motion and Energy
Section 4:
Energy
What factors affect an object’s kinetic energy and
potential energy?
How can kinetic energy and potential energy be
transformed?
What is the law of conservation of energy?
Chapter 9 Motion and Energy
Exponents
An exponent tells how many times a number is used as a factor. For
example, 3 x 3 can be written as 32. You read this number as “three
squared.” In the formula for kinetic energy, speed is squared. For
example, you can calculate the kinetic energy of a 70-kg person moving at
a speed of 2 m/s by using the formula below.
KE = ½ x Mass x Speed2
= ½ x 70 kg x (2 m/s) 2
= 140 kg•m2/s2 or 140 joules.
Note:
1 kg•m2/s2 = 1 joule
Chapter 9 Motion and Energy
Exponents
Practice Problem
What is the kinetic energy of a 30-kg rock moving at a speed
of 10 m/s?
1,500 joules
Chapter 9 Motion and Energy
Kinetic Energy
Kinetic energy increases as mass and speed increase.
Chapter 9 Motion and Energy
Potential Energy
Gravitational potential energy increases as weight and height
increase.
Chapter 9 Motion and Energy
Transformations Between
Potential and Kinetic Energy
A pendulum continuously transforms energy from kinetic to
potential energy and back.
Chapter 9 Motion and Energy
Energy Transformations Activity
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access Active Art about energy transformations.
Chapter 9 Motion and Energy
Links on Energy
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Chapter 9 Motion and Energy
Links on Forms of Energy
Click the SciLinks button for links on forms of energy.
Chapter 9 Motion and Energy
End of Section:
Energy
Chapter 9 Motion and Energy
QuickTake Quiz
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