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## Chapter Goal: To introduce the fundamental concepts of motion.

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### Chapter 1 Concepts of Motion Pickup PSE3e Photo from page 2, snowboarder jump. Chapter Goal: To introduce the fundamental concepts of motion. Slide 1-2 – PowerPoint PPT presentation

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Title: Chapter Goal: To introduce the fundamental concepts of motion.

1
Chapter 1 Concepts of Motion
Pickup PSE3e Photo from page 2, snowboarder jump.
• Chapter Goal To introduce the fundamental
concepts of motion.

Slide 1-2
2
Chapter 1 Preview
Slide 1-3
3
Chapter 1 Preview
Slide 1-4
4
• Four basic types of motion

Slide 1-19
5
Making a Motion Diagram
• Consider a movie of a moving object.
• A movie camera takes photographs at a fixed rate
(i.e., 30 photographs every second).
• Each separate photo is called a frame.
• The car is in a different position in each frame.
• Shown are four frames in a filmstrip.

Slide 1-20
6
Making a Motion Diagram
• Cut individual frames of the filmstrip apart.
• Stack them on top of each other.
• This composite photo shows an objects position
at several equally spaced instants of time.
• This is called a motion diagram.

Slide 1-21
7
Examples of Motion Diagrams
• An object that has a single position in a motion
diagram is at rest.
• Example A stationary ball on the ground.
• An object with images that are equally spaced is
moving with constant speed.
• Example A skateboarder rolling down the sidewalk.

Slide 1-22
8
Examples of Motion Diagrams
• An object with images that have increasing
distance between them is speeding up.
• Example A sprinter starting the 100 meter dash.
• An object with images that have decreasing
distance between them is slowing down.
• Example A car stopping for a red light.

Slide 1-23
9
Examples of Motion Diagrams
two dimensions.
• Example A jump shot from center court.
• In this case the ball is slowing down as it
rises, and speeding up as it falls.

Slide 1-24
10
Position and Time
• In a motion diagram it is useful to add numbers
to specify where the object is and when the
object was at that position.
• Shown is the motion diagram of a basketball,
with 0.5 s intervals between frames.
• A coordinate system has been added to show (x,
y).
• The frame at t ? 0 is frame 0, when the ball is
at the origin.
• The balls position in frame 4 can be specified
with coordinates (x4, y4) ? (12 m, 9 m) at time
t4 ? 2.0 s.

Slide 1-31
11
Position as a Vector
• Another way to locate the ball is to draw an
arrow from the origin to the point representing
the ball.
• You can then specify the length and direction of
the arrow.
• This arrow is called the position vector of
the object.
• The position vector is an alternative form of
specifying position.
• It does not tell us anything different than the
coordinates (x, y).

Slide 1-32
12
Slide 1-33
13
Sam is standing 50 ft east of the corner of 12th
Street and Vine. He then walks northeast for 100
ft to a second point. What is Sams change of
position?
• Sams initial position is the vector .
• Vector is his position after he finishes
walking.
• Sam has changed position, and a change in
position is called a displacement.
• His displacement is the vector labeled .

Slide 1-34
14
Definition of Displacement
• The displacement of an object as it moves
from an initial position to a final position
is
• The definition of involves vector
subtraction.
• With numbers, subtraction is the same as the
• Similarly, with vectors

Slide 1-35
15
Tactics Vector Subtraction
Slide 1-36
16
Time Interval
• Its useful to consider a change in time.
• An object may move from an initial position
at time ti to a final position at time tf.

A stopwatch is used to measure a time interval.
• Different observers may choose different
coordinate systems and different clocks, however,
all observers find the same values for the
displacement ? and the time interval ?t.

Slide 1-41
17
Average Speed, Average Velocity
• To quantify an objects fastness or slowness, we
define a ratio
• Average speed does not include information about
direction of motion.
• The average velocity of an object during a time
interval ?t, in which the object undergoes a
displacement ? , is the vector

The victory goes to the runner with the highest
average speed.
Slide 1-42
18
Motion Diagrams with Velocity Vectors
• The velocity vector is in the same direction as
the displacement ? .
• The length of is directly proportional to the
length of ? .
• Consequently, we may label the vectors connecting
the dots on a motion diagram as velocity vectors
.
• Below is a motion diagram for a tortoise racing a
hare.
• The arrows are average velocity vectors.
• The length of each arrow represents the average
speed.

Slide 1-43
19
EXAMPLE 1.2 Accelerating Up a Hill
Motion diagram of a car accelerating up a hill.
Slide 1-44
20
Acceleration
• Sometimes an objects velocity is constant as it
moves.
• More often, an objects velocity changes as it
moves.
• Acceleration describes a change in velocity.
• Consider an object whose velocity changes from
to during the time interval ?t.
• The quantity is the change
in velocity.
• The rate of change of velocity is called the
average acceleration

The Audi TT accelerates from 0 to 60 mph in 6 s.
Slide 1-45
21
Tactics Finding the Acceleration Vector
Slide 1-46
22
Tactics Finding the Acceleration Vector
• Notice that the acceleration vectors goes beside
the dots, not beside the velocity vectors.
• That is because each acceleration vector is the
difference between two velocity vectors on either
side of a dot.

Slide 1-47
23
Speeding Up or Slowing Down?
• When an object is speeding up, the acceleration
and velocity vectors point in the same direction.
• When an object is slowing down, the acceleration
and velocity vectors point in opposite
directions.
• An objects velocity is constant if and only if
its acceleration is zero.
• In the motion diagrams to the right, one object
is speeding up and the other is slowing down,
but they both have acceleration vectors toward
the right.

Slide 1-53
24
Tactics Determining the Sign of the Position,
Velocity, and Acceleration
Slide 1-56
25
Tactics Determining the Sign of the Position,
Velocity, and Acceleration
Slide 1-57
26
Tactics Determining the Sign of the Position,
Velocity, and Acceleration
Slide 1-58
27
Position-versus-Time Graphs
• Below is a motion diagram, made at 1 frame per
minute, of a student walking to school.
• A motion diagram is one way to represent the
students motion.
• Another way is to make a graph of x versus t for
the student

Slide 1-65
28
Example 1.7 Interpreting a Position Graph
Slide 1-66
29
Example 1.7 Interpreting a Position Graph
Slide 1-67
30
Example 1.9 Launching a Weather Rocket
Slide 1-74
31
Example 1.9 Launching a Weather Rocket
Slide 1-75
32
Example 1.9 Launching a Weather Rocket
Slide 1-76
33
Example 1.9 Launching a Weather Rocket
Slide 1-77
34
Units
• Science is based on experimental measurements,
and measurements require units.
• The system of units in science is called le
Système Internationale dunités or SI units.
• The SI unit of time is the second, abbreviated
s.
• 1 s is defined as the time required for
9,192,631,770 oscillations of the radio wave
absorbed by a cesium-133 atom.
• The SI unit of length is the meter, abbreviated
m.
• 1 m is defined as the distance traveled by light
in a vacuum during 1/299,292,458 of a second.

An atomic clock at the National Institute of
Standards and Technology is the primary standard
of time.
Slide 1-78
35
Units
• The SI unit of mass is the kilogram, abbreviated
kg.
• 1 kg is defined as the mass of the international
standard kilogram, a polished platinum-iridium
cylinder stored in Paris.
• Many lengths, times, and masses are either much
less or much greater than the standards of 1 m, 1
s, and 1 kg.
• We use prefixes to denote various powers of 10,
which make it easier to talk about quantities.

Slide 1-79
36
Unit Conversions
• It is important to be able to convert back and
forth between SI units and other units.
• One effective method is to write the conversion
factor as a ratio equal to one.
• Because multiplying by 1 does not change a
value, these ratios are easily used for unit
conversions.
• For example, to convert the length 2.00 feet to
meters, use the ratio
• So that

Slide 1-80
37
Assessment
• When problem solving, it is important to decide
• For example, if you are working a problem about
automobile speeds and reach an answer of 35
m/s, is this a realistic speed?
• The table shows some approximate conversion
factors that can be used to assess answers.
• Using 1 m/s 2 mph, you find that 35 m/s is
roughly 20 mph, a reasonable speed for a car.
• If you reached an answer of 350 m/s, this would
correspond to an unreasonable 700 mph, indicating
that perhaps you made a calculation error.

Slide 1-81
38
Significant Figures
• Its important in science and engineering to
state clearly what you know about a situationno
less, and no more.
• For example, if you report a length as 6.2 m, you
imply that the actual value is between 6.15 m and
6.25 m and has been rounded to 6.2.
• The number 6.2 has two significant figures.
• More precise measurement could give more
significant figures.
• The appropriate number of significant figures is
determined by the data provided.
input value with the smallest number of
significant figures determines the number of
significant figures to use in reporting the
output value.

Slide 1-82
39
Determining significant figures.
Slide 1-83
40
Tactics Using Significant Figures
Slide 1-84
41
EXAMPLE 1.10 Using significant figures
Slide 1-85
42
Orders of Magnitude and Estimating
Some approximate lengths and masses Distance you
can drive in 1 hour 105 m Distance
across a college campus 1000 m Length of
fingernail 0.01 m Thickness of a sheet of paper
104 m Small car 1000 kg Large human 100
kg Science textbook 1 kg Apple 0.1
kg Raisin 103 kg
• In many cases a very rough estimate of a number
is sufficient.
• A one-significant-figure estimate or calculation
is called an order-of-magnitude estimate.
• An order-of-magnitude estimate is indicated by
the symbol , which indicates even less precision
than .

Slide 1-86
43
Chapter 1 Summary Slides
Slide 1-89
44
General Strategy
Slide 1-90
45
General Strategy
Slide 1-91
46
Important Concepts
Slide 1-92
47
Important Concepts
Slide 1-93