Chapter 1: Motion
Section 1: Describing and Measuring Motion
How do you recognize motion?
Chapter 1: Motion
Section 1: Describing and Measuring Motion
How do you recognize motion?
 An
object is in
motion when its
distance from
another object is
changing
Chapter 1: Motion
Section 1: Describing and Measuring Motion
How do you recognize motion?
Movement
depends on your
point of view
Frame of reference
What is a reference point?
Frame of Reference
A
place or object used for
comparison to determine if
something is in motion
 An object is in motion if it
changes position relative to a
reference point
What is the basic unit of length?
 The
meter – a little longer than
a yard
What do scientists use to measure the length
of an object smaller than a yard?
A
centimeter – one
hundredth of a meter,
so there are 100
centimeters in a
meter
 A millimeter – There
are 1,000 millimeters
in a meter
How do scientists measure long
distances?
 The
kilometer
– There are
1,000 meters
in 1 kilometer
How do scientists calculate speed?
 Speed
– the distance the object
travels in one unit of time
Rate – tells you the amount of
something that occurs or
changes in one unit of time
Speed = distance
time
What is constant speed?
 If
the speed of
an object does
not change, the
object is traveling
at a constant
speed
What is average speed?
 Most
objects do
not move at
constant speeds
for very long
 To find average
speed divide the
total distance by
the total time
•Car trip
What is Velocity?
 Speed in a given
direction
 When you know the
speed and direction of
an object’s motion, you
know the velocity of the
object
 Example: 15 km/hour
westward
How do you graph motion?
 You
can show the
motion of an object
on a line graph in
which you plot
distance against
time
 Time is along the xaxis and distance on
the y-axis
How do you interpret motion graphs?
A
straight line indicates
a constant speed
 The steepness depends
on how quickly or slowly
the object is moving
The faster the motion
the steeper the slope
Section 2: Slow motion on Planet
Earth
 According
to their
explanation, known
as the theory of
plate tectonics,
Earth’s plates move
ever so slowly in
various directions
How fast do plates move?
 Some
small plates
can move as much
as several
centimeters per
year, whereas other
move only a few
millimeters per
year
How can you calculate the distance
an object has moved?
 Rearrange
the speed formula
Distance = Speed x Time
 Converting units – choose a
conversion factor that will allow you
to cancel units
D
S
T
Section 3: Acceleration
What is Acceleration?
 The
rate at which
velocity changes
 In science,
acceleration refers to:
increasing speed
decreasing speed
changing direction
Acceleration
 Whenever an objects speed
increases, the object
accelerates.
Pitcher throwing a softball
Car moving from a stopped
position
Acceleration
 Whenever an objects speed
SLOWS DOWN, the object
decelerates or has negative
acceleration.
Softball landing in the catcher’s
glove.
Car stopping at a red light.
Acceleration
 Acceleration
can be a change in
direction as well as a change in
speed.
 Runners
accelerate as the round a curve
 car accelerates as it follows a curve in
the road
 a softball accelerates as it is hit by a
bat.
Acceleration
 Many
objects continuously change
direction without changing speed.
 Circular
motion – a motion along
a circular path.
Ex. Seats on a Ferris wheel
Stop and Think

How can a car be accelerating if its speed
is constant at 65 km/hr?
How do you calculate acceleration?
 To
determine the acceleration rate of an
object, you must calculate the change
in velocity during each unit of time
 Acceleration = Final velocity – Initial velocity
Time
How do you interpret graphs to
determine acceleration?
Acceleration vs. Constant speed

The acceleration at any moment is equal
to the slope of the velocity time graph at
that moment in time