Describing and Measuring Motion
Describing and Measuring Motion
How do you recognize motion?
How do you recognize motion?
An object is in
An object is in
motion
motion
when its
when its
distance
distance
from
from
another object is
another object is
changing
changing
Movement depends
Movement depends
on your point of
What is a reference point?
What is a reference point?
A
A
place
place
or object used for
or object used for
comparison to determine if
comparison to determine if
something is in
something is in
motion
motion
An
An
object
object
is in motion if it
is in motion if it
changes
changes
position
position
relative to a
relative to a
reference
Determining When an
Determining When an
Object is in Motion
Object is in Motion
Whether or not an object is in motion
Whether or not an object is in motion
depends
depends
on the
on the
reference point
reference point
you choose & if the
you choose & if the
distance between
distance between
the object and the reference
the object and the reference
point is
point is
changing.
changing.
SWBAT: Investigate, measure and describe what happens to the
SWBAT: Investigate, measure and describe what happens to the
motion, speed ,velocity and acceleration of moving objects
Negative Distance &
Negative Distance &
Football
Football
Question:
Question:
Can a
Can a distance be
distance be negative in
negative in
relationship to a reference point?
relationship to a reference point?
Football Example:
Football Example:
Reference point
Reference point in football
in football
(below),
(below), positive play
positive play (right),
(right),
negative play-
negative
play-sacked for a loss
Which of the following is true if you are riding your bike
Which of the following is true if you are riding your bike
past the middle school?
past the middle school?
A.
A.
You a
You a
re mo
re mo
ving
ving
rel
rel
ativ
ativ
e to t
e to t
he bik
he bik
e, but no
e, but no
t the s
t the s
cho
cho
ol.
ol.
B.
B.
You
You
are
are
not
not
mov
mov
ing
ing
rel
rel
ativ
ativ
e to
e to
the
the
sch
sch
ool
ool
or t
or t
he bi
he bi
ke.
ke.
C.
C.
You a
You a
re mo
re mo
ving
ving
rel
rel
ativ
ativ
e to th
e to th
e sch
e sch
ool
ool
, but no
, but no
t rel
t rel
ativ
ativ
e to th
e to th
e
e
bike.
bike.
D.
What is the basic unit of length?
What is the basic unit of length?
The
The
meter
meter
––a
a
little longer
little longer
than a
What do scientists use to measure the
What do scientists use to measure the
length of an object smaller than a yard?
length of an object smaller than a yard?
A
A
centimeter
centimeter
––one
one
hundredth of a
hundredth of a
meter, so there are
meter, so there are
100
100
centimeters in a
centimeters in a
meter
meter
A
A
millimeter
millimeter
––There
There
are
are
1,000
1,000
millimeters in a
millimeters in a
meter
meter
How do scientists measure long
How do scientists measure long
distances?
distances?
The
The
kilometer
kilometer
–
–
There are
There are
1,000
1,000
meters
meters
in a kilometer
in a kilometer
1mile= 1.6km
1mile= 1.6km
How do scientists calculate speed?
How do scientists calculate speed?
Speed
Speed
––the
the
distance
distance
the object
the object
travels in one unit of
travels in one unit of
time
time
Rate
Rate
––tells you the amount of
tells you the amount of
something
something
that occurs or changes in
that occurs or changes in
one unit of
one unit of
time
time
Speed =
Speed =
distance
distance
time
What is constant speed?
What is constant speed?
If the
If the
speed
speed
of
of
an object does
an object does
not
not
change, the
change, the
object is
object is
traveling at a
traveling at a
constant
What is average speed?
What is average speed?
Most objects do
Most objects do
not
not
move at
move at
constant
constant
speeds
speeds
for very
for very
long
long
To find average
To find average
speed
speed
divide
divide
the
the
total
total
distance
distance
by
by
the total
the total
time
time
•
Calculating Speed
Calculating Speed
How can you calculate How can you calculate speed? speed? If you travel 45 If you travel 45 km in 3 hours, what iskm in 3 hours, what is your average speed?
your average speed?
Speed = change in Speed = change in distance/change in timedistance/change in time
Instant speedInstant speed is your speed at a certain time. is your speed at a certain time.
Average speed Average speed is your averaged speed for the ENTIRE trial, event, or is your averaged speed for the ENTIRE trial, event, or race.
race.
What is Velocity?
What is Velocity?
Speed
Speed
in a given
in a given
direction
direction
When you know the
When you know the
speed
speed
and
and
direction
direction
of an
of an
object
object
’’s motion, you
s motion, you
know the
know the
velocity
velocity
of the
of the
object
object
Example 15 km/hour
Example 15 km/hour
westward
Do Now: What is the sp
Do Now: What is the sp
eed average speed of a car
eed average speed of a car
that traveled 75km/h in 5 hours
that traveled 75km/h in 5 hours
Speed= Distance/ Time
Speed= Distance/ Time
Distance= 75km , Time =5 hours so 75km/5hrs=
Distance= 75km , Time =5 hours so 75km/5hrs=
15km/hr
15km/hr
SWBAT: Investigate, measure and describe what
SWBAT: Investigate, measure and describe what
happens to the motion,
happens to the motion,
speed ,velocity and
speed ,velocity and
acceleration of moving objects
How do you graph motion?
How do you graph motion?
You can show the
You can show the
motion
motion
of an object on
of an object on
a
a
line
line
graph in which
graph in which
you plot
you plot
distance
distance
against
against
time
time
Time
Time
is along the x-
is along the
x-axis and
axis and
distance
distance
on
on
the y-axis
How do you interpret motion
How do you interpret motion
graphs?
graphs?
A
A
straight
straight
line indicates
line indicates
a
a
constant
constant
speed
speed
The
The
steepness
steepness
depends
depends
on how quickly or slowly
on how quickly or slowly
the object is moving
the object is moving
The faster the motion
The faster the motion
the
Distance Determination (from a Speed-Time
Distance Determination (from a Speed-Time
Graph)
Graph)
How far will the object have gone in 2 seconds?
How far will the object have gone in 2 seconds?
10 meters (5 m/s x 2 s)
10 meters (5 m/s x 2 s)
Or
Or
Determine the a
Determine the a
rea under the line:
rea under the line:
Create a recta
Create a recta
ngle and determine
ngle and determine
its area (l x w = 2 s x 5 m/s = 10 m)
its area (l x w = 2 s x 5 m/s = 10 m)
SWBAT: Investigate, measure and describe what happens to
SWBAT: Investigate, measure and describe what happens to
the
the
motion, speed ,velocity and acceleration of moving objects
motion, speed ,velocity and acceleration of moving objects
5 m/s 5 m/s 1 1 s s 2 2 ss
SPEED
SPEED
(m/s)
(m/s)
Time (s)
Time (s)
Graphing Motion (Calculating speed)
Graphing Motion (Calculating speed)
You can show the motion of an object on a line graph in
You can show the motion of an object on a line graph in
which you plot
which you plot
distance versus time
distance versus time
.
.
Remember:
Remember:
Velocity
Velocity
is
is
the
the
change in
change in
distancedistancein a certain direction during a
in a certain direction during a
certain length
Speed vs. Velocity
Speed vs. Velocity
Do Now:
Do Now:
Mark is jogging at 6.0 mph, while Sue
Mark is jogging at 6.0 mph, while Sue
is also jogging at 6.0 mph.
is also jogging at 6.0 mph.
However, Mark
However, Mark
’’s velocity is -6.0 mph while Sue
s velocity is -6.0 mph while Sue
’’s is
s is
6.0 mph.
6.0 mph.
Why are
Why are
their
their
speeds the same, but their velocities are different?
speeds the same, but their velocities are different?
SWBAT: Investigate, measure and describe what happens to
SWBAT: Investigate, measure and describe what happens to
the motion, speed
the motion, speed
,velocity and acceleration of moving objects
,velocity and acceleration of moving objects
Goal:
Goal:
Determine
Determine
the difference
the difference
between SPEED
between SPEED
and VELOCITY.
and VELOCITY.
Speed vs. Velocity Experiment
Speed vs. Velocity Experiment
•
•Were there anyWere there any negative velocitiesnegative velocities? ? Why Why is tis this the his the case?case? Is Is velocityvelocity
just speed?
just speed? If not, what else iIf not, what else is factored in to s factored in to velocity? velocity? Hint-Hint- Think aboutThink about when your velocity was negative relative to the
when your velocity was negative relative to the motion sensor, andmotion sensor, and keep in mind that
keep in mind that speed is NEVER negative.speed is NEVER negative.
Scenario:Scenario: Mark is jogging Mark is jogging at a speed at a speed of 6.0 mof 6.0 mph, while Sue ph, while Sue is alsois also jogging at a speed of
jogging at a speed of 6.0 mph. 6.0 mph. However, Mark However, Mark ’’s velocity is -6.0 mphs velocity is -6.0 mph
while Sue
while Sue’’s is 6.s is 6.0 mph. 0 mph. Why are their Why are their speeds speeds the same, bthe same, but theirut their
velocities are different? velocities are different?
Velocity = speed + Velocity = speed + direction relative to a reference pointdirection relative to a reference point
So, Mark was goingSo, Mark was going just as fast just as fast as Sue, but in the as Sue, but in the opposite direction.opposite direction.
Peregrine Falcons
Peregrine Falcons
can dive at
can dive at
speeds up to 242 mph.
What is Acceleration?
What is Acceleration?
The
The
rate
rate
at which
at which
velocity
velocity
changes
changes
In science,
In science,
acceleration refers
acceleration refers
to:
to:
increasing
increasing
speed
speed
decreasing
decreasing
speed
speed
How do you calculate acceleration?
How do you calculate acceleration?
To determine the acceleration rate of
To determine the acceleration rate of
an object, you must calculate the
an object, you must calculate the
change
change
in velocity during each unit of
in velocity during each unit of
time
time
Acceleration =
Acceleration =
Final velocity
Final velocity
–
–
Starting velocity
Starting velocity
Time
Calculating Acceleration
Calculating Acceleration
What does it What does it mean if a car accelerates? mean if a car accelerates? Have you ever heard oHave you ever heard of a car that can gf a car that can goo 0 to 60 mph
0 to 60 mph in about in about 6 seconds6 seconds? ? (Just (Just like like mine). mine). What What about about when a when a carcar decelerates?
decelerates?
To determine theTo determine the accelerationacceleration of an object moving in a straight line, you must of an object moving in a straight line, you must calculate the
calculate the change in velocity per unit of tchange in velocity per unit of timeime
Average Acceleration = (final velocityAverage Acceleration = (final velocity –– starting velocity)/time starting velocity)/time
Graphing
Graphing
Acceleration
Acceleration
You can use both a
You can use both a speed-versus-
speed-versus-time
time
graph and a
graph and a
distance-versus-time
distance-versus-time graph
graph
to analyze the motion of an
to analyze the motion of an
accelerating
accelerating
object.
object.
-Calculating Acceleration
Calculating Acceleration
As a roller-coaster car starts down a slope, its speed is 4 m/s.
As a roller-coaster car starts down a slope, its speed is 4 m/s.
But 3 seconds later, at the bottom, its speed is 22 m/s. What is
But 3 seconds later, at the bottom, its speed is 22 m/s. What is
its average acceleration?
its average acceleration?
Read and Understand
Read and Understand
What information have you been given?
What information have you been given?
Initial
Initial
speed
speed
=
=
4 m/s
4 m/s
Final
Final
Speed
Speed
=
=
22 m/s
22 m/s
Calculating Acceleration
Calculating Acceleration
As a roller-coaster car starts down a slope, its speed is 4 m/s.
As a roller-coaster car starts down a slope, its speed is 4 m/s.
But 3 seconds later, at the bottom, its speed is 22 m/s. What is
But 3 seconds later, at the bottom, its speed is 22 m/s. What is
its average acceleration?
its average acceleration?
Plan and Solve
Plan and Solve
What quantity are you trying to What quantity are you trying to calculate?calculate?
The The average average acceleration acceleration of of the the roller-coaster roller-coaster car car = = ____
What formula contains the given quantities and the unknownWhat formula contains the given quantities and the unknown quantity?
quantity?
Acceleration = (Acceleration = (Final speedFinal speed – – Initial speedInitial speed)/)/TimeTime
Perform the calculation.Perform the calculation.
Acceleration = (Acceleration = (22 m/s22 m/s – – 4 m/s4 m/s)/)/3 s3 s = 18 m/s/ = 18 m/s/33 ss
Acceleration = 6 m/sAcceleration = 6 m/s22
The roller-coaster car The roller-coaster car ’’s average acceleration is 6 m/ss average acceleration is 6 m/s22..
Calculating Acceleration
Calculating Acceleration
As a roller-coaster car starts down a slope, its speed is
As a roller-coaster car starts down a slope, its speed is
4
4
m/s. But 3 seconds later, at the
m/s. But 3 seconds later, at the
bottom, its speed is 22 m/s.
bottom, its speed is 22 m/s.
What is its
What is its
average acceleration?
average acceleration?
Look Back and Check
Look Back and Check
Does your answer make sense?
Does your answer make sense?
The answer is reasonable. If the car
The answer is reasonable. If the car
’’s speed increases by
s speed increases by
6 m/s each second, its
6 m/s each second, its
speed will be 10
speed will be 10
m/s after 1 second,
m/s after 1 second,
16 m/s after 2 seconds, and
Calculating Acceleration
Calculating Acceleration
Practice Problem
Practice Problem
A certain car brakes from 27 m/s to rest in 9
A certain car brakes from 27 m/s to rest in 9
seconds. Find the car
seconds. Find the car
’’s average acceleration.
s average acceleration.
(0 m/s
(0 m/s
– –27 m/s )
27 m/s )
÷÷9 s =
9 s =
-
-
27 m/s
27 m/s
÷÷9 s =
9 s =
-3 m/s
-3 m/s
22
This is a
This is a
negative acceleration
negative acceleration
,
,
which is also
which is also
called
called
a
a
deceleration (slowing down)
deceleration (slowing down)
