Physical Science
Motion
1.
2.
3.
4.
What is motion?
Do all objects fall at the same rate?
Why do apples fall to earth?
Why doesn’t the moon fall to earth?
How is distance different from
displacement?
 Can they be the same? Explain.

Distance and Displacement
Are You Moving ?


You are sitting down, reading a book….
Are you moving?
Motion Definition

An object is in motion when its
distance from another object is
changing.
Relative Motion
Relative motion is movement in relation to
a REFERENCE POINT.
 This is called Frame of Reference.
 Motion depends on the “Frame of
Reference”
 Therefore an object is in motion if it
changes position relative to a reference
point.

Frame of Reference Example
Look at the figures. In fig.1, the car is to the right of the tree. In fig.2, after 2
seconds, the car is to the left of the tree. As the tree does not move, the car must
have moved from one place to another. Therefore, here the tree is considered as
the frame of reference
Distance vs. Displacement

Distance is the length of a path between
two points.
– SI unit?
 Meters!!
Displacement is the direction from the
starting point and the length of a straight
line from the starting point to the ending
point.
 Sometimes it is the same as distance, but
many times it is not.

Distance vs. Displacement
Animation

http://www.tutorvista.com/content/physic
s/physics-i/motion/difference-distancedisplacement.php

Another example!

http://www.youtube.com/watch?v=Q9D0Y
leyflc (Tutorial)
Scalar Quantities

Show magnitude only (magnitude can be
size, length, or amount)
– Examples: Speed, time, temperature, distance
Vector Quantities

Show magnitude and direction
– Velocity, acceleration, force, displacement

May be graphically represented
– Arrows

Despicable Me – Vector video clip
Vectors



Vectors are a method used to visually show forces
A vector is a quantity which has both magnitude (size)
and direction.
– The length of the arrow shows the magnitude of the
vector.
– The angle of the arrow shows the vector's direction.
Just like numbers, we can add two or more vectors
together and get a net force called the resultant
Adding 2 or More Vectors
Fig 1
Fig 2




Fig 3
Add vectors A and B to get the Resultant C
 A+B=C
Fig 1 - shows the magnitude & direction of the 2 vectors we
are adding
Fig 2 – we move the beginning of vector B to the end of
Vector A, making sure to keep the magnitude & direction
exactly the same
Fig 3 – Connect the beginning of Vector A to the end of
Vector B, this is your “Resultant” C.
Combining Displacements

You can add vectors using “vector
addition”

When two displacements have the same
direction, you can add their magnitudes.

If two displacements are in opposite
directions, the magnitudes subtract from
each other.
Displacement along a Straight
Line
Displacement that isn’t along a
straight path
Suppose a person moves 3 meters from A to B and 4 meters from B to
C as shown in the figure. The total distance traveled by him is 7
meters. But is he actually 7 meters from his initial position? No, he is
only 5 meters away from his initial position i.e., he is displaced only by
5 m, which is the shortest distance between his initial position and
final position.
Use Pythagorean’s Theorem!
a2 + b2 = c 2
Distance vs. Displacement
Problems

http://www.tutorvista.com/content/physic
s/physics-i/motion/distance-anddisplacement-animation.php
Distance vs. Displacement
David walks 3 km north, then turns and walks 4 km
east.
 Amy runs 2 miles south, then turns around and runs
3 miles north.
 Jermaine runs exactly 2 laps around a 400 meter
track.
 Derrick crawls 4 feet then turns 90 degrees and
crawls 6 feet.
 Ray runs 30 feet north, 30 feet west, and then 30
feet south.
 Jamison turns around 5 times.
 Cassidee walks 1 mile then turns 90 degrees and
walks 2 miles.
 Taja walks two miles from her door to the park, then
returns home to her door.

Distance vs. Displacement
continued







Sandy ran 3 blocks north, and then 2 blocks west.
Neva swam 3 complete laps in a 50 meter pool. ( 1 lap is to the
other side and back)
John flies at a heading of 90 degrees for 20 km, turns to 270
degrees and flies for another 10 km before crashing into a flock
of geese.
Cameron flies at a heading of 180 degrees for 13 km, turns to 90
degrees and flies for another 30 km before crashing into the
Alico building.
Marissa flies at a heading of 270 degrees for 5 km, turns to 90
degrees and flies for another 10 km before crashing into Alex
Alex flies at a heading of 0 degrees for 3 km, turns to 270
degrees and flies for another 4 km before crashing into Marissa
Taylor flies at a heading of 90 degrees for 20 km, turns to 180
degrees and flies for another 25 km before crashing into a Bob
Marley billboard.
Example problems

What is the total distance of a person who
over the course of a week ran a 5Km,
10Km, and biked a 150Km?

Julia drove 2.56x105 m S to school today,
and then drove 1.42x103 m N to
Samantha’s house after school. What was
her total displacement?
More Examples

Chris drove 1300m W to Logan’s house
then they drove 2500m S to meet Brittany
and Whitney at Whitney’s house. From
there they all drove 3800m E to watch the
JV Football game, what was Chris’ total
displacement?
Speed!!

Begins here!!
Distance-Time Graphs
The distance traveled by an object in a
period of time often is expressed using a
line graph. A line graph visually conveys
information using sets of data points.
200
1. Copy the blank graph below on your
paper. Complete the graph by plotting
the given data points on the graph.
Each set of data points represents
(time, distance). Note that time is
measured in seconds and distance is
measured in meters. Connect the
plotted points with a straight line.
Data points: (0, 0), (2, 40),
(4, 80), (6, 120), (8, 160),
(10, 200)
2. Describe the motion shown on the graph
the object is traveling at a
constant speed
and/or that the object
traveled 200 meters
in 10 seconds
Speed

Comparison of time and distance
– A scalar quantity (what does this mean?)
 [magnitude only]
– Distance units include: inches (in), feet (ft), miles (mi),meters
(m), kilometers (km), centimeters (cm), light year, etc.
– Time units include minutes (min), seconds (sec), hours (hr),
years (yr), etc.
– Speed can be any distance unit divided by any time unit!!
– Mi/hr, ft/sec, km/min

Distance traveled per unit time
 S=d/t
 T=d/s
 D=sxt

(speed = distance/time)
What is the speed of a car that traveled 75 km
in 1.5 hr?

Please get out your Distance/Displacement
worksheet and your Speed Problems
worksheet!
Speed

Measured in m/s

If you travel 2m in 1 sec, what is your speed?

If you travel 15m in 12 sec, what is your speed?

Car traveling at 80km/hr. What is this speed in m/s?

80 km
hr
x
1 hr
3600 sec
x
1000m
1 km
= 22.2 m/s
If the Algebra Stumps you!!
V=d/t
T=d/v
D=vxt
Divide here!
Multiply here!
Speed Worksheet – p.1
Velocity is speed with a direction

Speed AND direction
– A vector quantity [magnitude & direction]
Written like: 125 miles/hour east or
83
m/sec towards the house
 What is the velocity of a jet that traveled 1623
mi North in 83 min?

– V=D/T
– =1623 mi / 83 min
– =19.5 mi/min North

You can add velocities just like you did
displacements, with vector diagrams
Some Conversion formulas you
may need:
Write these in your notes!!!!!
1
mile = 1.609 km
 1 km = .62 miles
 1 mile = 5,280 feet
 1 mile = 1,760 yards

Average speed - computed for the entire
duration of a trip

Instantaneous speed - measured at a
particular instant, like when you check
your speedometer
ppe
Average Speed

Avg speed = total distance / total time
V
=
d
/
t

If a object moves at 104 km/hr for 12 hours,
what distance has it traveled?

If an object moves 640 km in 11 hours, what is
its speed?
If a car moves at an average speed of 60 mi/hr
for 24 hours, what distance has it traveled?
What is this distance in kilometers?
 (1 mile = 1.609 km)

Average Speed vs. Average Velocity

Avg speed = total distance / total time
V
=
D
/
t

Avg velocity = total displacement / total time
V
=
D
/
t
The slope of a line on a distancetime graph is speed
Average Speed
(Average Velocity)
What is the average speed after two minutes?
What is the average speed between 2 and 4 minutes?
What is the average speed for the entire trip?
Answers on next slide!! Let’s see how you did!!

Answers for Average Speed
or Average Velocity
Average speed = total distance / total time
What is the average speed after 2
minutes?
total distance is 75m, total time
is 2 minutes.
S = D/T
S = 75m / 2min
S= 37.5 m/min
What is the average speed between 2 & 4 minutes?
total distance: 110m – 75m = 35m
total time: 4min – 2min = 2minutes total time
S = D/T
S = 35m / 2min
S= 17.5 m/min
Speed
Constant Speed

Speed that does not change
– Instantaneous speed that does not change
Velocity Video Clip

C:\Movies\Physical
Science\Motion\phy03_vid_velocity\phy03
_vid_velocity_300.mov
This is on my hard drive at school…if you
are looking at this on my website, click the
link below and view the video
 http://www.teachersdomain.org/resource/
phy03.sci.phys.mfw.velocity/

Acceleration!!!

Begins here!!
Speed-Time Graphs
The speed an object travels in a period of 1. Describe the speed of the
time can be expressed on a graph. This
object shown on the graph.
type of graph can give useful information
2. The slope of the line on a
about the object’s motion. The speed-time
distance-time graph
graph of the object in Section 11.2 Interest
represents the change in
Grabber is shown below.
distance (m) per the change in
time (s). Thus, the slope of a
distance-time graph gives
speed (m/s). What information
does the slope of a speed-time
graph give you?
3. What is the slope of the line on
the speed-time graph?
1.
Describe the speed of the object shown on the graph.
The object is traveling at a constant speed of 20 m/s.
2.
The slope of the line on a distance-time graph
represents the change in distance (m) per the change in time (s).
Thus, the slope of a distance-time graph gives speed (m/s). What
information does the slope of a speed-time graph give you?
The slope of a speed-time graph represents the
acceleration of the object—its change in speed over
the time.
3.
What is the slope of the line on the speed-time graph?
The slope of the line is 0.
Acceleration
a change in speed, direction, or both.
 It is a vector
 We usually talk about positive
acceleration, like a car speeding up or a
rocket taking off.
 It can also be negative, like a car braking.

Acceleration

A change in velocity
– Speeding up
 Positive acceleration
– Slowing down
 Negative acceleration
 Deceleration
– Changing direction
Acceleration

The change in speed or velocity over time
– In the scientific community, the symbol for
“change” is the triangle:
– Change in velocity is found by subtracting the
initial speed from the final speed
Vf - Vi =
V
The formula for acceleration is:
A = Vf - Vi =
V
time
time
vf is final velocity
vi is initial velocity
Therefore the units for
acceleration are going
to be a
distance/time/time
Example
ft/min/sec

Notice if vi > vf you will have a negative
acceleration!
Acceleration

For an object to accelerate it
must:
– Speed up (positive acceleration)
– Slow down (negative acceleration a.k.a deceleration )
– Change direction of travel
3
1
2
Each of these pictures depicts a type of acceleration:
1: the shuttle is speeding up every sec of the flight into orbit
2. the horse has come to a screeching halt (slowing down)
3. the baseball thrown to the batter is hit into the outfield
(changed direction)
Change in direction
Any time an object turns it has an
acceleration
 Even though the speed may be constant,
the direction is changing
 Constant acceleration is a steady change
in velocity

Video Clip on Displacement,
Velocity, and Acceleration

http://www.youtube.com/watch?v=ITs6F1
_6qBM
Acceleration
due to gravity
Known as free fall
 As something falls its velocity
increases by 9.8 m/s every second
 Acceleration due to gravity =
9.8 m/s2


Falling objects video clip

Myth busters Falling objects
Rolling ball incline video clip that shows
how constant acceleration affects an
object's motion.
 Video clip
 If you are viewing this on my website, you
can use this link:
 http://www.teachersdomain.org/resource/
lsps07.sci.phys.maf.ballincline/

Review: Distance vs. Time graph

The slope of a line on a distance-time
graph is
– speed
Speed vs. Time graph
Graph speed on y, time on x
 Slope equals

– acceleration.

The slope of the line
represents
– The speed

How does the slope
during the first second
compare to the slope
during the fourth second?
– It is much greater during
the fourth than the first

What does this mean?
– An increasing speed means
that the ball is accelerating.
What does it mean?
What does a = 5 [m/sec2] mean?
 If an object starts at rest, its velocity
increases by 5 [m/sec] every second.

Time (sec)
0
Acceleration
5 m/sec2
Velocity
0 m/sec
1
2
3
5 m/sec2
5 m/sec2
5 m/sec2
5 m/sec
10 m/sec
15 m/sec
4
5 m/sec2
20 m/sec
Therefore, an object accelerating at 5m/sec2 will be travelling
at 20 m/sec after 4 seconds.
Acceleration Problems:

Calculate acceleration for the following data:
A = 60km/hr - 20 km/hr = 4 km/hr
10 sec
sec
A = 150m/sec - 50 m/sec = 20 m
5 sec
sec2
A = 1200km/hr - 25 km/hr = 587.5 km/hr
2 min
min
Interactive On-Line Quiz

Motion, Acceleration, Velocity
– (http://www.quia.com/quiz/286600.html?AP_r
and=777689445)
Motion Graphs

Here is a power point presentation on
Motion Graphs…this is also on my website.

You need to be able to interpret these!!
Check this out??!!
Virtual lab on velocity and acceleration in
case you don’t understand!!
 http://www.teachersdomain.org/resource/
phy03.sci.phys.mfw.accel/

Inquiry Activity

How Does a Ramp Affect a Rolling Marble?
Warm-up #44

What are the formulas to calculate:
– velocity
– acceleration
• What are the formulas to calculate:
– velocity
– acceleration