What is Motion?
Motion: A change in position of an object compared
to a reference point
Motion involves all of the following:
You fill in the blank!
Definition of Motion
Event that involves a change in the position or
location of something.
Motion is Relative
• Relative – it is described or compared to a
REFERENCE POINT
http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_pg7_relmotion/mfm05_p
g7_relmotion.html
• http://www.amnh.org/education/resources/card_fram
e.php?rid=937&rurlid=894
• Example: Are you moving at this moment? If
yes, then how are you moving?
• How does your movement look to another
person? (Can they tell you are moving?)
Displacement vs Distance
• Displacement - the
distance and direction of an
object’s change in position
from its starting point
• Distance – how far
something moves
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Displacement vs Distance
• Displacement - the
distance and direction of an
object’s change in position
from its starting point
• Distance – how far
something moves
•
http://www.absorblearning.com/media/item.action?quick=4n#
What is the Displacement?
• Problem - A physics teacher
walks 4 meters east, 2 meters
south, 4 meters west, and 2
meters north.
• What is the total
displacement of the
teacher?
• What is the total distanced
walked by the teacher?
And the answer is...
• Displacement = 0 m - The
teacher has returned to the
starting point.
• Distance = 12 meters
• The distance is 12 meters but the displacement is
zero. The teacher has “covered 12 meters on the
ground”, yet when he is finished walking, he is
not walking out of place.
Types of Motion
• Uniform motion - constant speed in a straight
line
• Accelerated motion – motion that is changing
in speed or direction
• Circular motion - speed is constant but the
direction of motion is changing continuously
What is Motion?
Speed
The rate of change in position
Speed = distance ÷ time or
Speed = distance
time
Speed
Types of Speed
• Average Speed
• Instantaneous Speed
• Constant Speed
Speed
Average Speed
• Comparison of time and distance
– Distance traveled per unit time
– Distance is referring to "how much ground an
object has covered" during the time it was in
motion.
• S=d/t
• T=d/s
• D=sxt
Speed
Instantaneous Speed
• Speed at any instant
Speed
Constant Speed
• Speed that does not change
– Instantaneous speed that does not change
– Example: After setting cruise control on a car,
your speed at any point will be the same until you
turn off the cruise control.
What is Motion?
Velocity
Speed plus direction
Example: 50 km/hour north
Velocity
• Speed AND direction -- Velocity must include
a speed and a direction.
Displacement is "how far out of place an
object is because of its motion”. Displacement
is the object's change in position.
What is Motion?
Acceleration
The rate of change in velocity
Positive acceleration = speeding up
Negative acceleration = slowing down (decelerate)
Acceleration = Vfinal – Vinitial
Time
Acceleration = ∆Velocity
Time
or
Acceleration "the rate at which an object changes its
velocity." An object is accelerating if it is changing its
velocity.
Acceleration
• A change in velocity
– Speeding up
• Positive acceleration
– Slowing down
• Negative acceleration
• Deceleration
– Changing direction
The Direction of Acceleration
Acceleration will always have a direction
associated with it. The direction of
acceleration depends on two things:
•
•
whether the object is speeding up or slowing
down
whether the object is moving in the + or direction
Circular Motion:
Continuous Acceleration
An object traveling in a circular motion is always changing its
direction. Therefore, its velocity is always changing, so it is
accelerating. This is known as centripetal acceleration.
200m/40s = 5 m/s
2 km/1000s = 0.002 km/s
or 2 m/s
100 m/10 m/s = 10s
50 m/s x 20s = 1000 m
20,000 m/ 40 m/s = 500 s
10m/20s = 0.5 m/s
40 m
40m/40s = 1m/s
25m/10s = 2.5 m/s
Steepest line
10m/s 2/ 5 s = 2 m/s
10m/s2 x 12s = 120 m/s
10m/s / 2m/s = 5 s
4000m/s /2s = 2000m/s2
40m/s x 10s = 4 m/s2
20m/s x 10s = 2 m/s2
60m/s x 20s = 3 m/s2
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Motion Graphs
Time – Distance Graphs
Motion Graph # 1
Straight, Flat Line
• As time passes, there is
no change in distance;
no motion
Motion Graph # 2
Straight, Increasing Line
• As time passes, distance
increases
• The change in distance is
constant – no stopping &
starting
Motion Graph # 3
Straight, Decreasing Line
• As time passes, distance
decreases
• The change in distance is
constant
Motion Graph # 4
Changing Line
• A changing line means
changing distance
• Distance increases 
then doesn’t change 
then decreases
Representing Motion in Graphs
Distance – Time
Velocity - Time
Describing a Distance - Time Graph
Describing a Velocity - Time Graph
Speed, Distance, Time Formulas
Calculating Speed
Given Distance & Time
Divide Distance
by Timeby Time
Divide Distance
DistanceDistance
÷ Time ÷
= Time
Speed= Speed
Speed =Speed
Distance
÷ Time ÷ Time
= Distance
Calculating Distance
Given Speed & Time
Multiply Speed and Time
Distance = Speed X Time
Speed X Time = Distance
Calculating Time
Given Distance and Speed
Divide Distance by Speed
Distance ÷ Speed = Time
Time = Distance ÷ Speed