Speed, Velocity, and
Acceleration
Speed
• The amount of distance traveled per unit
of time.
Speed= Distance
Time
FRICTION
Friction is a contact force that opposes motion, it
causes heat, damage, wear and slowing
Friction can be reduced by…
lubrication,
streamlining (aerodynamics),
slowing down,
smoothing surfaces
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Speed, Distance, Time
Formulas
Formula Triangle
How to Use the Formula Triangle
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Calculating Speed
Given Distance & Time
Divide Distance by Time
Distance ÷ Time = Speed
Speed = Distance ÷ Time
Practice:
Angie ran 15 meters in 5 seconds. What
was her speed?
D
S
Speed = Distance
T
Speed= 15 m
Time
5s
Speed = 3 m/s
Calculating Distance
Given Speed & Time
Multiply Speed and Time
Distance = Speed X Time
Speed X Time = Distance
3
Practice:
• If a car is traveling at 20 m/s, how far will it
travel in 60 seconds?
D
S
Distance = Speed X Time
Distance = 20 m/s X 60 s
T
Distance = 1,200 m
Calculating Time
Given Distance and Speed
Divide Distance by Time
Distance ÷ Speed = Time
Time = Distance ÷ Speed
Practice:
• A train traveled at a speed of 50 m/s. How
long did it take the train to travel 3,000 m?
D
S
Time = Distance
T
Time = 3,000 m
Speed
50 m/s
Time = 60 s
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Motion Graphs
Interpret The Graph Below:
Interpret The Graph Below:
The graph shows
an object which
is not moving (at
rest).
The distance
stays the same
as time goes by
because it is not
moving.
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Interpret The Graph Below:
Interpret The Graph Below:
The graph shows
that the objects
distance increases
as time passes.
The object is moving
and so it has
velocity.
The straight line
shows it is a
constant (not
changing).
Interpret The Graph Below:
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Interpret The Graph Below:
Just like the
previous
graph, this
graph shows
an object
moving with
constant
velocity
Interpret The Graph Below:
Interpret The Graph Below:
The curve in the
graph shows
that the objects
velocity is
changing as time
passes.
This is
acceleration.
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Interpret The Graph Below:
Interpret The Graph Below:
In the first part of
the graph the object
is moving with
constant velocity.
In the second part of
the graph the object
is at rest (not
moving).
In the third part the
object is again
moving with
constant velocity.
SPEED QUESTIONS
What would these look like on a distance/time graph?
1. stopped
2. slow
3. fast
4. accelerating
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DISTANCE/TIME GRAPHS
A car takes 1.5 minutes to travel 500m down a busy road. It stops
at lights for 30 seconds, then continues on for 1 minute as it goes
another 1km.
Plot this on a distance/time graph.
Using the distance/time
graph:
1.5
Distance
1
∆d =
1km
Steepest
section is
fastest
(km)
1.What is the total distance
0.5
traveled?
= 1.5 km
2. In what part of the trip is
the car going the fastest? = part 3
3. What is the fastest
speed?
v = ∆d / ∆t
v = 1km/1min
∆t =
1min
1
2
Time (min)
3
In a distance/time graph
the slope of the line =
the speed of the object.
Velocity
• Velocity is like speed, but it includes a
change in position.
• Velocity is stated as speed and direction
Example:
The car was traveling at 60 miles per hour to
the east.
Velocity (continued)
• Stand up and take 2 steps backwards.
• Now take 2 steps forward.
Did you walk at a certain speed?
Yes. You took a total of 4 steps over the
span of a few seconds.
Did you have velocity?
No, because your position didn’t change.
You ended at the same point you started at.
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Acceleration
• Acceleration is the rate at which an
object’s velocity changes.
This includes
– Changing speed
– Changing direction
Interpret The Graph Below:
Interpret The Graph Below:
The graph shows
that the objects
velocity does not
change as time
passes.
It shows constant
velocity.
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Interpret The Graph Below:
Interpret The Graph Below:
The graph shows
that the objects
velocity is
increasing as time
passes – it is
accelerating.
The straight line
shows that it is
constant
acceleration.
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