Unit 2.2 Acceleration
Teacher: Dr. Van Der Sluys
Objectives
• One dimensional Motion
– Acceleration
Which car or cars (red, green, and/or
blue) are undergoing an acceleration?
Back
1
Acceleration
• Acceleration (a) is a vector that describes the
change in velocity as a function of time.
a
=
Δv
Δt
vf - vi
tf - t i
=
• It is possible to have both positive and
negative acceleration.
Graphical Representation of
Acceleration
• An object is accelerating when the velocity
versus time plot has a nonzero slope.
C
Accel
Velocity
A
B
D
Position versus Time and
Velocity versus Time Graphs
Which graph corresponds to the red, green and blue cars?
Velocity
What would the velocity versus time graph look like?
Which graph(s) represent acceleration?
2
Displacement, Velocity and
Acceleration Graphs
Comparing Displacement,
Velocity and Acceleration Graphs
What is Deceleration?
“When an object is slowing down, we sometimes say
it is decelerating. But be careful: deceleration does
not mean that the acceleration is necessarily negative.
For an object moving to the right along the positive x
axis and slowing down (as in Fig. 2-10), the
acceleration is negative. But the same car moving to
the left (decreasing x) and slowing down has a positive
acceleration that points to the right, as shown in Fig. 211. We have a deceleration whenever the velocity and
acceleration point in opposite directions.”
“Physics”, Giancoli, 5th ed., Prentice Hall, pg. 26
3
Examples of Deceleration
“Physics”, Giancoli, 5th ed., Prentice Hall, pg. 26
Draw the Missing Graphs
Accel.
Velocity
Position
T
Can you walk the walk?
Draw the Missing Graphs
Accel.
Velocity
Position
T
Can you walk the walk?
4
Draw the Missing Graphs
Accel.
Velocity
Position
T
Can you walk the walk?
Draw the Missing Graphs
Accel.
Velocity
Position
T
Can you walk the walk?
Draw the Missing Graphs
Accel.
Velocity
Position
T
Can you walk the walk?
5
Draw the Missing Graphs
Accel.
Velocity
Position
T
Can you walk the walk?
Draw the Missing Graphs
Accel.
Velocity
Position
T
Can you walk the walk?
6