•
How long did it take for the sound to reach you?
•
How long did it take the bee to reach the elephant?
•
How fast was the bee flying?
•
If the bee returns promptly to his starting position
maintaining the same speed, what
was his average velocity?

Interpreting Velocity Graphically
•
The
instantaneous velocity
is the velocity of an
object at some instant or at a specific point in
the object’s path
The instantaneous velocity
at a given time can be
determined by measuring
the slope of the line that is
tangent to that point on
the position-versus-time
graph

Check Point
Do you calculate instantaneous velocity the
same way you calculate
average velocity?
What is the difference?

9/17
•
HW- Book p. 49 1-5.
Graphs must be done by
Monday!
•
Describe the motion of the objects in the
following graph

Acceleration

Objectives
•
Describe
motion in terms of changing velocity.
•
Compare
graphical representations of
accelerated and non-accelerated motions.
•
Apply
kinematic equations to
calculate
distance, time, or velocity under conditions of
constant acceleration.

•
Acceleration
is the rate at which velocity
changes over time.
average acceleration =
•
An object accelerates if its
speed,
direction, or
both
change.
•
Acceleration has direction and magnitude.
Thus, acceleration is a
vector
quantity
a
avg
=
=
SI
Unit: m/s
2

Data and Graphs from Yesterday
•
Now take the data and for each trial, convert each
data set into velocity (y axis) and time (t on x axis)
•
Make sure you clearly label the trials and the type of
motion that was occurring
•
Look at the lines that were produced on each graph
and describe the motion at each line segment (you
may neatly write this on the graph). Here you are
making mental comparisons between the first graphs
which show P-T and these graphs which show V-T
•
Calculate the slope and area under each line segment
for Each Trial (you may neatly write this on the graph)

Finding Displacement During Constant
Acceleration
•
Remember that velocity is displacement (∆ x) over
time so with some rearranging, we can get a new
equation from acceleration that allows us to find
out how far and object traveled given it’s velocities
and the time of the motion.
t
v
v
x
i
f
)
(
2
1

What if?
•
A plane starting at rest at one end of the
runway undergoes uniform acceleration of 4.8
m/s/s for 15 s before takeoff.
•
What is the speed at takeoff?
•
How long must the runway be for the plane to
takeoff?

Finding Velocity with Constant Acceleration
Finding Displacement with Constant
Acceleration
All
we are doing is
rearranging the first two
equations!
at
v
v
i
f
2
2
1
at
t
v
x
i

•
At the Dixie Stampede in Pigeon Forge, the pig
Abraham Linksausage ran around a circular
path. Suppose Abe can run at a max speed of 2
feet/sec. If he started from rest and underwent
constant acceleration with a magnitude of
0.5m/s/s, what distance did he have to run to
reach his max speed?

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