aim: how can we determine acceleration on a distance-time graph? do now: determine the displacement...
TRANSCRIPT
Aim: How can we determine acceleration on a distance-time
graph?
Do Now:
Determine the displacement of the following graph:
AB
C
D E-5
-4
-3
-2
-1
0
1
2
3
4
5
0 1 2 3 4 5 6 7 8 9 10 11
time (s)
velo
city
(m
/s)
d = bh = (5 s)(5 m/s) = 25 m
d = ½bh = ½(2 s)(5 m/s) = 5 m
d = ½bh = ½ (2 s)(-5 m/s) = -5 m
d = bh = (2 s)(-5 m/s) = -10 m
Total displacement = 15 m
Describe the motion on the following distance-time graph:
A
B
C
D Constant positive slope = constant velocity forward
Curved line = changing slope = acceleration
Positive slope = forward =accelerating foward
Constant positive slope = constant velocity forward
Is the object speeding up or slowing down?
•Determine if the slope is increasing or decreasing
A
B
C
D
Slop
e 1 Slope 2Slope 2 is less steep than slope 1
This means that slope 2 is moving with a slower velocity
In other words, the object is slowing down
Since the slope is still positive, the object is mowing forward
Slowing down forward
Slope 1
Slope 2
•Slope 2 is steeper than slope 1
•Both slopes are positive
Speeding up forward
Slope 1
Slope 2
•Slope 2 is steeper than slope 1
•Both slopes are negative
Speeding up backward
Slope 1
Slope 2
•Slope 2 is less steep than slope 1
•Both slopes are negative
Slowing down backward
Describe the motion on the following distance-time graph:
distance
time
A B
C
D
E F
G
H
I J
__
AB: At rest
__
BC: Speeding up forward
__
CD: Constant velocity forward
__
DE: Slowing down forward
__
EF: At rest
__
FG: Speeding up backward
__
GH: Constant velocity backward
__
HI: Slowing down backward
__
IJ: At rest
Instantaneous Velocity
This is velocity at a specific moment in time
On a distance-time graph:
Find the slope of the line on the graph using points one second before and one second after the time indicated
Find the instantaneous velocity at 14 seconds
0
20
40
60
80
100
120
140
160
13 14 15
time (s)
dis
tan
ce (
m)
If you just went 100m/14s, you would get an incorrect answer!
On a velocity-time graph
Just read the graph
0
5
10
0 1 2 3 4 5 6 7
time (s)
velo
city
(m/s
)
What is the instantaneous velocity at:
1 s
5 m/s
3 s
5 m/s
5 s
10 m/s