chapter 2 motion in one dimension. s, v, a displacement: ( m ) where you are velocity: ( m/s ) the...
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Chapter 2Motion in one dimension
s, v, a
Displacement: (m)Where you are
Velocity: (m/s)The rate of change of displacement
Acceleration: (m/s2)The rate of change of velocity
Note: Your textbook use x instead of s
Equations
Quick Examples
Useful facts about slopey
x0
The Signs of Slope (m)
m >0 m <0m =0
Slope = ± Rise over Run
Alternatively
You need two points to find a slope!
Find the slopes
Important: Unit of Slope!!!
Do not ignore the units! Different graph has different units.
Unit of slope = (unit of y-axis) / (unit of x-axis)
Unit of Slope!!!Unit of slope = (unit of y-axis) / (unit of x-axis)
Three graphs
slope slope
area area
Summary
Find the velocity at t = 1s, 2s
Hint: Find the slope
At t = 1s
At t = 2s
The sign of slope
Find the acceleration at t = 1s, 3s, 5.7s, 6.5s, 8s, 10s
Hint: Find the slopes at these times.
Vel
ocity
(m
/s)
Find a at t = 1s, 3s, 5.7s, 6.5s, 8s, 10sV
eloc
ity (
m/s
)
Instantaneous velocity versus average velocity
All the velocity we dealt with so far are “instantaneous velocity”, not “average velocity”.
Unless stated explicitly, velocity in general means “instantaneous velocity”.
Which is which?Questions about velocity are asked in either one of the two ways:
Average v or Instantaneous v?
Displacement and Area
Find the area
How far has the object traveled from 0s to 4s?
Watch out for negative area!V
elo
city
(m
/s)
Time (s)0
1m/s
-1m/s
2s 4s
If a line goes under the x-axis, the area it encloses is treated as negative.
+
-
Change of velocity is the area under the acceleration-
time curve
+-
If you don’t already know this…
Find the displacement between the following times:
Hint: Find the area.
Vel
ocity
(m
/s)
1) 0s to 5s2) 5s to 6s3) 6s to 10s4) 8s to 11s5) 2s to 8s
Find the displacement between the following times:
Vel
ocity
(m
/s)
1) 0s to 5s
Find the displacement between the following times:
Vel
ocity
(m
/s)
5s to 6s
Find the displacement between the following times:
Vel
ocity
(m
/s)
6s to 10s
Find the displacement between the following times:
Vel
ocity
(m
/s)
8s to 11s
Find the displacement between the following times:
Vel
ocity
(m
/s)
2s to 8s
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