describing motion kinematics §2.1–2.2. the tortoise and the hare told in words, formulas, and...
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![Page 1: Describing Motion kinematics §2.1–2.2. The Tortoise and the Hare Told in words, formulas, and graphs](https://reader035.vdocuments.net/reader035/viewer/2022062407/56649d215503460f949f67f0/html5/thumbnails/1.jpg)
Describing Motion
kinematics
§2.1–2.2
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The Tortoise and the Hare
Told in words, formulas, and graphs
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Group Work
Describe the Tortoise-and-hare race using a position-time graph.
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CPS Question
Who was fastest?
A. The tortoise.
B. The hare.
C. They had the same speed.
D. What do you mean by faster?
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Speed
average speed = xt
over entire interval
Rate of changing position
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CPS Question
Who had the fastest average speed?
A. The tortoise.
B. The hare.
C. Their average speeds were the same.
D. Over what time interval?
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Speed Units
distance
time= m/s
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Example Problem
You are working for the summer on the Wyoming Search and Rescue Squad when you get a call of a downed aircraft. The plane took off from Cheyenne at 12:15, flew north 100 miles and then 80 miles in a direction 30° north of west, where it vanished from radar at 1:05.
What was the average speed of the plane?
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Speed as Slope
Speed = distance
time
distance
time
= slope of graph!
d
t
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Instantaneous speed
finite t
Young and Freedman, Figure 2.7
smaller t limt0
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Speed
xt
at one instantinstantaneous speed = limt 0
= dx/dt
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CPS Question
Who had the fastest maximum instantaneous speed?
A. The tortoise.
B. The hare.
C. Their instantaneous speeds were the same.
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Illustrating Motion
Young and Freedman, Fig. 2.8
x-t plot motion diagram
Can we make a motion diagram of this race?
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Group Work
Describe the Tortoise-and-hare race using a velocity-time graph.
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Constant-Velocity Motion
• v = x/t = constant throughout process
• x = vt• xf = xi + x = xi + vt
• Can also use this with average v
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Speeds and Areassp
eed
timet1 t2 t3
hare
tortoise
area = vt = distance)
t0 t4