Motion from rest, aconstant

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Motion from rest, aconstant
Part of motion is past 1.5-m window
Let the physical point at which the object
achieves Vavg be called point P
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(No Transcript)
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Point P always happens at time t/2. Where it
occurs is a different matter. One limiting
case-- Object dropped from Top of window.
Sum of yellow and green L gt2/2
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What happens in between say the object is dropped
from 10 m above the window?
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PRS Question 2
A ball thrown straight up reaches a highest
point and then falls straight down. At the
highest point,
y
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Solution

• Going up the ball has positive velocity, while
• coming down it has negative velocity. At the top
• the velocity is momentarily zero.
• Since the velocity is
• continually changing there must
• be some acceleration.
• The answer is (3) v 0, but a ? 0.

y
t
v
t
a
t
Note switch from x(t) to y(t)
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Acceleration is due to gravity, constrained by
the presence of the inclined plane
Experiment shows that
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MOTION ON AN INCLINED PLANE
x
t
v
t
a
Labels and algebraic signs depend on your choice
of coordinate system!
t
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Move and invert coordinate system
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MOTION ON AN INCLINED
PLANE roles of coordinate system and initial
conditions are crucial