Lecture series accompanying Conceptual Physics, 8th ed'

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Lecture series accompanying Conceptual Physics,
8th ed.
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Aristotle on Motion (18)
Bummer, I was wrong!
2400 years agoGreek philosophertried to explain
motion
Natural motionwhat was observed.
Violent motionpushed or pulled.
The problem was that for the next 2000 years
nobody questioned Aristotles writing.
Copernicus and the Moving Earth (20)
He didnt publish his heliocentric theory until
near the end of his life because he was afraid
and unsure.
Aristotles view had become part of the
established order.
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Galileo
And the Leaning Tower (20)
Galileo, an early scientist, provided evidence
through observation and experiment.
Expt.- the story of dropping different masses
from the leaning tower to show that they all fell
in the same time.
Another expt. Galileos Inclined Planes
(21)
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Galileo imagined a world without friction.
An object rolling across the floor would keep
going because
INERTIA
because it possessed (wait for it)
Answer on p 22.
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Description of Motion (23)
Distance
Speed

time
Actually, this is the average speed.
The official formula is
d v t
As t approaches zero, the average speed becomes..
the instantaneous speed
Answers on p 24
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Velocity (25)
-A vector quantity because it has magnitude and
direction.
-Speed is a scalar quantity because it has only
magnitude.
Why?
Because its direction is changing.
Answer is on p25
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ACCELERATION (26)
It is the RATE of change of velocity with time.
The official formula is
? v
(vf vi)
a

? t
(tf ti)
Answers on p 26.
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Acceleration on Galileos Inclined Planes (27)
G. didnt have a stop watch so he used inclined
planes to slow things down.
This formula always matched his data regardless
of weight and size
v a t
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How Fast (28)
An object in
free fall
Accelerates at 9.8m/s per
sec.
Vat?
The rate of change of velocity is 9.8 m/s every
second.
g 9.8 m/s2
Answer p 28
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How far (29)
Heres the formula
d vot ½ a t 2
Usually vo 0
How far does a rock fall in 3 seconds if you
throw it downward at an initial speed of 4.0m/s?
d
(4.0m/s)
(3.0s)

½
(9.8m/s2)
(3.0s)2
56m
IN FREE FALL
The end.