Physics 106P: Lecture 1 Notes

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2
Suppose I drop a basketball off the roof and it
bounces off the ground below. Which of the
following graphs best describes its height above
the ground as a function of time
B)
A)
y
y
C)
D)
t
t
3
You throw a ball straight up into the air and
catch it as it falls back down. Just after you
throw it, the velocity of the ball A) is
zero B) is positive C) is negative
(A positive velocity means that the ball is
moving upward)
4
You throw a ball straight up into the air and
catch it as it falls back down. Just before you
catch it, the velocity of the ball A) is
zero B) is positive C) is negative
(A positive velocity means that the ball is
moving upward)
5
You throw a ball straight up into the air and
catch it as it falls back down. At the top of
its path, the velocity of the ball, A) is
zero B) is positive C) is negative
(A positive velocity means that the ball is
moving upward)
6
You throw a ball straight up into the air and
catch it as it falls back down. Just after you
throw it, the acceleration of the ball A) is
zero B) is positive C) is negative
(A positive acceleration means that the velocity
of the ball is changing in the positive
direction)
7
You throw a ball straight up into the air and
catch it as it falls back down. Just before you
catch it, the acceleration of the ball A) is
zero B) is positive C) is negative
(A positive acceleration means that the velocity
of the ball is changing in the positive
direction)
8
You throw a ball straight up into the air and
catch it as it falls back down. At the top of
its path, the acceleration of the ball, A) is
zero B) is positive C) is negative
(A positive acceleration means that the velocity
of the ball is changing in the positive
direction)
9
Newton's Third Law tells us that forces always
come in pairs. The other way to state this is
that every force has an equal and opposite
reaction force associated with it. If this really
true, how come these equal and opposite forces
don't just cancel each other out and nothing ever
moves? A) If force A is the action force, there
is a force B that occurs in response to A. They
are not simultaneously occurring. B) It's true,
because everything has a different mass, so the
effect of the forces are not the same on
everything. C) On a cosmic scale, this might be
what is actually happening. As for our little
world, there are currently too many already
active forces being exercised on us for there to
be motionlessness. D) Because only one of the
two forces in the pair of forces acts on any
given object, so for that object the pair of
forces dont cancel. E) Because there is a
initial, stronger force that starts an object
moving, but then the forces become equal.
10
How do airplanes fly ?
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Wing forces air down Newtons 3rd law says there
must bean upward force on the wing !
12
Bernoullis Principle Wherever air velocity is
high the pressure is lower.
demos
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