Physics 2211: Lecture 14

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Physics 2211 Lecture 14
Galilean Relativity
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Galilean Transformation between frames
Newtons laws are valid in S and S
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Galileos transformation works well when the
relative velocity V is small compared to speed of
light.
If not, there is a correction due to Einstein
We will stick with Galileo
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B
A
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Relative Motion...

• What is the velocity of the plane in an IRF
  attached to the ground?
• Vp,g is the velocity of the plane w.r.t. the
  ground.

(directly across)
Vp,g
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Relative Motion...
Tractor

• Vp,g Vp,a Va,g Is a vector equation
  relating the airplanes velocity in
  different reference frames.

Va,g
Vp,a
Vp,g
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point boat upstream
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You are swimming across a 50 m wide river in
which the current moves at 1 m/s with respect to
the shore. Your swimming speed is 2 m/s
with respect to the water. You swim across in
such a way that your path is a straight line
perpendicular to the river bank. How many seconds
does it take you to get across?
1 m/s
50 m
(1) 50 (2) 35 (3) 29 (4) 25
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Choose x axis along riverbank and y axis across
river
The time taken to swim straight across is t L
/ vy
Since you swim straight across, you must swim
upstream so the x component of your velocity with
respect to the water exactly cancels the velocity
of the water in the x direction
1 m/s
2 m/s
m/s vy
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A glass elevator in a building atrium moves down
at constant speed V. A person in the elevator
drops a ball a height H above the elevator floor.
How far does the ball drop before it hits the
elevator floor from the point of view of a person
in the atrium?
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Recap
More Projectile Motion Galilean Relativity
Next Lecture
Kinematics of Circular Motion