Fixed and Rotating Reference Frames

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Fixed and RotatingReference Frames

• Created for CVCA Physics
• By
• Dick Heckathorn
• 2 December 2K 4

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B
A
C
D
A
C
D
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A smooth, level table, is centered on a platform
which rotates uniformly at a rate of one
revolution in 12 seconds.
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B
A
C
D
Two perpendicular lines are drawn through the
center of the table, intersecting a circle of
1.20-meters radius at the points A, C, B, and
D.
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I
H
A
C
Two people, a girl at H and a boy at I sit on
the platform at opposite ends of the lines AC.
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J
I
H
A third person, J, is above the table so that she
can observe the motion of a dry Ice puck in a
stationary frame of reference.
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A
C
D
She sees four marks on the floor, forming two
perpendicular reference lines AC and BD through
the center of the table. (B is behind the table.)
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H
A
C
a. As the platform is rotating, the girl holds
the puck in her hand. What is its velocity in Js
frame of reference at the instant A crosses the
line AC?
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D ? B (into screen)
In direction ?
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A
C
b. As the girl passes A she gives the puck a
sudden push so that it travels along line AC with
a speed of 0.40 m/s. Construct a vector diagram
to show the velocity that the girl gave the puck
in Js reference frame.
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• Given
• Initial velocity of puck Vi
• Final velocity of puck Vf
• Unknown
• Velocity of pushed puck Vp
• Relationship
• Vi Vp Vf
• Vp Vf - Vi

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B
vi
0.63 m/s
vf
0.40 m/s
C
A
57o
0.74 m/s
-0.63 m/s
-vp
-vi
D
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c. Construct a diagram which shows the position
of the puck and of A at 1, 2, 3, 4, 5, and 6
seconds in Js reference frame.
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d. Make use of the diagram constructed for (c) to
construct a diagram which will show the motion of
the puck on the table, as seen by H and I.
These points can be connected to give a picture
of the motion in the moving frame.
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Thats All Folks