1. Fixed and Rotating Reference Frames
Created for CVCA Physics By
Dick Heckathorn
2 December 2K + 4

2. B’ C’ A’ D’ A C D

3. A smooth, level table, is centered on a platform which rotates uniformly at a rate of one revolution in 12 seconds.

4. B’ C’ A’ 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’.

5. I’ H’ C’ A’
Two people, a girl at H’ and a boy at I’ sit on the platform at opposite ends of the lines A’C’.

6. 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.

7. C A 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.)

8. H’ C A
a. As the platform is rotating, the girl holds the puck in her hand. What is its velocity in J’s frame of reference at the instant A’ crosses the line AC?

9. In direction ?
D  B (into screen)

10. C A
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 J’s reference frame.

11. Given:
Initial velocity of puck Vi
Final velocity of puck Vf
Unknown:
Velocity of pushed puck Vp
Relationship:
Vi + Vp = Vf
Vp = Vf - Vi

12. 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

13. c. Construct a diagram which shows the position of the puck and of A’ at 1, 2, 3, 4, 5, and 6 seconds in J’s reference frame.

15. 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.

17. That’s All Folks