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===== Merry-Go-Round: Instructor's Guide =====

==== Main Ideas ====

==== Students' Task ====
//Estimated Time: 10 minutes in class + 30--60 minutes outside class//

Start the chair/platform going counterclockwise, sit in it, and attempt the
following:

  * Roll a ball to a person standing beside the chair/table.
  * Roll a ball between your left and right hands in the radial direction.
  * Roll a ball between your left and right hands in the direction perpendicular to the radial direction.

Alternative task, requiring only a rotating whiteboard:

  * Mark a whiteboard with a rectangular coordinate grid, put it on a rotating platform, and, standing next to it, attempt to draw a straight line.

Predict/describe/sketch what happens in each case, both as seen by observers
on the ground and by observers on the rotating platform.

** WARNING: Students prone to dizziness should not be required to actually
   perform these tasks, but should instead observe other students. **

==== Prerequisite Knowledge ====

none

==== Props/Equipment ====

**This activity requires a merry-go-round!**

A suitable alternative can be constructed; what is needed is a rotating chair
with a flat desktop attached.\\\\
Another option is any mechanism which allows a whiteboard to spin smoothly.
\\\\
If all else fails, show the
[[http://www.youtube.com/watch?v=_36MiCUS1ro&NR=1|video]].

==== Activity ====

This activity should really be done outside of class, e.g. as homework, but it
is well worth spending some class time on it to get students started --- that
is, //if// you have access to an in-house merry-go-round or equivalent.

==== Wrap-Up ====

  * Which way does the ball (appear to) curve?
  * Show the [[http://www.youtube.com/watch?v=_36MiCUS1ro&NR=1|video]].  (Note that this merry-go-round goes //clockwise//.)

==== Extensions ====

  * Is a boomerang possible?
  * Are there trajectories with multiple loops?
  * Are there trajectories which loop forever?
  * What happens on a curved rotating surface, such as the Earth?