Navigate [[..:..:activities:link|back to the activity]]. ===== 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?