Re: Interesting observation.

[Nils Sorensen <nsorens@FAS.HARVARD.EDU>]

> Hi,
>
>        On The U of Az campus today is a small merchant fair
> including shows by rollerbladers in a big (10-12 meters
> across) U shaped surface.  At the peak of the U, the skaters
> could either turn around and go back down or land on a
> platform.  How can that be, since at its top the U appears
> to be going straight up.  A marble in a similar track would
> head right back down and could not land on the platform.
>
>        Could it be the motion of the skaters Center of
> Momentum is not the same as the skates?
>
>
> Thanks
> Roger


Hi,

        I have seen similar shows with skateboards, rollarblades, and
bicycles.  The athlete has control over their height above the top of the
half-pipe with control over their speed and also how they push off from the
top. In this case they choose simply not to push off, and also have a
slower approach speed. Now they can "step-out" of the pipe onto the
platform.
        I have found that some of the newer sports help in teaching
physics. Use some "extreme (ly stupid and dangerous) sport" to help show
rotational motion. A video tape of snow boarding, VCR with a good pause
button, and a dry erase marker to mark axis of rotations can make for a
nice lesson on rotational motion.


                                                        Nils