🚀 go-pugleaf

Here's a belated reply to the request for gravity experiments.  This is
one I learned about from a high school teacher several years ago, which
I have used as a demonstration.
  One can measure g by rolling a marble around the inside edge of a
glass pie dish.  This is the standard problem about the banking angle
of a turn, except that we use it to find g.  If A is the angle the
side of the dish makes with the horizontal and v is the speed of the
marble as it rolls around, then we find

       g = v^2/(R tanA)

where R is the radius of the pie dish.  This is only approximate, of course,
but it works pretty well.  One "swishes"  the pie dish around slightly to
keep the marble rolling at a fairly constant radius about halfway up the
side of the dish.  Use a stopwatch to time about 10 revolutions of the
marble around the dish to find the speed.

Steve Luzader
Frostburg State University
Frostburg, MD
sluzader@fre.fsu.umd.edu