Date: Wed, 12 May 1999 22:38:09 -0700
From: Richard White <rwhite@telis.org>
To: Pinhole Listserv <pinhole@exploratorium.edu>
Subject: Re: Behavior of coins on free-fall rides
Hello!
I am confused about observations made over the years on a number of
different amusement park free-fall rides. Any hypotheses -- or better
yet, knowledge -- would be appreciated!
The behavior of coins and various other objects on these rides has been
observed by many, and even documented on the Great America videotape:
an object at rest at the top of the ride doesn't appear to accelerate
quite as quickly as the car and rider do when the car is released from
the top of the tower. As the car and rider fall, the object floats up
until it is at least several centimeters above the surface it was
resting on. It falls back down to its original resting surface once the
car begins decelerating at the bottom, of course. I've heard a number
of bad explanations and some plausible ones that later turned out to be
wrong, but noone seems to have nailed it yet. (The Great America
videotape mysteriously states that their demonstration water balloon,
held in some kind of paper tub, floats up due to an "inertial reflex".
What is that??!)
In my most recent experiment, conducted at Great America last week, I
placed a nickel inside an empty plastic peanut butter jar, screwed the
lid on tight, and held the jar against the restraint bar that locked me
into place. The jar was held against the bar in order to eliminate the
effects of any bodily movement on my part, and the lid was screwed on
tight in order to eliminate the possible effects of air pressure
(Bernoulli's Principle had been suggested as a possible source of lift
on the coin). I rode the car up. The car dropped. I watched the
nickel carefully. I watched it float about 5 centimeters above the
bottom of the jar for most of the ride down.
What's going on here? The two remaining of our initial multiple working
hypotheses are:
1) The car is given a slight acceleration downward at the beginnning of
the ride, slightly greater than 9.8 m/s^2.
2) The car is given a slight push UP (in order to release some catch
mechanism?) at the beginning of the ride, then dropped.
Does anyone have any info on this question?
Many thanks to my fellow physics teachers at Berkeley High who have
entertained my endless speculation on this topic, and thanks in advance
for a clear, lucid, and correct explanation!!!
Richard White
Physics, AP Physics
Berkeley High School