Date: Wed, 12 May 1999 23:00:19 -0700
From: Dan <dgray@justin-siena.napanet.net>
To: Pinhole Listserv <pinhole@exploratorium.edu>
Subject: Re: pinhole Re: Behavior of coins on free-fall rides
How about this: while the vehicle is at rest, all of the weight is on the point
of support, whatever that may be. Now, no matter how quick the release process
is, it can't be instantaneous and affect the whole vehicle at the same time.
So I can see the release process exerting slightly different forces on
different parts of the vehicle as it is being released. This could produce
oscillations in the vehicle that could result in the coin getting a slight
relative push upward producing the effect you noticed. What do you think?
Dan Gray
Justin-Siena HS
Richard White wrote:
> 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
>
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