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[Phys-L] Re: water-rocket lifting a man?



I saw this too and wonder why the flight looked so different in
height and range from the different camera angles. I also wondered
why he did not spin in place like an model rocket engine launched
without a rocket (experience and regrets).
I had not thought about there being a tow line above and wondered if
the guy was riding a tether or rod for a bit so I looked at little
closer for some evidence. Capturing to quicktime and looking frame by
frame:

-in the scene where a man throws a inflated ring, before he throws
there is a cable that appears to be coming up from the dock behind
his head at angle consistent with the launch. Maybe.
- about three to four frames after launch, the bottle array is turned
nearly at right angle to the direction of motion yet he continues to
ascend. Some external force must be providing guidance.
- air time from the 'looking at the mountain' view is 119 frames. It
is also about the same time (+/-3 frames) from the 'looking to the
shore' view. I now think there was only one take and the video was
not doctored or spliced.
- about 40 frames of thrust. During that time he cork screws upwards,
but in an almost perfectly straight line as if he was twirling around
something.

How would the cable release mech. have worked? Could he be trailing a
second line that pulled release and set him free? I cannot see evid.
of the cable in the low res. copy I have.

Thanks Dwight, for hosting the clip. I had wanted to discuss this
clip with the forum too, but the last clip I referenced drew neg.
comments due to the dubiousness of the hosting site's sponsors. I
have a quicktime version of the clip I would be happy to email anyone
who wants it. Email me off list please (2.5Mb, low res).

Scott


*******************************************
Scott Goelzer
Physics Teacher
Coe-Brown Northwood Academy
Northwood NH 03261
s.goelzer@comcast.net
*******************************************


On Sep 23, 2005, at 3:31 PM, Dwight K. Souder wrote:

Some of my students are building a water-rocket launcher. Today,
while in
the library to try to collect more information, one of my students
stumbled
across this one website. They were laughing hysterically and
showed it to
me. It looks as though a bunch of water rockets were attached to
someone
and released...tossing the person into a lake. I'm sure these
things have
quite a bit of thrust to them, but part of the video doesn't look
quite
right. It almost looks as though the man is being lifted by some
other
means, perhaps by helicopter, and released. What are your thoughts?

Here is the website: http://polyplex.org/cjh/rockets/other/bpj.wmv

Enjoy,
Dwight
Ashland, OH

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