At 08:41 PM 1/25/03 -0600, Dan Minette wrote:
----- Original Message ----- From: "Ronn! Blankenship" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, January 25, 2003 2:48 PM Subject: Re: G-Whiz: Roller Coasters Get Astronaut Rating> At 11:51 AM 1/25/03 -0600, Dan Minette wrote: > > >----- Original Message ----- > >From: "Robert Seeberger" <[EMAIL PROTECTED]> > >To: <[EMAIL PROTECTED]> > >Sent: Saturday, January 25, 2003 11:23 AM > >Subject: G-Whiz: Roller Coasters Get Astronaut Rating > > > > > > > > "What we do know, and what has been substantiated by science" Gibson > >added, > > > "is that riding a roller coaster imposes less g-forces on the body than > > > flopping down in a chair, sneezing or skipping rope. Ridding a roller > > > coaster is far safer than many of our other ordinary daily activities." > > > >An interesting related trivia question. Say you drop something solid and > >moderately hard, like a solid piece of glass or a crystal, on a hard > >surface, like a tile floor. What are the g forces involved when the > >glass/crystal hits the floor? > > > > Depends on how quickly the falling object comes to a halt. > > Assuming it was dropped from a height h and started at rest, at impact it > will be moving downward with a velocity of sqrt(2gh), so the acceleration > it experiences will be a = sqrt(2gh)/<delta-t>, where <delta-t> represents > the time it takes the object to come to a halt. That would depend on > things like the elasticity and tensile strength of the object and the > floor, but I don't know of any equation to compute <delta-t>. Probably the > best method would be to use high-speed photography to measure the time the > impact takes . . . Or, to measure the shock when it happens. The MWD industry is the roughest enviornment that crystals (such as NaI crystals) and photomultiplier tubes are expected to perform in. OK, its a pretty standard test in the MWD industry. The g force for something dropped from a meter onto a hard surface is typically around 1000 g's. The shock pulse is about 0.005 s wide. There are specifications I've written for detectors (comprising of a photomultiplier tube and a NaI crystal) to survive these shocks, as well as 6 hours of 20 g rms random vibration.
Must be more stringent than the specs for the NaI(Tl) crystals and PM tubes I recall from the unclear lab, or PM tubes used in astronomy. Although fortunately I haven't actually tested any of them for impact resistance . . .
--Ronn! :)
I always knew that I would see the first man on the Moon.
I never dreamed that I would see the last.
--Dr. Jerry Pournelle
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