Ah! A materials person! And an experimentalist to boot! I suppose you'l be telling us shortly that the distribution of breaking strengths are not Normal, too.
Well, tensile strengths aren't, in the main, although one can often get a long way by ignoring this bit of subtlety. And yes, we should make every effort to (a) use realistic numbers in the problems, and (b) attach units on them always. Credibility with students often rides on them. Cheers, Jay (another materials person) "Robert J. MacG. Dawson" wrote: > jjl wrote: > > > Example is as follows: > > > > The breaking strength of a fiber is required to be at least 150 psi. > > 150 pounds per square inch? That is not only inconvenient to measure, > as it involves computing cross section as well as the tension under > which it breaks; it's also pretty pathetic for anything I'd classify as > a "fiber", let alone bother testing. > > I'd guess cooked spaghetti (_al_dente_, not cooked to mush) might come > in a bit under that figure; just about any string would be a lot > stronger. As an experiment, I just rolled and twisted a 2-yarn cord out > of Kleenex, about 1/8" in diameter; while the length does not afford a > really good grip, I can't break it with my bare hands and would estimate > a lower bound on the tensile strength of 25 lbs. That's about 2000 psi > right there. > > Ah, real-world examples...Reminds me of one in a locally-written high > school textbook that involved Anne [all problems in modern K12 textbooks > must contain a proper name] riding on a Ferris wheel with radius 6m that > went around once every 4 seconds. Quite a ride - the seats would have > been upside-down at the top! > > -Robert Dawson -- Jay Warner Principal Scientist Warner Consulting, Inc. 4444 North Green Bay Road Racine, WI 53404-1216 USA Ph: (262) 634-9100 FAX: (262) 681-1133 email: [EMAIL PROTECTED] web: http://www.a2q.com The A2Q Method (tm) -- What do you want to improve today? . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
