If there had been a smiley icon here, people would have read this without thinking that you are an imperious snot. (no icon)
Bob
If there had been a smiley icon here, people would have read this without thinking that you are an imperious snot. (no icon)
Bob
See what I mean Phil ? :-) ...lew...
Larry Jaques wrote: ( the whole discussion sniped )
Yes probably but maybe the jerk should be capitalized. :-) ...lew...
Had a bit of a personal go-around with this one...
My education is in physics and I'm tolerably familiar with how it "really" works, centripetal acceleration and all of that... But, back in high school, we were taught all about centrifugal force, etc. I got my pilot's license and ultimately became a flight instructor. Now, the FAA (at least back then and probably still) speaks of centrifugal force. And that is the way we were expected to teach it, even though I knew it was wrong.
Years later, I had a go-around with my boss after I'd used the word, "mass," in a technical manual I'd written. He insisted, despite his being a senior engineer (admittedly electrical, not mechanical) with all the necessary degrees to back it up, that the proper term was "weight."
I've spent a lot of time informally teaching electronics to various people and learned early on the difference between teaching on a "technician" level and on an "engineering" level. Generally, the kicker that decides the level to use is whether or not the person understands the calculus... But it is often explanations must be used that are not quite correct simply because the person does not have the background to understand the correct one and the "almost right" one works well enough for his purposes.
Moral of the story: If you're talking to someone who has had engineering level calculus and physics, you talk about centripetal acceleration. But if the person is running on high school algebra and physics (which he might know very well), you'd do better to stick with centrifugal force...
Jerry
So then, explain what the force is called that pushes outward against the the inner side of the curve of the rail as the train goes around the curve.
None. The force is the rail pushing IN against the wheel. The train wants to go straight, but the rails force it to turn. Really, unless you're running some numbers, the fight over centrifugal vs. centripetal force is pointless. Call it whichever, and everyone in here is smart enough to figure it out.
One last time: See Newtons second law. There is absolutely NO force acting outward along a radius of the circular path. PERIOD.
Phil, see you can't win. Folks just wont read a physics text. ...lew...
B.B. wrote: Call it whichever, and
And if i call a mill a lathe would you understand what I meant? "Ionly know what you said, not what you meant" ...lew...
And then we wonder about the "education system". When people who know better just "let it slide" (give in to the "dumbed down" attitude of the rest) Is it any wonder things keep on getting worse and worse? Calculus isn't needed to solve most circular motion problems at least the first half of Physics 235 at Penn State in 1953. This could get almost as bad as a recent thread on gun control. :-) ...lew...
Probably not, but few if any of us grew up calling lathes mills or mills lathes, whereas most of us were introduced to centrifugal force before centripetal force and most know how to swing their thinking back and forth between the two. If I were trying to teach a class of kids I'd be more adamant about proper terminology and accurate physical models, but since I'm talking to adults I try to simply adapt to whatever term they prefer.
"Jerry Foster"
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You hit the nail on the head, Jerry... Sometimes I just can't resist rattling that cage once in a while though......it can be such fun..;>) Phil
Actually Wrong...
You need to specify the frame of reference before making blanket statements like that.
There is no outward force acting on the flanges of the locomotive wheels.
There IS an outward force acting on the rails.
F=MA still involves an F :-)
Mark Rand RTFM
I guess they never got to Newtons third law. I'm glad I didn't get into the cetrifugal and centripedal forces caused by the acceleration, deceleration and friction as the train goes around a curve.
John
You're taking too much of a "macro" view of all of this. Learning is largely a spiral. You go around in ever widening circles. When subject matter is first introduced, it is often necessary to use very simplistic explanations. You can't, for example, even use algebra in a seventh grade science class. Later, when students have acquired more background, you can tell them that what they were told in grade school (jr. high, high school,
100 level classes, etc.) was a little intellectually sloppy and give them a more rigorous understanding. And the process is repeated. So, even though a person may have learned what was taught quite well, the sophistication of his knowledge depends heavily on how far down the educational road he traveled. This is not "dumbing down" or "letting it slide." This is the way practical education works.Jerry
Engineers embrace centrifugal force when it simplifies problem solving. If you insist on making observations from a purely Newtonian (inertial) frame of reference, then it's fair to say centrifugal force and the Coriolis force do not exist. If you take a more pragmatic view and make your observations from the most convenient frame of reference, then centrifugal force and the Coriolis force are perfectly acceptable.
I just checked my freshman physics text (Resnick & Halliday), engineering mechanics text (Beer & Johnston) and Mark's Handbook. They all define centrifugal force in a rotating frame, with varying degrees of explanation of CF's relationship to pure Newtonian mechanics, but without apologies.
Ned Simmons
Must work that way for teachers also. One in Dallas has failed her certification test 56 times in 14 years.
--Andy Asberry--
------Texas-----
Here's my favorite take on the question:
That's it in a nutshell, eh?
Ned
The only problem with it is that Bond always manages to escape somehow. But then, the Bond who always manages to escape is never a mindless pedant like this one.
But it's a force, not an acceleration. The two don't even have the same units. One might speak, for instance, of a centrifugal force of 100 Newtons generated by a centripetal acceleration of 3 meters/second^2. Both numbers can be of interest.
Halliday),
Mark's Handbook.
frame, with varying
Newtonian
escape somehow.
mindless
"centripetal acceleration."
have the same
force of 100
meters/second^2.
Perhaps someone would care to explain how the magnet placed on the rim of a flywheel came off as the wheel increased rpm? Could it be that the increasing inertia of the magnet exceeded the magnetic pull of the magnet? Or has a mysterious force appeared out of nowhere to "throw it off" ? heh heh heh .............;>) Phil
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