Motion
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From: TomGee on 19 Sep 2005 01:31 What good would that do you when you don't even know who said that.
From: Don1 on 19 Sep 2005 06:42 Herman Trivilino wrote: > "Don1" <dcshead(a)charter.net> wrote ... > > >> That's why a formulation such as yours is not relevant to these cases. > >> > >> > Not to mention that the Prowler is a unique automobile. > >> > >> But, you did mention it, didn't you? > >> > >> And, in regards to the context in which I brought it up, it is in fact > >> not > >> at all unique. Most, if not all, automobiles speed up with an > >> acceleration > >> that is larger in the beginning of the time interval in which they speed > >> up, > >> and smaller towards the end. > >> > >> Therefore, anyone who attempted to use your formulation to describe their > >> motion would get results that are, to a very large extent, wrong. Wrong, > >> that is, in the sense that the distance travelled by them would be, to a > >> very large extent, larger than the distance calculated using your > >> formula. > >> > > Did you see the example problems that I gave for a car starting from > > rest. and the same car starting from 15 mi/hr; where both traveled for > > 20 seconds? > > I not only saw them, I quoted the first one back to you when I explained, at > length using the example of the Plymouth Prowler, its flaw. > > And, as I said, you could improve on your formula, apart from fixing it so > that each term has the same units, by adding a third order term. Would like > me to do that for you? > > Yeah. Then maybe I'll know what your talking about. > > ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- > http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups > ----= East and West-Coast Server Farms - Total Privacy via Encryption =----
From: Don1 on 19 Sep 2005 08:24 Herman Trivilino wrote: > "Don1" <dcshead(a)charter.net> wrote ... > > >> > 3) Resultant motion is the algebraic sum of inertial motion and forced > >> > displacement, and can be written mathematically as d/t=l/t + s/t; or as > >> > d/t=l/t + (a/2)t^2: > > Do you not see that d/t and l/t are terms that have units of velocity, and > (a/2)t^2 is a term that has units of distance?! > > >> I thought my example of the motion of the Plymouth Prowler made it clear > >> to > >> you that this formulation gives results that don't match the way cars > >> really > >> move. > > > These motions are just the basic premises, or postulates. > > I don't understand the relevance of this statement. Are you saying that, > since they are just basic premises or postulates, they don't need to match > what's observed? > > > All actual > > motion is affected by various forces such as the power source and all > > kinds of friction. > > That's why a formulation such as yours is not relevant to these cases. > > > Not to mention that the Prowler is a unique automobile. > > But, you did mention it, didn't you? > > And, in regards to the context in which I brought it up, it is in fact not > at all unique. Most, if not all, automobiles speed up with an acceleration > that is larger in the beginning of the time interval in which they speed up, > and smaller towards the end. > In the beginning when grampa starts pushing grandson on a sled the acceleration increases until grampa can't keep up; then as the acceleration lets up grampa jumps on the back for a ride down the hill. A drag racer starts rapidly, burning rubber as it accelerates, then as the tires gain purchase the engine is slowed down with a corresponding reduction in acceleration. My buick seldom spins its wheels unless its slippery. Don > Therefore, anyone who attempted to use your formulation to describe their > motion would get results that are, to a very large extent, wrong. Wrong, > that is, in the sense that the distance travelled by them would be, to a > very large extent, larger than the distance calculated using your formula. > > Apart from fixing the mistakes I mentioned above with the units, you might > consider adding a third order term. It would get you closer to agreement > with what's observed, assuming that's your goal. > >
From: Sam Wormley on 19 Sep 2005 10:24 Don1 wrote: > > Yeah. Then maybe I'll know what your talking about. > Unlikely Shead--You've *failed* to understand Newton's three laws of motion and that is *indicative* as to why you never understand any physics, as is *documented* in your posting of the last many years. Newton's *First* Law http://scienceworld.wolfram.com/physics/NewtonsFirstLaw.html Also called the "law of inertia," Newton's first law states that a body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an external force. Newton's *Second* Law is about "inertial mass" http://scienceworld.wolfram.com/physics/NewtonsSecondLaw.html A force F acting on a body gives it an acceleration a which is in the direction of the force and has magnitude inversely proportional to the mass m of the body: F = ma Newton's *Third* Law http://scienceworld.wolfram.com/physics/NewtonsThirdLaw.html Whenever a body exerts a force on another body, the latter exerts a force of equal magnitude and opposite direction on the former. This is known as the weak law of action and reaction.
From: Herman Trivilino on 19 Sep 2005 22:12
"Don1" <dcshead(a)charter.net> wrote ... > In the beginning when grampa starts pushing grandson on a sled the > acceleration increases Right. Ok. So, the acceleration is not constant, but it's still equal to the ratio of the net force to the mass. The net force is not constant, is it, Grandpa? The formula for displacement that gave us, where the displacement is the sum of two terms, (v_o)t and (1/2)at?, won't give us the sled's displacement. It's a formula that gives results that don't match what's observed. It may fit your notion of how things ought to be, but it won't make for good, or even acceptable, physics. ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |