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From: TomGee on 28 Sep 2005 11:13 Randy Poe wrote: > TomGee wrote: > > Randy Poe wrote: > > > Are you going to say F = dp/dt doesn't use a derivative? > > > > > > > > It is a derivative of the force of momentum at a given moment, > > We call p the "momentum", not the "force of momentum". There's > a good reason for that (below). > > > and it can have derivatives of its own too. > > Yes it can. So? > > > Anyway, you have sidetracked us > > enough. You have failed to argue convincingly or logically > > Well, I did argue LOGICALLY, pointing out that F can't simultaneously > be equal to p and dp/dt. But as you said above, LOGIC is > not, for you, CONVINCING. You don't like logic. You don't > believe in it. So I concede all arguments to your impervious > irrationality. My puny logic is no match. > > You're still arguing logically, but about the wrong thing. > > > > against my > > ideas about motion, so let's hear some of your ideas, if you have any, > > and let me show you where you're right or wrong. > > OK, here's one. A moving object with a given momentum p might > cause either a lot of force or very little force in coming > to a halt and reducing its momentum to 0. That's why it makes > no sense to say "momentum is force". > > No sense to you, obviously, but it does to those who use the term to mean a force. In one of my posts yesterday I explain how momentum is the ame thing as force. > > > Example 1: I'm in a car, moving at 60 mph. I hit a brick wall. > My momentum goes to 0 in a few milliseconds. The forces on > me are huge. I'm dead. > > Example 2: I'm in a car, moving at 60 mph. I hit a pile of snow. > My momentum goes to 0 over the course of perhaps half a second. > The forces on me are small. I'm unharmed. > > Even easier to analyze: something coming to me. A baseball is > pitched to me at 40 m/sec (90 mph). It has a given momentum. > How much is the "force of that momentum"? > > Example 3a: I catch the baseball in my glove. My hand might > sting a little, but no damage. > > Example 3b: The baseball hits me in the chest. It breaks > ribs. > > The correct analysis of these situations is to calculate > dp/dt. > > Okay, but that is not the topic in discussion here. You're locked into a topic from some other thread where there is an ongoing discussion about how to analyze situations like your examples above. > The very same momentum will exert very little force > > But a force nonetheless. But tell us too just how a quantity can exert any force at all? And doesn't it take a force to exert a force? > > > if the time derivative can be kept low, which is done by > having soft materials which stretch out the deceleration > time. Even the difference between hitting sand or snow > (say 100 msec) and hitting brick (on the order of 1 msec) > is enough to make a difference of a factor of 100 in the > "force of the momentum", the difference between life and > death. The amount of momentum doesn't tell you the force. > How fast it changes tells you the force. > > But here in this thread we are not seeking the force. You're weird - you extapolate inferences from statements that have no relation to their context. > > > A bullet might only weigh 4 gm. A .004 kg bullet going 1000 m/sec > has a momentum of 4 kg-m/sec. A baseball weighs 0.145 kg > and goes 40 m/sec when thrown by a good pitcher, so it has > a momentum of 5.8 kg-m/sec. > > If the momentum is a force, then the baseball carries more > force than the bullet. Which one would you rather have hit > you in the chest? > > > What do I claim? I claim the baseball is better, because by > the dynamics of the situation dp/dt is much smaller even though > p is almost 50% larger than the bullet. > > Reference for my stats: > > Mass of baseball: > http://hypertextbook.com/facts/1999/ChristinaLee.shtml > > Mass and velocity of bullet: > http://hypertextbook.com/facts/2000/ShantayArmstrong.shtml > > - Randy
From: Randy Poe on 28 Sep 2005 11:51 TomGee wrote: > Randy Poe wrote: > > Well, I did argue LOGICALLY, pointing out that F can't simultaneously > > be equal to p and dp/dt. But as you said above, LOGIC is > > not, for you, CONVINCING. You don't like logic. You don't > > believe in it. So I concede all arguments to your impervious > > irrationality. My puny logic is no match. > > > > > You're still arguing logically, Thanks for that, anyway. > but about the wrong thing. Yes, I keep talking about the relation between force and momentum, whereas you keep correcting me that the topic of discussion is the relation between force and momentum, clearly a different thing. Sorry about that. > > OK, here's one. A moving object with a given momentum p might > > cause either a lot of force or very little force in coming > > to a halt and reducing its momentum to 0. That's why it makes > > no sense to say "momentum is force". > > > No sense to you, obviously, but it does to those who use the term to > mean a force. And you've said "every physics textbook" does so, all over the place. You can no doubt provide a quote from a physics textbook where the term momentum is used to mean a force, right? Thereby proving me wrong when I insist that nowhere in physics is momentum used to mean "force"? > In one of my posts yesterday I explain how momentum is > the ame thing as force. It's wrong in physics no matter how many times you say it. > > Example 1: I'm in a car, moving at 60 mph. I hit a brick wall. > > My momentum goes to 0 in a few milliseconds. The forces on > > me are huge. I'm dead. > > > > Example 2: I'm in a car, moving at 60 mph. I hit a pile of snow. > > My momentum goes to 0 over the course of perhaps half a second. > > The forces on me are small. I'm unharmed. > > > > Even easier to analyze: something coming to me. A baseball is > > pitched to me at 40 m/sec (90 mph). It has a given momentum. > > How much is the "force of that momentum"? > > > > Example 3a: I catch the baseball in my glove. My hand might > > sting a little, but no damage. > > > > Example 3b: The baseball hits me in the chest. It breaks > > ribs. > > > > The correct analysis of these situations is to calculate > > dp/dt. > > > > > Okay, but that is not the topic in discussion here. You're locked into > a topic from some other thread where there is an ongoing discussion > about how to analyze situations like your examples above. I'm explaining why momentum is not a force: because knowing the momentum is not sufficient to tell you how much force the object will result on another object. > > The very same momentum will exert very little force > > > But a force nonetheless. But tell us too just how a quantity can exert > any force at all? It can't. I spoke sloppily, trying to speak your language. An object with the same momentum can exert very different forces. The object, in interacting with another object, exerts a force, whether or not it has momentum. > And doesn't it take a force to exert a force? Really not. When the sun exerts gravitational pull on the earth, what "force" is exerting that force? Gravitational force exerts the gravitational force? Or what? > > if the time derivative can be kept low, which is done by > > having soft materials which stretch out the deceleration > > time. Even the difference between hitting sand or snow > > (say 100 msec) and hitting brick (on the order of 1 msec) > > is enough to make a difference of a factor of 100 in the > > "force of the momentum", the difference between life and > > death. The amount of momentum doesn't tell you the force. > > How fast it changes tells you the force. > > > But here in this thread we are not seeking the force. In this thread (how quickly we forget) we are discussing whether momentum is equivalent to force, and I keep emphasizing that the same momentum can result in very different forces. So here's where you say "irrelevant" because once again I point out yet another illustration of why momentum is not a force: same situation, same momentum, different forces. Since this clearly shows momentum is not equivalent to force, it's time for TomGee to declare "irrelevant to discussion of whether momentum is equivalent to force." But everyone else can see a 3-year-old sticking his fingers in his ears and yelling LALALALALA! So tell me Tom: how much force DOES an object with 5 kg-m/sec of momentum have? A lot or a little? - Randy
From: TomGee on 28 Sep 2005 19:21 Randy Poe wrote: > TomGee wrote: > > Randy Poe wrote: > > > Well, I did argue LOGICALLY, pointing out that F can't simultaneously > > > be equal to p and dp/dt. But as you said above, LOGIC is > > > not, for you, CONVINCING. You don't like logic. You don't > > > believe in it. So I concede all arguments to your impervious > > > irrationality. My puny logic is no match. > > > > > > > > You're still arguing logically, > > Thanks for that, anyway. > > > but about the wrong thing. > > Yes, I keep talking about the relation between force and > momentum, whereas you keep correcting me that the topic > of discussion is the relation between force and momentum, > clearly a different thing. Sorry about that. > > No, you keep talking about a derivative of momentum in a futile effort to show that momentum is not a force. And you can't grasp what's wrong with that picture. > > > > > OK, here's one. A moving object with a given momentum p might > > > cause either a lot of force or very little force in coming > > > to a halt and reducing its momentum to 0. That's why it makes > > > no sense to say "momentum is force". > > > > > No sense to you, obviously, but it does to those who use the term to > > mean a force. > > Hey! You cut out my question about you showing us how a quantity can cause a force! > > > And you've said "every physics textbook" does so, all over > the place. > > Is that a fact or is that your opinion based on one of your far-out inferences? Cite the post so that I can check is you're lying or not. > > > You can no doubt provide a quote from a physics > textbook where the term momentum is used to mean a force, > right? Thereby proving me wrong when I insist that nowhere > in physics is momentum used to mean "force"? > > How would that show that "nowhere in physics" is it used that way? You must think physics is all textbooks and nothing else. (Just rolling with your puny logic.) > > > > In one of my posts yesterday I explain how momentum is > > the ame thing as force. > > It's wrong in physics no matter how many times you say it. > > And your support for that personal opinion is...? > > SNIP silly examples > > > > > > > > > The correct analysis of these situations is to calculate > > > dp/dt. > > > > > > > > Okay, but that is not the topic in discussion here. You're locked into > > a topic from some other thread where there is an ongoing discussion > > about how to analyze situations like your examples above. > > I'm explaining why momentum is not a force: because knowing > the momentum is not sufficient to tell you how much force > the object will result on another object. > > > So why do you need to know "how much force the object will result on another object" in order to know that it will be a force that "results' upon it? Now that really makes no sense. > > > > > The very same momentum will exert very little force > > > > > But a force nonetheless. But tell us too just how a quantity can exert > > any force at all? > > It can't. I spoke sloppily, trying to speak your language. > > My primary language is English. What's yours? > > > An object with the same momentum can exert very different > forces. The object, in interacting with another object, > exerts a force, whether or not it has momentum. > > > And doesn't it take a force to exert a force? > > Really not. When the sun exerts gravitational pull on the > earth, what "force" is exerting that force? Gravitational > force exerts the gravitational force? Or what? > > I could argue that gravitation is a fundamental force and we are discussing contact forces, but I am afraid to confuse you all the more with that. So I will answer yes, g-force as we currently know it exerts the g-force. How it does that I can only theorize Dark Matter "graviton" particles. Do you have answer different than mine? > > SNIP more nonsense. > > > > > > > > But here in this thread we are not seeking the force. > > In this thread (how quickly we forget) we are discussing whether > momentum is equivalent to force, and I keep emphasizing that > the same momentum can result in very different forces. > > Well, I can go along with that if you can tell us how the latter precludes the former, since both say essentially the same thing. > > > So here's where you say "irrelevant" because once again I > point out yet another illustration of why momentum is not > a force: same situation, same momentum, different forces. > Since this clearly shows momentum is not equivalent to > force, it's time for TomGee to declare "irrelevant to discussion > of whether momentum is equivalent to force." > > Clearly? Your so-called "illutration" above shows the opposite of what you claim it shows! > > SNIP more silliness.
From: platopes on 28 Sep 2005 20:04 Traveler wrote: [snip] > > It's all in the interactions. [snip] No doubt. Listen, I got a *whack* of questions for ya, but I also got a *whack* of 8mm film to transfer to MiniDV tonight. Also getting tired of scrolling down the tree to find us (). So look for your last post here pasted into new a thread - "Exploring The Particulate Aether". Sound good? p
From: Traveler on 29 Sep 2005 08:49
On 28 Sep 2005 17:04:10 -0700, "platopes" <platopes(a)yahoo.com> wrote: > >Traveler wrote: > >[snip] >> >> It's all in the interactions. > >[snip] > > No doubt. Listen, I got a *whack* of questions for ya, but I also got >a *whack* of 8mm film to transfer to MiniDV tonight. > Also getting tired of scrolling down the tree to find us (). So look >for your last post here pasted into new a thread - "Exploring The >Particulate Aether". Sound good? Sure Mitch. Let's give it a try, whenever you're ready. But you know how these things usually degenerate? ahaha... Louis Savain Why Software Is Bad and What We Can Do to Fix It: http://www.rebelscience.org/Cosas/Reliability.htm |