Sternjaeger Posted June 10, 2014 Posted June 10, 2014 S! Just a dumb question..When speed is increased the power needed also increases as friction greatly increases as well? Take Bugatti Veyron, it took 1000hp for it to reach 407km/h and 1400hp to reach 430km/h. So wouldn't this apply to planes as well? You get power with colder air but the power is not enough to give a substantial increase in speed as the friction also increases with speed? Am I right or totally lost? Math and physics a bit rusty for me Cars and aircraft have a totally different way of "translating HP into speed". For instance you could throttle back to idle, put your plane on a dive and you'd see a considerable increase in speed with no increased engine power output; if you did that with a car you wouldn't see the speeds you see with an aircraft, simply because the biggest friction factor is caused by your tyres, which incidentally are also the only way for your car to generate "thrust".
Sternjaeger Posted June 10, 2014 Posted June 10, 2014 An increase in engine power due to lower temperature and thereby higher density of the air will result in about the same true air speed (TAS), the speed with which the aircraft moves through the air. It will also result in a significantly higher indicated air speed (IAS), which is actually a pressure difference between the dynamic ram pressure and the static environmental pressure, which is used for the dials in the cockpit. lower temperature doesn't necessarily mean a higher density: you might be at 20,000 ft and have both very low temperature and density. Your indicated airspeed will read significantly lower than your true speed, but as Bongo said unless you have a TAS (generally given by a satellite navigation system), you'll have to rely on what the pitot reading is.
Cpt_Branko Posted June 10, 2014 Posted June 10, 2014 (edited) Acceleration is a unit of distance over time squared. The technique not only works, it is what is taught in the aerodynamic departments of all major universities in the United States. It is where I learned it. Distance over time squared, but in the context above you used it as velocity over time squared instead? If you meant it, and that's how I understood you, as "time to reach a certain speed decreases with the square in net force applied", that just doesn't work out. Edited June 10, 2014 by Cpt_Branko 1
Crump Posted June 10, 2014 Posted June 10, 2014 Distance over time squared, but in the context above you used it as velocity over time squared instead? If you meant it, and that's how I understood you, as "time to reach a certain speed decreases with the square in net force applied", that just doesn't work out. No we are not using velocity. We are using the relationship defined by the math. Force = Mass X Acceleration Force (lb) = Mass (lb/ft/s^2) x Acceleration (ft/s^2) If we hold mass constant, in order to increase force, we must increase acceleration. Therefore, force also has a time squared relationship. It is right there in the math. If we increase Force by 13% (1.13), then we can expect our time to decrease by 1.13^2 = 1.27 or 27%. In other words, the game is modeling the trends of atmospheric effects properly and players just do not understand those effects. We cannot gauge the specific performance found in the game without more information on the atmospheric model.
MiloMorai Posted June 10, 2014 Posted June 10, 2014 Force = Mass X Acceleration Force (lb) = Mass (lb/ft/s^2) x Acceleration (ft/s^2) What is this Mass (lb/ft/s^2)?
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 No, that is just not correct, mass is NOT (lb/ft/s^2), Force can be a measure of Mass over distance but neither have a measure of time, you are falsely bringing the time squared element into the equation, acceleration is a factor of time squared but it stands alone and is not transposed to another part of the formula.
Dakpilot Posted June 10, 2014 Posted June 10, 2014 perhaps seeing as this is a thread for historical data in the developers assistance section, debates over mathematical formulas could be taken to another thread or continued by PM, lets not let this subject continue into prolonged argument and get locked...or is that part of the sport? 2
Crump Posted June 10, 2014 Posted June 10, 2014 What is this Mass (lb/ft/s^2)? http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/slug.html perhaps seeing as this is a thread for historical data in the developers assistance section, debates over mathematical formulas could be taken to another thread or continued by PM, lets not let this subject continue into prolonged argument and get locked...or is that part of the sport? Absolutely. The math is what it is and the developers already know this stuff I am sure.
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 perhaps seeing as this is a thread for historical data in the developers assistance section, debates over mathematical formulas could be taken to another thread or continued by PM, lets not let this subject continue into prolonged argument and get locked...or is that part of the sport? If somebody is going to put maths in a thread it may as well be correct. 1
Crump Posted June 10, 2014 Posted June 10, 2014 No, that is just not correct, mass is NOT (lb/ft/s^2), Force can be a measure of Mass over distance but neither have a measure of time, you are falsely bringing the time squared element into the equation, acceleration is a factor of time squared but it stands alone and is not transposed to another part of the formula. The time does not "stand alone" in any formula but rather defines the rate. It can cancel when the math is solved but it most certainly exist's.
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/slug.html So you add a link that proves you wrong? Weight = mass x g, maybe you understand the concept of weightlessness?.........or maybe not. The time does not "stand alone" in any formula but rather defines the rate. It can cancel when the math is solved but it most certainly exist's. No, acceleration is distance/time squared, there it ends, you do not put the time squared on to mass or force in the formula
Crump Posted June 10, 2014 Posted June 10, 2014 This may make it easier to understand Bongo since you are having trouble putting it together. Let's take this to PM. I can show you how the formula works and all the units cancel to give us the correct units for whatever we wish to solve for in the equation for Newton's Second Law of Motion: F=ma This is not the place to teach basic math and physics.
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 (edited) While the pound force and pound weight are the widely used units for commerce in the United States, their use is strongly discouraged in scientific work. The comparison of the slug and the pound makes it clear why the size of the pound is more practical for commerce. But at the precision obtainable in current scientific work, it is undesirable to have the weight of an object as a standard because the value of g does change measurably at different points on the Earth. It is much better to have a standard in terms of mass. The standard kilogram is the mass reference for scientific work. http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/slug.html Edited June 10, 2014 by DD_bongodriver
Crump Posted June 10, 2014 Posted June 10, 2014 (edited) The unit of mass in the foot-pound-second (British engineering) system, equal to the mass that will require an acceleration of 1 ft/s when subjected to a force of 1 pound. It is therefore equal to 1 lb s ft, 32.1740 pound-mass or 14.5939 kg (O'Hanian 1985, pp. 14 and 96-97). The British Gravitational System (Imperial System) of units is used by engineers in the English-speaking world with the same relation to the foot - pound - second system as the meter kilogram - force second system (SI) has to the meter - kilogram - second system. For engineers who deals with forces, instead of masses, it's convenient to use a system that has as its base units length, time, and force, instead of length, time and mass. http://www.engineeringtoolbox.com/mass-weight-d_589.html For orbital mechanics, the BGS system is not so good but for determining motion and force.....it is very convenient and works very well. That is why it is most common system used in the United States engineering departments for Aerodynamics and Aircraft Performance calculations. All of this a sidetopic. The math is sound and the conclusions correct. The original statement on the subject of the thread holds true and can be see in the mathematical relationships of Newtons Second Law of Motion. The game is modeling the trends of atmospheric effects properly and players just do not understand those effects. We cannot gauge the specific performance found in the game without more information on the atmospheric model. Edited June 10, 2014 by Crump
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 it may work very well when used correctly, but so far I see no evidence of you doing that.
Crump Posted June 10, 2014 Posted June 10, 2014 You present the fact the BGS unit of mass does not work well for determining an aircraft's performance on Mars because the basic unit uses the acceleration of earth's gravity (32.2ft/s^2). Fortunately, the aircraft's performance on Mars or Pluto is not the topic. We just need to know what is the probable performance on Earth. We will just have to agree to disagree. While you see no evidence of it being used correctly I see no evidence you would understand it worked correctly or not. You cannot recognize the importance of rate or the acceleration of gravity in the basic formulation.
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 You present the fact the BGS unit of mass does not work well for determining an aircraft's performance on Mars because the basic unit uses the acceleration of earth's gravity (32.2ft/s^2). I said no such thing, I imply nothing of the sort. Fortunately, the aircraft's performance on Mars or Pluto is not the topic. Yet you bizarrely bring it in to the topic? The rate of acceleration of gravity not part of the formula. Let me explain in SI F=ma F= Newtons m=Kg a=m/s^2 Now lets go back to an earlier post I made Force = mass x acceleration since when was Force^2 = acceleration? Mass is going to be the constant here lets make it nice round figure of 100Kg lets make acceleration 100 flobnerbels (just needs to be a figure units are not relevant) 100kg X 100flobnerbels = 10000N 10000N @113% =11300N 11300N = 100Kg x 113 flobnerbels Acceleration = Force / mass ..........not F^2 113 flobnerbels = 11300N /100kg All very directly related to make the formula work but if we decrease the time by 30% we have increased the acceleration by 43%, lets say something took 100 seconds to reach 100metres = 1m/s, now it takes 70 seconds (30% less) 100/70 = 1.428m/s 1.428 x 100 =142.8 or 143 rounded up 143 143 flobnerbels = 14300N/100..........doesn't seem like a 13% increase in force to me Please explain?
Dakpilot Posted June 10, 2014 Posted June 10, 2014 (edited) ZZZZZZZZZ...... This is a forum for like-minded lovers of WW2 history, aviation, and combat flight simulators. We want this to be a relaxing, enjoyable place to come and talk, learn and teach about our shared interests.In the interests of maintaining a positive, enjoyable forum atmosphere, the moderating team will begin taking a harder line against those few members whom they feel:- consistently cause or involve themselves in threads that generate arguments or ill will.- consistently post in an aggressive, provocative, or antagonistic manner. Edited June 10, 2014 by Dakpilot
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 ZZZZZZZZZ...... This is a forum for like-minded lovers of WW2 history, aviation, and combat flight simulators. We want this to be a relaxing, enjoyable place to come and talk, learn and teach about our shared interests. In the interests of maintaining a positive, enjoyable forum atmosphere, the moderating team will begin taking a harder line against those few members whom they feel: - consistently cause or involve themselves in threads that generate arguments or ill will. - consistently post in an aggressive, provocative, or antagonistic manner. I quite agree, so when somebody decides to start pontificating with pseudo maths I just want to step in and make some sense of it, feel free to add a constructive and decisive solution to the issues being bashed out and I'm sure it will stop.
Dakpilot Posted June 10, 2014 Posted June 10, 2014 (edited) This may make it easier to understand Bongo since you are having trouble putting it together. Let's take this to PM. I can show you how the formula works and all the units cancel to give us the correct units for whatever we wish to solve for in the equation for Newton's Second Law of Motion: F=ma This is not the place to teach basic math and physics. The offer was there.....this is not the thread to pontificate about maths Cheers Dakpilot Edited June 10, 2014 by Dakpilot
Crump Posted June 10, 2014 Posted June 10, 2014 (edited) dd_bongodriver says: lets make acceleration 100 flobnerbels (just needs to be a figure units are not relevant) I think the issue is that units are relevant. In order to be a unit of acceleration, it must be have the basic elements of Distance per Time per Time or shortened to Distance per Time^2. You are obviously an intelligent person bongodriver, so not understand the basic units means you continue to question the results. Unfortunately, instead of the math being a good thing that lends insight into how these airplanes work and achieve the performance expected, it becomes a bunch of gobble-de-gook with the original point lost in the white noise as you continue to question. The community looses with that dynamic. The math is not really debatable. It is correct or not. Trust me, the devs are fully capable of performing this level of math!! This is really tiresome. People have asked to quit it.....so let's quit it...please. PM me if you have questions and I will try to help you understand the math. Edited June 10, 2014 by Crump
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 PM me if you have questions and I will try to help you understand the math. I feel compelled to make you the same offer but it is genuinely more fun (for me) being open and honest about this. No, the units are irrelevant, because they are now a known quantity you only work with the raw figures in the formula, I say the units are irrelevant to highlight the fact that you are incorrectly using time squared in the whole formula. again: F=ma 100kg x 100ms^2 = 10000N 10000N x 1.13 (your increase of 13%) = 11300N A force of 11300N on a mass of 100Kg will give an acceleration of?........yep you guessed it 113m/s^2, that is an increase in acceleration of 13% will an increase of acceleration of 13% reduce the time between points by 27%? Lets see 100m/s^2 in 10 seconds will get us how far? 10^2 = 100 100 x 100 = 10000m 113m/s^2 in 10 seconds therefore will get us 11300m how long does it take to get to 10000m at 113m/s^2? 10000/11300 = 0.884 x 100 = 88.4% of 10 seconds.......oh dear that's a 11.6% reduction in time So, to sum it up for F=ma: It's a concise and sufficient statement of Newton's Second Law of Motion. In vector form (F=ma, bold quantities are vectors) it shows that acceleration and the applied net force are parallel vectors. Keeping the mass constant demonstrates a direct proportion between acceleration and the applied net force. Keeping the force constant demonstrates an inverse proportion between acceleration and mass. And of course, you can navigate with the kinematics equations. Just have your mass and net force handy so that you can calculate the acceleration. http://zonalandeducation.com/mstm/physics/mechanics/forces/newton/mightyFEqMA/mightyFEqMA.html
sturmkraehe Posted June 10, 2014 Posted June 10, 2014 No we are not using velocity. We are using the relationship defined by the math. Force = Mass X Acceleration Force (lb) = Mass (lb/ft/s^2) x Acceleration (ft/s^2) If we hold mass constant, in order to increase force, we must increase acceleration. Therefore, force also has a time squared relationship. It is right there in the math. If we increase Force by 13% (1.13), then we can expect our time to decrease by 1.13^2 = 1.27 or 27%. In other words, the game is modeling the trends of atmospheric effects properly and players just do not understand those effects. We cannot gauge the specific performance found in the game without more information on the atmospheric model. What you call here a "Force" is in fact a force devided by Earth's gravitational acceleration and therefore has the unit of a mass. One might do that but it is imho not helping. Better use SI units which are derived directly from Newton's laws that say: Force (N) = mass (kg)*acceleration (m/s^2) This is the definition of the physical force in its purest form. Your formula is derived from it by deviding this equation by g0 which is completely futile because it does not enhance the information contained in Newton's Law. In fact it seeds confusion because suddenly the force gets the unit of a mass. And we all know that mass is not equal to a force.
Sternjaeger Posted June 10, 2014 Posted June 10, 2014 I was gonna say something about the usual suspect reinventing physics, but I'll limit myself to an IBTL..
Crump Posted June 10, 2014 Posted June 10, 2014 (edited) What you call here a "Force" is in fact a force devided by Earth's gravitational acceleration and therefore has the unit of a mass. Never have I confused slugs with force pounds in F=ma Why would you even think this? You do know that when you do the math operations with the correct units, they cancel leaving you with our pounds of force. Force (lb) = Mass (lb/ft/s^2) x Acceleration (ft/s^2) The result is Force in Pounds. That is another reason why units are so important in physics. Better use SI units which are derived directly from Newton's laws that say: Force (N) = mass (kg)*acceleration (m/s^2) This is the definition of the physical force in its purest form. Which is true but does not negate the validity of the BGS system. Once again, the proportional relationship still exist's. Force (N) = mass (kg)*acceleration (m/s^2) An increase in distance represents a decrease in time at the Square Root of that proportion. You can easily see that in the basic formula for calculating distance covered at a constant acceleration: s = u * t + 0.5 * a * t^2 s=distance covered u= initial velocity a=acceleration t = Time Time is squared to account for the basic relationship of the units found in F=ma, Newtons second law of motion. If you do not square time, then the units will not cancel correctly leaving you with a unit of distance. The relation of distance to time squared holds fast. 100m/s^2 in 10 seconds will get us how far? 10^2 = 100 100 x 100 = 10000m 113m/s^2 in 10 seconds therefore will get us 11300m how long does it take to get to 10000m at 113m/s^2? 10000/11300 = 0.884 x 100 = 88.4% of 10 seconds.......oh dear that's a 11.6% reduction in time That is not even close to how you calculate constant acceleration over time. I am going to start a private topic and invite both Sturm and bongo. Edited June 10, 2014 by Crump
DD_bongodriver Posted June 10, 2014 Posted June 10, 2014 That is not even close to how you calculate constant acceleration over time. I am going to start a private topic and invite both Sturm and bongo. it is precisely how it's done, leave me out of the PM, I don't want to give private tuition without a fee.
Crump Posted June 10, 2014 Posted June 10, 2014 PM is sent. I invited Bongo, Strum, and Cpt_Branko. Anyone else is welcome.
sturmkraehe Posted June 10, 2014 Posted June 10, 2014 (edited) Never have I confused slugs with force pounds in F=ma Why would you even think this? You do know that when you do the math operations with the correct units, they cancel leaving you with our pounds of force. Force (lb) = Mass (lb/ft/s^2) x Acceleration (ft/s^2) The result is Force in Pounds. That is another reason why units are so important in physics. Which is true but does not negate the validity of the BGS system. Once again, the proportional relationship still exist's. An increase in distance represents a decrease in time at the Square Root of that proportion. You can easily see that in the basic formula for calculating distance covered at a constant acceleration: s = u * t + 0.5 * a * t^2 s=distance covered u= initial velocity a=acceleration t = Time Time is squared to account for the basic relationship of the units found in F=ma, Newtons second law of motion. If you do not square time, then the units will not cancel correctly leaving you with a unit of distance. The relation of distance to time squared holds fast. That is not even close to how you calculate constant acceleration over time. I am going to start a private topic and invite both Sturm and bongo. I did not say that your calculation was wrong, Crump. I know that Americans and British are very fond of their system. It has certainly made its proof. It is also twisted. I really recommend SI units because they are more straight forward and closer to the physical phenomena for which this system was developped. You do not need to artificially manipulate the mathematical expression of physical laws by deviding constants in order to obtain the units used for the system like you have to do with Newtons laws in order to be able to express Force in the unit of mass. The SI system also has the advantage that whenever I see a number followed by the unit N for Newton I know that it is a force and I do not need to tell everybody that this is actually a force when the unit is expressed in lb. That is all I'd like to contribute to this particular turn of the discussion Edited June 10, 2014 by sturmkraehe
Sternjaeger Posted June 11, 2014 Posted June 11, 2014 Enjoy your PM guys. what, you're gonna miss a lecture on "my world, my physics"?
DD_bongodriver Posted June 11, 2014 Posted June 11, 2014 (edited) I won't deny I'm fascinated by what the crazy world of Crumpp and his magic physics could bring up but I'm glad he at least heeded my advice and didn't include me on the PM, I'll wait to hear what you lucky chaps have to report on your first day at school. Edited June 11, 2014 by DD_bongodriver
Crump Posted June 11, 2014 Posted June 11, 2014 I won't deny I'm fascinated by what the crazy world of Crumpp and his magic physics could bring up but I'm glad he at least heeded my advice and didn't include me on the PM, I'll wait to hear what you lucky chaps have to report on your first day at school. You were included and several attempts were made......
DD_bongodriver Posted June 11, 2014 Posted June 11, 2014 (edited) Ok, fair enough, just checked and it's there, I didn't get a notification for some reason. Seems a little pointless though as I have already posted everything you need to know here. Edited June 11, 2014 by DD_bongodriver
Crump Posted June 11, 2014 Posted June 11, 2014 I did not say that your calculation was wrong, Crump. The idea of parametric study and proportional thinking is paramount to the study of physics, aerodynamics, and aircraft performance. It is a point that was driven home in almost every class in college. Here is the first chapter from ASCI 310 Aircraft Performance. It is an interesting read. Chapter1.pdf The game is modeling the trends of atmospheric effects properly and players just do not understand those effects. We cannot gauge the specific performance found in the game without more information on the atmospheric model.
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