even more than before physics?
954242
change in momentum = change in mv = \n845 kg * 100 km/h = 845 N s^2/m * 100,000 m / 3600 s =\n(84,500,000 / 3600) N s = 23,472.22 N s\n\nF = m a\nAvg. a = (100,000 m/3600 s) / 0.9 s\nAvg. a = 30.86 m/s^2\nF = m a = 845 kg * 30.86 m/s^2 = 26,080 kg m/s^2 = 26,080 N\n\nWhat exerts the force? \nWell, it depends on what is meant by the question.\nI think the best answer is that it is the road surface that exerts the force.\nIf you stand in front of a wall and push against the wall, what exerts the force that pushes you backwards? Arguably, it is YOU that exerts the force. But I would say that the wall is pushing against your hand (i.e., it is resisting your push, resulting in a force in the direction that you are moving (backwards). By analogy, the road surface pushes the car forward at the same time that the car's tires are pushing backward against the road.
79420
Hey babygurlgonnaloveonu you have asked what is totally QUESTION NUMBER ONE in physics. It's an exciting question which many teachers secretly don't understand and so their students get this hazy idea and kind of go thru the motions. \n\nWow, it is so basic, that it took a super-genius, I mean way smarter than Einstein, to figure it out. A good old farm boy, astrologer, magician & alchemist, religious fanatic, mathematician and all around kook. Yep. Sir Isaac Newton. You gotta wonder what kind of parents would name their kid "Sir"\n\nWell we all know what a force is, it is a sort of push or pull -- think of it as something that changes or *tries to change* the motion of stuff.\n\nNewton first figured out that if you leave a thing alone, or if the pushes and pulls on it cancel out, then it will sit there like a lump. Like those drivers wearing hats, and like sit there after the light has already turned green two minutes ago. \n\nOr else a thing  will keep moving in the same straight line direction and speed  like those drivers wearing hats who go 40 mph on the expressway with their turn signal blinking on and on. This is known as "THE HAT LAW".\n\nAll was well until he noticed that things move faster in an amount equal to how much you bully them or push them around. Twice the force, twice the fasterness and fasterness (also known as acceleration). This is called the "YOU BIG BULLY LAW".\n\nThen he discovered a fly in the ointment. His HAT and BULLY laws didn't really explain all that much. Something was gumming up this beautiful theory. We call it MASS and it is still an unknown mystery as to what it really is. So we vaguely call it the amount of stuff or matter in a thing. \n\nSo he found out that for a certain force the faster-isity (acceleration) is cut in half if you double the mass. The bully has to push twice as hard to fasterize two little kids. So he was like "I'll just add that in, and all will be cool". The "YOU BIG BULLY LAW" and "THE HAT LAW" totally did it all. Wa ta da babee!\n\nBut then Newton had a road accident. He was gunning his Harley over London bridge at like 250 when a bug  hit him in the mouth and knocked out one of his wooden teeth. He was all "Why am I so in pain?". And the bug as it squooshed said "Help! I'm a bug!"\n\nSo spitting out the splinters of his wooden tooth and the splattered bug, he had this revelation. He realized that because he was moving so fast, and the  bug slowed down so fast, that even a eentsy mass like a bug was like taking a hammer to his tooth. \n\nHe noticed that the force was equal to the mass of the bug times the speed of impact all happening in a brief moment. Since Newton spoke Latin (he  was the love child of Joe Newton and an Italian governess) he wrote "Fastus buggus ina momentum hurtus like crazy." Today we call this "momentum". It is just "mass times speed" or "force times a small moment of time". \n\nAnd he realized that the bug smashed up his tooth, but also that the bug was squashed (like a bug) because they were trading the EXACT same amount of momentum. The force on the tooth by the bug in the moment of time was PRECISELY equal to the  smacko-ing the tooth used to stop the bug dead. \n\nHe said "Hey, like he broke my tooth, but I killed him soooo dead!" He did the math and found that the force of the bug on the tooth was equal to the force of the tooth on the bug! \n\nNo way did the two equal forces cancel, after all, his tooth was hammered to splinters, and the bug was flattened. They were equal and opposite, but since one was on the tooth, and the other force was on the bug they did serious damage! Today we call this the "HELP I'M A BUG" law.\n\nNow our man 'Zack was all set. He wrote down his three laws:\n\nTHE HAT LAW (beeep! beeep! Move it Hat Guy!)\nTHE YOU BIG BULLY LAW (betcha can't kno
663488
Do you mean more than it already has???
756937
for sure.\n\nbible is descriptive.... quantum physics is a snap.\n\naren't you glad..\n\nthat way its cover 11 or 12 diminsions where you only think in 3 or 4.
553845
Here is the problem...\n\nThe more you study things, the more questions you have about them. Even Einstein died without fulfilling his wish to develop the unified field theory, unifying gravity with the other three known forces.
475210
more than ur and mine
665655
Internet has enough of a force of its own to do that. Seems like the gravitational force of the net is more than that of the world.
4008
the formulas are what convince me.  I've had to derive so many complicate formulas myself, and most of them, especially mechanics formulas can be proven, such as measuring a quantities, solving for a missing variable, then doing an experiment and getting the same answer.  This is too much to be a coincedence or something.  Most theories and things are developed before formulas and actual mathamatical relationships are found, then they find them and it all fits together nicely.  Even with reletivity and things with spacetime, there are a lot of concrete formulas, and once you have the satisfaction of deriving them yourself from previously proven formulas... it all clicks nicely, that's why im a physics major, curiosity about everything like this.  I guess human perception can be valid once connections start being made between things, because when ideas are incorrect, they really don't connect to other things very easily.
530388
In more ways than one.
771712
You ask an interesting question, actuallly.  The techniques used to answer this question keep getting refined and the equipment keeps improving, which allows scientists to make better estimates on this number.  Current estimates have it at roughly 125 billion.  Now, new technolgies may change this estimate - as knowledge improves, scientists reserve the right to change their minds.  :)
903568
Impossible to compare. Both were the preeminent scientists of their generations. Einstein certainly knew a lot More, but he had the advantage of having Newton & many others shoulders to stand on.
617691
Many physicists go into information technology professions. I have seen quite a few, ranging from PhDs and bachelors, working in IT consulting, teaching, programming, and all sorts. It seems that stuff learnt in physics lectures can be translated into IT work too.
1042790
It seems research on this has continued. Still sounds very preliminary though - experiments on small models or paper planes ;)  But maybe you'd like to check the links.
313282
You are talking about a point in time when the physical laws that exists today were not relevant.  We suspect,at that time, that there were 11 different dimensions, but we don't really know.  Also, it was not infinite mass, or even infinite energy (such concepts are just that, only concepts) it was a potential well of energy that breached the edge of the well, so to speak.  The massive influx of energy later cooled to form mass, like electrons, protons and nuetrons.  These formed Hydrogen which formed the stars which made all the other elements.
322523
The fact that we can observe only four dimensions seems obvious, but that doesn't mean that there are not more.\n\nAs an example: the sea as seen from an airplane looks pretty flat and seems to have two dimensions only. But as the airplane looses height, the waves can be distinguished and we see that the see surface in reality is three-dimensional.\n\nThe same might be true for the universe: it could be that more dimensions are present, but we don't see them as they are tiny, too small to observe from our human scale.\n\nTheories that suppose the existences of more dimensions have been proposed.\n \nThey were invented because we are not so happy about the models we use now. For instance, there are four forces in nature. Three of them -electromagnetism, the strong nuclear force and the weak nuclear force- have been combined into one force that has three manifestations at our energy scale.\n \nTo model the fourth force -gravity- Einstein invented general relativity.\n\nThe problem is that both theories are incompatible. Calculations done with them in the region where they overlap, notably when we go back in time to the Big Bang, give different results.\n\nThat is ...embarrassing.\n\nSome of the newer theories, like superstring and M-theory, try to overcome these problems. The price to pay is the assumption of extra dimensions.
854690
More math than I can remember.
874570
NO!!  If people would stop (mis)quoting half-remembered precepts here, and do a spot of THINKING, instead, we might get somewhere.\n\n1.  If a moving spherical ball directly hits an identical free, stationary ball head on in an elastic collision, the moving ball STOPS, and the previously stationary one heads off with the original velocity of the other.  So ALL of the moving ball's K.E. has been transferred to the other ball.  \n\nHere are two ways to see this:\n\n1a.  The device known somewhat indelicately to British schoolboys as "Newton's balls" (but in squeamish America as "The Swinging Wonder") provides an excellent table-top demonstration of this.  Most undergraduate physics instructors must haul this out from time to time.\n\n1b.  You can easily solve it analytically, but a thought experiment will also demonstrate it.  In the originally stationary ball's frame, let the other ball approach with speed v.  Now shift (with an appropriately directed speed of v/2) to the frame in which the two equal balls are simply approaching each other, each with a speed in this frame of that same v/2 (oppositely directed, of course)!  Clearly, from the symmetry of the situation, they'll bounce off each other with the same (oppositely directed) speeds in this frame, still of v/2.  Now go back to the original frame: the previously moving ball is now completely stationary, while the originally stationary one is haring off with speed v.  (You may need to make little sketches of what is happening as viewed successively from each of these frames, to see this; I admit that that's what I did.)\n\n2a.  A similar approach can be used to solve the general case for an arbitrary ratio of masses, m (initially moving)/M (initially stationary).  Hint: have the balls approach one another in their center of mass frame with equal but opposite momenta of mv and  MV.  They'll clearly bounce off one another in such a frame, retaining the same values of their respective (but now oppositely directed) speeds.  Then you can do the other frame-jugglings from there. \n\nHowever, this analytical approach, done accurately, is a tedious mess.  So, to appreciate the general problem more physically, consider just the following:\n\n2b.  The case of m << M.\n\nConsider the "equal but opposite momentum" frame for these two balls, in which MV = mv.  This means that if ball M is VERY MASSIVE, the speed it will have in such a frame, V = (m/M)v; that is, it's VERY SMALL compared to little puny m's high speed.\n\nSo, transforming to the frame in which M itself (the big guy) is initially stationary takes only a speed shift of O(m/M)v.  (In fact identically so.)  This only affects the speed of puny m minutely, so m's initial K.E. is still of order O(m v^2).  (There's no need to do picky constant book-keeping for these purposes.)  \n\nNow after the collision: In the original frame, Big M is now moving (and in fact at 2V if you think about it.)  But, being loose about the constants, M's K.E is only O(MV^2).  \n\nSo, the ratio (m's K.E.)/(M's K.E.) ~ (mv^2)/(MV^2)\n\n= (m/M)(M/m)^2 (since mv = MV)\n\n= M/m.\n\nBINGO!  The little bugger still carries by far the larger amount of the kinetic energy.  The massive ball (i) moves sluggishly, and (ii) because  K.E. involves both mass but also the SQUARE of the speed, the TWO POWERS of (small) speed more than cancel out the effect of its (large) mass.\n\nThis is a well-known fact in particle collision theory, that little particles basically bounce off big ones.  \n\nYou could also say that it's well-known in "space billiards": when spacecraft head close to Jupiter to receive a "gravitational sling-shot effect" that sends them off to the outermost planets.  \n\nIt's more complicated because of 3-D effects there, but analogous frame-shifting methods can be used to show that the spacecraft can pick up considerable speed AND change