<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Physics is a science, and like all sciences, it requires the use of large, complicated sounding words to illustrate rather simple things. This allows physicists to feel more like gurus and less like nerds. Essentially, (linear) Kinematics is motion. Motion in a straight line, with constant acceleration. Velocity can change, but acceleration must be maintain throughout the problem in order for kinematics equations to be used to solve it. There are 4 equations it would be best to commit to memory if you want to be good at kinematics (which are luckily almost identical for rotational and linear kinematics, the former being covered quite a bit down the road.) but before we get into them, we need to know what you need to know, aka, what the variables indicate. u: The starting velocity, the speed essentially at which the object you are looking at starts in the problem. Measured in meters per second (m/s) v: The final velocity, the final velocity is the speed after whatever is going to happen to the object has happened, bit it slowing down or speeding up for a set amount of time. Measured in meters per second (m/s) s: The distance covered in the problem. How far it goes over a period of time or acceleration. Measured in Meters (m) a: Acceleration, the speed up or slowing down of an object. Positive for speeding up, negative for slowing down. Measured in meters per second squared (m/s^2). t: The time it takes for the velocity to change from u to v or the time it takes for distance s to be covered. Measured in seconds (s) The four base equations we can manipulate are...s=1/2(u+v)tv=u+ats=ut+1/2a(t^2)v^2=(u^2)+2as So, if you drop an object off a 50 meter build and want to know what speed it will be going the instant before it hits the ground, you'd find out what values you have and what equation to use.You have s, it being 50 metersYou have u, being 0 m/sYou have a, as the value of acceleration due to gravity on Earth is 9.8 m/s^2 .You want v.Looking at the above equations, you would input all of those values into equation four, to find v. v^2=u^2+2asv^2=0^2+2(9.8)(50)v^2=245v= ~15.65Because v is a velocity variable, you know the units will be in meters per second.... ****Note that all of linear kinematics and most of physics at the high school level ignores air resistance***** <br />Posted by votefornimitz</DIV></p><p>The dictionary definition of kinematics (quite accurate) is " a branch of dynamics that deals with aspects of motion apart from considerations of mass and force". Thus linear kinematics is usually construed to mean motion in one dimension, whether at constant velocity or not. The reason that your high school class is focused on the case of constant acceleration is two-fold. First, the case of a falling object, relatively close to the earth is one of constant acceleration. Second, by limiting consideration to constant acceleration, you do not have to use calculus to do the computation. You simply apply the algebraic formulas that you have quoted.</p><p>An unfortunate aspect of that approach is that you are forced to memorize the equations of motion. If the calculus were available, then memorization would not be necessary since the equations of motion can be derived with almost no work from the assumption of linear motion and constant acceleration. In fact the origin of calculus itself is in mechanics and the application is straightforward.</p><p>The development of calculus by Newton goes something like this. Once upon a time in a land far far away there live a man called Tycho Brahe and his faithful servant Johanne Kepler. Tycho was quite wealthy and spent his time accumulating a vast amount of data on the motion of the planets. Kepler was quite clever and analyzed Tycho's data exhaustively. He noticed a regularity in that data, and purely from an empirical point of view developed a set of laws of planetary motion. He noticed that the planets moved in eliptical orbits and did so in such a way as to sweep out equal areas in equal time. Newton, A VERY CLEVER GUY, wondered why such laws might be true on a more fundamental basis. To explain Kepler's laws de developed the theory of universal gravitation, then formulated laws of motion in what we would today call differential equations. In order to both formulate and solve differential equations he was forced to invent calculus. Stir these together and add in the notions of mass force and momentum and, voila, you have Newtonian mechanics -- the centerpiece of classical physics and one of the great successes of the human mind. Newtonian mechanics is really simplicity itself -- all of the theory of classical mechanics is summed up in three very simple laws, and little bit of mathematics.</p><p>Now as to your statement that "Physics ... requires the use of large, complicated sounding words to illustrate rather simple things." Reality is quite the contrary. Physics has always sought to explain the world in the simplest possible terms, and simplicity is the hallmark of the best physical theories. Einstein spent his entire life in the search for simplicity. His special relativity is based on the astounding simple notion that the speed of light in a vacuum is a constant, independent of the reference frame. From that astoundingly simple assumption came one of the great theories of physics, one that upset the Newtonian apple cart. General relativity is, at its base, just as simple -- gravity and acceleration are indistinguishable.</p><p> When you run across so-called scientists who complicate things unnecessarily be skeptical. Complicaton can come from humble beginnings and be appropriate at times, but it can also come from an attempt to obfuscate ignorance. Physics is at the core simple in nature. And to quote James Rutherford "All science is either physics or stamp collecting." Stamp collecting can appear to be quite complicated, but that is due to lack of fundamental principles and deep understanding.</p><p> </p><p> </p> <div class="Discussion_UserSignature"> </div>