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Kinematics: Which Equation to Choose

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part of video that applies to us is 5:28 to 7:53

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laying here from Malaysia Versi. Com MCAT and in this video I'm going to show you how you can quickly and easily determine which kinematic equation to use when faced with an that physics problem for details tutorials on the individual topics and Concepts including work through practice problems catch my entire series on translational motion by visiting my website late for sciatic on MCAT physics you may see many different forms of the kinematic equations but if you understand them and work through them you'll recognize that these are the four main equations that you have to know for details right down on these equations and more grab my MCAT kinematics on my website labor said accomplish and Pat visit them one at a time to show you how you can rewrite them and understand the different forms of the same equation that you'll see when was the first one noticed that we have X finals exponential plus VT if your problem starts at x equals 0 you may drop the X and simply have the form X is equal to VP you may also see this written as X is equal to V average x t we want to take the average of A and B will have a surplus T over to and that'll be the average to find the average velocity will have velocity OnePlus philosophy to over to the average assuming have no acceleration in the X Direction your V1 and V2 should be the same and therefore your V average is your velocity equation will look at is the final equals the initial + 80 this actually comes from equation for acceleration because acceleration is equal to the change in velocity over the change in time or simply T that's Delta means the change or final minus initial and that comes from the formula acceleration is equal to minus the initial over T if we want to isolate V final from this equation we multiply both sides by tea and then was the initial to the other side rewriting this equation we get the final is equal to special + 80 in this situation if you're starting at a velocity of zero velocity drops out and that is the simplified version final is equal to 80 or emails to see the simply as V is equal to the final reason I want to look at is the final squared is equal to the initial squared plus to a Delta X for this equation Delta X is your total displacement so you can also write it as to a x x final - x initial when you find that changing apps to get a distance to see this equation in correctly written with a d where the D represents the distance which implies your displacement your initial velocity is zero. Drops out giving you a simplified version of the equation V final squared is equal to 2 a Delta X or even more simplified V squared is equal to 2 AC system of equation especially don't like when we're not specifying V final that you may see it this way so recognize that it is the same thing and last but not least the equation that seems to cause the most confusion is Delta exes the initial t + 1/280 squared there are many ways to represent this equation and well they say the same thing because they don't look the same a lot of students get confused so I want to show you how to relate the different forms to make sure you can get confused if you see the sign or MCAT the first confusion comes from the way this form of the expression is written sub I needs the initial release of f is V final but there's another way to write this if you have V with a little oh that's be not or the starting velocity which is the same thing as the initial velocity do I write this as V not see I'm talking about the same expression another point of confusion is the x value Delta x mean X final - x initial suicide rewrite this as X final - x initial and then I want to solve for just X final I have to bring X initial over to the other side + x initial for both sides and we write the equation as follows X final or simply X is equal to my X initial + the initial t + 1/280 squared this is just a longer way to write it and most likely if you working through an MCAT question where you're given velocity and acceleration assuming that you start at x equals 0 and I dropped out of the equation and finally one more point of confusion is that I've often seen the equation written as a is equal to the initial C + 80 squared / 2 this throws off a lot of students anytime you have a value or an equation over a number meaning divided by a number you can pull that number out and multiply it just buy 1/2 in this case which is how we get the 1/2 80 squid so hopefully now you understand how to relate the different versions of the equation which brings up the next question how do you know which equation to use in any given problem I want you to analyze these equations with me and recognize that we have four main units that were looking for anytime we have a final and initial were only looking for the final so we have unit 4 x 4 displacement Travelocity specifically be final we have a unit for acceleration and we have time every equation given has three out of the four units the first one has xvnc but it does not have Excel duration the second one has the final word ignoring the initial a and see what it does not have displacement or X the third one has the final it has acceleration and displacement but it does not have time and finally the last one has displacement we're ignoring the initial remember we're looking for the final hazard unit we have acceleration we have time we do not have velocity Final in referring to these equations say it has the three given where we can say it is missing so for example the first equation is the acceleration Independence equation the second one is displacement independent and so on an Ematic question you'll be provided with two units and asked us all for the 3rd so the way you can tell which equation to use is identify the two units that you're given the unit that you're asked to solve and then see which equation has those three units for example if I tell you to sell for total distance and I give you velocity and time I'll see that I'm asked for distance I'm given velocity and time but I'm not given acceleration or tilt of sulfur acceleration so why would I consider unit that I really have no use for that situation we saw acceleration independent equation to keep in mind everything here is written out for the X component but if you have why you can swap it out X becomes Y and acceleration becomes the acceleration of gravity at 10 second squared keeping all of this in mind I want you to go back to my kinematic videos where they walk you through it examples of velocity displacement acceleration of Free Fall projectile motion and I want you to consider the individual problems see how I determine what we're given what we're ask for what we're not ask for and therefore quickly narrow down the equation to use you can find my entire series on translational motion by visit my website late for Sarah, MD physics are you stuck on a specific MCAT topic I offer private online tutoring why focus on your needs to strengthen your individual weaknesses to turn details can be found using the link below or by visiting websites for MCAT tutor are you overwhelmed by the sheer volume of information required for the MCAT are you worried that lack of a proper study plan and low MCAT score will prevent you from getting into medical school my new ebook the MCAT exam strategy a six-week guide to crushing the MCAT will help you formulate a concrete study plan by helping you figure out where you stand now identify your goals and figure out what it takes to reach them and it's yours when you sign up for my email newsletter at MCAT exam strategy.com by signing up for my email newsletter will also be the first to know when I have new videos and can't study guides cheats and so much more the link again MCAT exam strategy. 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Kinematics: Which Equation to Choose

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