Phys 201 1nd Edition Lecture 2 Outline of Last Lecture I. Understanding speed, velocity, displacement, and accelerationOutline of Current Lecture II. Basic equationsA. Straight lineB. ParabolaIII. Combined equationsIV. Gravity & FreefallCurrent LectureBasic equations: If you graph an objects movement compared to time, you will come up with one of several kinds of graphs. Depending on what kind of graph you have, you can use one of two equations to represent a function of your graph.For a straight line: This means that the acceleration of the object is constant. The equation that represents a graph of a straight line is;V=V0 + atWhere V=final velocityV0= initial velocitya= acceleration (slope of a line)t=timeFor a parabola: This means that the position of your object does not change at a constant rate, which causes a curved graph. In this case, the equation you would use is;X=X0 + V0t + (1/2)at2Where X= final positionX0 = initial positionV0= initial velocityThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a= acceleration (slope of a line)t=timeWhen given a problem in physics, the easiest way to figure out which equation to use is to sort out whichvariables are given, and which variable you are solving for. For example: An object is moving at an initial velocity of 8m/s. After 3 seconds it is traveling at a velocity of 20m/s. What is the acceleration? In this case, your given variables are:V=20m/sV0= 8m/st=3sAnd you are solving for the variable “a”. Therefore, you would use the first equation; V=V0 + at. The easiest way to do this is to rearrange the equation so that you isolate the variable you are solving for before you plug any of the other values in. Because you are solving for a, the equation would be rearranged to become a= (V-V0)/tWhen you plug in your values, this becomes a=(20m/s-8m/s)/3sTherefore the acceleration of the object is 4m/s2Combined equations:Some problems will leave out two variables that you need to solve for. Because acceleration and time arevariables in both equations, you cannot use either equation to answer a problem that does not at least give you one or the other. If this is the case, you will use the equation:2a(X-X0)=V2-V02 This equation is the simplified form of your other two equations combined. If you are given a problem where you are expected to find both acceleration and time, you will first solve for “a” using this equation. Once you have calculated a value for “a”, you can then plug all of your values into either equation and solve for “t”.Freefall and Gravity:All objects fall with the same downward acceleration of a=9.81 m/s2. The term for this constant acceleration during freefall is “g”(meaning gravity). However, because the object is falling, the acceleration is considered negative, which means we would use -g=-9.81m/s2. We can use any of our three equations to solve for problems involving objects in freefall by substituting a “-g” in for “a” in each equation. Example:V=V0 - gtX=X0 + V0t - (1/2)gt2-2g(X-X0)=V2-V02 It is very important that you don’t forget that g needs to be
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