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Unformatted text preview: Physics 411 Tips Solving problems Write the question down o Known and unknown o Find relevant equations o Do any algebra o Plug in o Box answer o 1n problem per page Get partial credit Vector Kinematics Vector: Directed as a line segment Displacement vector: direction Coordinate independence Addition of vectors o Vector A + Vector B =VA+VB Communitive property o Subtraction of vectors Addition of one vector and the negative of another vector D/N exist o Multiplication of a vector by a scalor 2A: Same direction, twice as long Scalor: No direction Called a velocity vector Magnitude = speed No such thing as time squared Change in velocity We have seen that position, velocity and acceleration are vector quantities, and we have now used them in one dimension. How do we use them in three dimensions? Let's review a little to make sure the concepts are known. We denote the position of an object by the position vector , r . The position vector is with respect to some arbitrary coordinate system that we chose to simplify the problem. We normally work with vectors in terms of their components, and the components of the position vector (in two dimensions) are r xi yj = + (3.1) A finite displacement is denoted by r 2 r 1 = r and is a vector sum. The average velocity is then v r r t t ave =-- 2 1 2 1 (3.2) If we let the displacement and the time interval become infinitesimal, then the average velocity becomes the instantaneous velocity v dx dt = (3.3) Similarly, the average acceleration is a v v t t ave =-- 2 1 2 1 (3.4) and the instantaneous acceleration a dv dt = (3.5) The instantaneous velocity and acceleration are the slopes of the position vs....
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- Spring '09