PHY2048_chapter4 - Chapter 4 Motion in Two and Three...

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Unformatted text preview: Chapter 4 Motion in Two and Three Dimensions In this chapter we will continue to study the motion of objects without the restriction we put in chapter 2 to move along a straight line. Instead we will consider motion in a plane (two dimensional motion) and motion in space (three dimensional motion). The following vectors will be defined for two- and three- dimensional motion: Displacement Average and instantaneous velocity Average and instantaneous acceleration We will consider in detail projectile motion and uniform circular motion as examples of motion in two dimensions Finally we will consider relative motion, i.e. the transformation of velocities between two reference systems which move with respect to each other with constant velocity. (4 -1) Position Vector ˆ ˆ ˆ r xi yj zk = + + r ( 29 ˆ ˆ ˆ 3 2 5 r i j k m = - + + r (4 -2) P The position vector r of a particle is defined as a vector whose tail is at a reference point (usually at the origin O) and its tip is at the particle at point P. t 2 t 1 Displacement Vector 1 2 For a particle that changes postion vector from to we define the displacement vector as follows: r r r ∆ r r r 2 1 r r r ∆ =- r r r 1 2 The position vectors and are written in terms of components as: r r r r 1 1 1 1 ˆ ˆ ˆ r x i y j z k = + + r 2 2 2 2 ˆ ˆ ˆ r x i y j z k = + + r ( 29 ( 29 ( 29 2 1 2 1 2 1 ˆ ˆ ˆ ˆ ˆ ˆ r x x i y y j z z k xi yj zk ∆ =- +- +- = ∆ + ∆ + ∆ r (4 -3) 2 1 x x x ∆ =- 2 1 y y y ∆ =- 2 1 z z z ∆ =- The displacement r can then be written as: ∆ r t t + Δt Average and Instantaneous Velocity Following the same approach as in chapter 2 we define the average velocity as: displacement average velocity = time interval ˆ ˆ ˆ ˆ ˆ ˆ avg r xi yj zk xi yj zk v t t t t t ∆ ∆ + ∆ + ∆ ∆ ∆ ∆ = = = + + ∆ ∆ ∆ ∆ ∆ r r The (instantaneous) velocity is the limit: lim r dr v t dt t ∆ = = ∆ ∆ → r r r (4 - 4) Average and Instantaneous Acceleration...
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This note was uploaded on 02/12/2010 for the course BCN 1210 taught by Professor Fobair during the Spring '09 term at University of Florida.

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PHY2048_chapter4 - Chapter 4 Motion in Two and Three...

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