Lecture 6

Lecture 6 - Today Physics 231 General University Physics...

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1 Physics 231 General University Physics Spring 2007 Lecture 6 Today ± Motions in Two Dimensions ² Projectile Motion Position and Displacement ± The position of an object is described by its position vector , r ± The displacement of the object is defined as the change in its position ± Δ r = r f - r i General Motion Ideas ± In two- or three-dimensional kinematics, everything is the same as as in one-dimensional motion except that we must now use full vector notation ± Positive and negative signs are no longer sufficient to determine the direction Displacement and Average Velocity in Motion Diagram rv t ΔΔ = GG Average Velocity ± The average velocity is the ratio of the displacement to the time interval for the displacement ² The direction of the average velocity is the direction of the displacement vector, Δ r ² Average velocity between points is independent of path taken (as is the displacement) t Δ Δ = r v
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2 Instantaneous Velocity ± The instantaneous velocity is the limit of the average velocity as Δ t approaches zero ± The magnitude of the instantaneous velocity vector is the speed, a scalar quantity. 0 lim t d td t Δ→ Δ ≡= Δ rr v Instantaneous Velocity ± The direction of the instantaneous velocity vector at any point in a particle’s path is along a line tangent to the path at that point and in the direction of motion Caution x or y Average Acceleration ± The average acceleration of a particle as it moves is defined as the change in the instantaneous velocity vector divided by the time interval during which that change occurs.
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Lecture 6 - Today Physics 231 General University Physics...

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