s09_exam1_rubric

s09_exam1_rubric - Ques%on 2 P1 = 2 m t s P2 = 50 − 3...

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Unformatted text preview: Ques%on 2 P1 = 2 m t s P2 = 50 − 3 P1 = P2 m t s m m t = 50 − 3 t s s t = 10 s P1 = 20 m 2 Rubric: * Draws an appropriate picture or somehow indicates they read the problem +1 * Somewhere use a posi%on versus %me equa%on appropriate for constant velocity: +2 * Recognize that they are at the same place when their posi%ons are the same: +3 • Setup the correct equa%on for each person: +3 •  get the correct posi%on: +1 Ques%on 4 ˆ ˆ D1 = 3m(cos( 30 )i + sin( 30 ) ˆ ) = 2.6i + 1.5 ˆ j j D2 = 2 mˆ j ˆ D = D + D = 2.6i + 3.5 ˆ j 1 2 Rubric: * In length, angle nota%on * Correct formula for magnitude: 4 * correct number: 1 * Correct formula for direc%on: 4 * correct number: 1 • In i ­hat,j ­hat nota%on * breaks first displacement into components: 4 * knows to add to second: 2 * correct x displacement: 2 * correct y displacement: 2 Ques%on 5: m v 2 33 a= = = 4.5 2 r 2 s direction of position vector is: s vt ( 3)(1.75 ) θP = = = = 2.63 radians =150 o rr 2 direction of acceleration vector = 180 o from position vector θ a = 330 0 m ˆ a = ( 4.5 2 )(cos( 330 )i + sin( 330 ) ˆ ) j s m ˆ = ( 3.9i − 2.25 ˆ ) 2 j s Rubric: * knows magnitude of accelera%on is v^2/r: 4 points * gets right answer for magnitude: 1 point * knows theta =s/r: 2 points * knows accelera%on is 180 degrees from posi%on: 2 points * right answer: 1 point. ...
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This document was uploaded on 12/28/2011.

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