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Unformatted text preview: Physics 7B Practice Quiz 9
DL Section Number ____________ Name (last, first) ____________________________ First two letters of last name: Student ID _______________________ I certify by my signature that I will abide by the code of academic conduct of the University of California. Signature No books or notes. Calculators OK. Show all your work below. Answers alone do not receive credit! 1. A car is moving forward at a certain speed and the driver applies the brakes. The car comes to rest decelerating at a constant rate. a) (1.5 pts) Which of the graphs below best depicts the speed v of the car as a function of time t ? Circle the correct graph and provide one sentence and/or equation justifying your choice. b) (1.5 pts) Which of the graphs below best depicts the position x of the car as a function of time t ? Circle the correct graph and provide one sentence and/or equation justifying your choice. 2. (1.5 pts) If the car in problem 1 is initially going 30 km/h an comes to rest after 10 seconds, what is its acceleration? constant acceleration, 1D: x(t) = x0 + v0t + ½ at2 v(t) = v0 + at a = dv/dt 1 a) 1 b) 2 P 1.5 Selected the correct graph of the line with nega9ve slope and gave the equa9on v(t)=v0 + at OR an explana9on that involved a constant nega9ve accelera9on Selected the wrong graph but used the equa9on v(t)=v0 + at or had an explana9on that said the velocity should reﬂect a constant accelera9on P Selected the correct graph of the parabola that asymptotes at some posi9ve value of x and gave the equa9on x(t) = x0 + v0t + 1/2 a t^2 OR an explana9on that involved a constant nega9ve accelera9on and the fact that the 1.5 car comes to rest Selected the wrong graph but gave the equa9on x(t) = x0 + v0t + 1/2 a t^2 OR an explana9on that involved a constant nega9ve accelera9on and the fact that the car comes to rest Used v(t)=v0 + at or delta(v)/ delta(t) = a to solve for a=
.83 P 1.5 meters per second squared Q 1.2 Q 1.2 Used v(t)=v0 + at or delta(v)/ delta(t) = a to solve for accelera9on but made a Q 1.2 minor algebra error Used v(t)=v0 + at or delta(v)/ delta(t) = a to solve for accelera9on but made a minor algebra error and had R 0.9 the wrong units R Selected the correct graph of the line with nega9ve slope but gave the wrong formula or 0.9 explana9on R Selected the correct graph of the parabola that asymptotes at some posi9ve value of x but gave the 0.9 wrong formula or explana9on Selected the wrong graph but men9oned that the second deriva9ve of posi9on is accelera9on S 0.6 Selected the wrong graph but men9oned that the deriva9ve of velocity is accelera9on S 0.6 Did not use the correct formula, but the formula did S 0.6 have accelera9on in it T Selected the wrong graph but knew the correct end points for 0.3 the velocity T Selected the wrong graph but men9oned the car would come to 0.3 a stop T 0.3 N/A U 0 Selected the wrong graph and did not oﬀer any explana9on U 0 Selected the wrong graph and did not oﬀer any explana9on U 0 Didn't answer the ques9on or use any equa9ons constant acceleration, 1D: x(t) = x0 + v0t + ½ at2 v(t) = v0 + at a = dv/dt ...
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 Fall '08
 PARDINI
 Physics

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