Exam1-solutions - Version 103 Exam1 distler (56295) 1 This...

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Unformatted text preview: Version 103 Exam1 distler (56295) 1 This print-out should have 13 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A particle moving at a velocity of 8 m / s in the positive x direction is given an acceleration of 5 . 2 m / s 2 in the positive y direction for 7 s. What is the final speed of the particle? 1. 4.38634 2. 6.86804 3. 2.0004 4. 57.9956 5. 18.1005 6. 13.1495 7. 21.3965 8. 5.88673 9. 37.2688 10. 4.78357 Correct answer: 37 . 2688 m / s. Explanation: Let : v xf = v xi = 8 m / s . a y = 5 . 2 m / s 2 , and t = 7 s . The vertical velocity undergoes constant ac- celeration: v yf = v yi + at = 0 + (5 . 2 m / s 2 )(7 s) = 36 . 4 m / s . Thus v f = radicalBig v 2 xf + v 2 yf = radicalBig (8 m / s) 2 + (36 . 4 m / s) 2 = 37 . 2688 m / s . 002 10.0 points A driver in a car traveling at a speed of 62 . 4 mi / h sees a deer 94 m away on the road. Calculate the magnitude of the acceleration necessary for the car to stop just barely miss- ing the deer (assuming that the deer does not move in the meantime). 1. 2.61619 2. 4.70936 3. 3.54871 4. 3.97935 5. 3.3345 6. 2.0796 7. 4.65036 8. 2.85199 9. 4.13732 10. 3.01859 Correct answer: 4 . 13732 m / s 2 . Explanation: For constant acceleration, Let : v i = 62 . 4 mi / h , x = 94 m , and v f = 0 . v 2 f = v 2 i + 2 ax = 0 a = v 2 i 2 x = (62 . 4 mi / h) 2 2 (94 m) = 4 . 13732 m / s 2 . 003 10.0 points The diagram describes the acceleration vs time behavior for a car moving in the x- direction. b b a P Q t At the point Q , the car is moving 1. with a constant speed. 2. with a decreasing speed. Version 103 Exam1 distler (56295) 2 3. with an increasing speed. correct Explanation: a = dv dt . As long as the acceleration is positive the velocity is always increasing. 004 10.0 points The position-versus-time graph below de- scribes the motion of three different bodies (labeled 1, 2, 3). 1 2 3 x B x A t A t B x t A B Consider the average velocities of the three bodies. Which of the following statements is correct? 1. v 1 = v 2 = v 3 correct 2. v 1 > v 2 and v 3 > v 2 3. v 1 < v 2 < v 3 4. v 1 > v 2 > v 3 Explanation: Average velocity is v = displacement time = x B x A t B t A ....
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This note was uploaded on 11/29/2011 for the course PHY 302K taught by Professor Kaplunovsky during the Spring '08 term at University of Texas at Austin.

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Exam1-solutions - Version 103 Exam1 distler (56295) 1 This...

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