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Unformatted text preview: revfnii 01 – RUDE, DAVID – Due: Dec 15 2007, 10:00 pm 1 Question 1, chap 2, sect 2. part 1 of 1 10 points The graph below shows the velocity v as a function of time t for an object moving in a straight line. t v t Q t R t S t P Which of the following graphs shows the corresponding displacement x as a function of time t for the same time interval? 1. t x t Q t R t S t P 2. t x t Q t R t S t P 3. t x t Q t R t S t P correct 4. t x t Q t R t S t P 5. t x t Q t R t S t P 6. t x t Q t R t S t P 7. t x t Q t R t S t P 8. None of these graphs are correct. 9. t x t Q t R t S t P Explanation: The displacement is the integral of the ve- locity with respect to time: vectorx = integraldisplay vectorv dt. Because the velocity increases linearly from zero at first, then remains constant, then de- creases linearly to zero, the displacement will increase at first proportional to time squared, then increase linearly, and then increase pro- portional to negative time squared. From these facts, we can obtain the correct answer. t x t Q t R t S t P Question 2, chap 2, sect 2. part 1 of 1 10 points A train car moves along a long straight track. The graph shows the position as a function of time for this train. x t The graph shows that the train 1. slows down all the time. correct 2. moves at a constant velocity. 3. speeds up all the time. revfnii 01 – RUDE, DAVID – Due: Dec 15 2007, 10:00 pm 2 4. speeds up part of the time and slows down part of the time. Explanation: The slope of the curve diminishes as time increases, hence the train slows down all the time. Question 3, chap 2, sect 3. part 1 of 1 10 points A graph shows a particle’s position (vertical axis) vs time (horizontal axis. The slope of this curve tells you 1. not covered in the reading assignment 2. the particle’s acceleration 3. the particle’s speed 4. the particle’s instantaneous velocity cor- rect 5. the particle’s average velocity Explanation: This relates back to the concept of the derivative. The derivative gives you the slope of the tangent line to the curve at some point. So in this case the slope (Δ x/ Δ t ) is like a velocity. Since this is a slope of a tangent line (which gives slope at that instantaneous point), we say this is the ”instantaneous ve- locity” of the particle. Question 4, chap 2, sect 4. part 1 of 1 10 points The diagram describes the acceleration vs t 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 an increasing speed correct 2. with a constant speed 3. with a decreasing speed Explanation: a = dv dt . As long as the acceleration is positive the velocity is always increasing. Question 5, chap 2, sect 4. part 1 of 1 10 points Which of the following describe possible scenarios?...
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This note was uploaded on 03/02/2009 for the course PHY 58235 taught by Professor Kleinman during the Spring '09 term at University of Texas.
- Spring '09