# ch02 - CHAPTER 2 KINEMATICS IN ONE DIMENSION ANSWERS TO...

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CHAPTER 2 KINEMATICS IN ONE DIMENSION ANSWERS TO FOCUS ON CONCEPTS QUESTIONS 1. (b) Displacement, being a vector, conveys information about magnitude and direction. Distance conveys no information about direction and, hence, is not a vector. 2. (c) Since each runner starts at the same place and ends at the same place, the three displacement vectors are equal. 3. (c) The average speed is the distance of 16.0 km divided by the elapsed time of 2.0 h. The average velocity is the displacement of 0 km divided by the elapsed time. The displacement is 0 km, because the jogger begins and ends at the same place. 4. (a) Since the bicycle covers the same number of meters per second everywhere on the track, its speed is constant. 5. (e) The average velocity is the displacement (2.0 km due north) divided by the elapsed time (0.50 h), and the direction of the velocity is the same as the direction of the displacement. 6. (c) The average acceleration is the change in velocity (final velocity minus initial velocity) divided by the elapsed time. The change in velocity has a magnitude of 15.0 km/h. Since the change in velocity points due east, the direction of the average acceleration is also due east. 7. (d) This is always the situation when an object at rest begins to move. 8. (b) If neither the magnitude nor the direction of the velocity changes, then the velocity is constant, and the change in velocity is zero. Since the average acceleration is the change in velocity divided by the elapsed time, the average acceleration is also zero. 9. (a) The runners are always moving after the race starts and, therefore, have a non-zero average speed. The average velocity is the displacement divided by the elapsed time, and the displacement is zero, since the race starts and finishes at the same place. The average acceleration is the change in the velocity divided by the elapsed time, and the velocity changes, since the contestants start at rest and finish while running. 10. (c) The equations of kinematics can be used only when the acceleration remains constant and cannot be used when it changes from moment to moment. 11. (a) Velocity, not speed, appears as one of the variables in the equations of kinematics. Velocity is a vector. The magnitude of the instantaneous velocity is the speed.

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43 KINEMATICS IN ONE DIMENSION 12. (b) According to one of the equation of kinematics ( 29 2 2 0 0 2 , with 0 m/s v v ax v = + = , the displacement is proportional to the square of the velocity. 13. (d) According to one of the equation of kinematics ( 29 2 1 0 0 2 , with 0 m/s x v t at v = + = , the displacement is proportional to the acceleration. 14. (b) For a single object each equation of kinematics contains four variables, one of which is the unknown variable. 15. (e) An equation of kinematics ( 29 0 v v at = + gives the answer directly, since the initial velocity, the final velocity, and the time are known.
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## This note was uploaded on 03/30/2012 for the course PHYSICS 201 taught by Professor Rollino during the Fall '11 term at Rutgers.

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ch02 - CHAPTER 2 KINEMATICS IN ONE DIMENSION ANSWERS TO...

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