A motorist drives north for 0.58 hours at 85.0 km/h and then stops for 23 hours.

Question

A motorist drives north for 0.58 hours at 85.0 km/h and then stops for 23 hours. He then continues north, traveling at 130 km/h in 2 hours. (a) What is his total displacement? (b) How long did the entire trip take? (c) What is his average velocity? ANS: (a) 309.3 km: (b) 5.08 hours: (c)60.9km/hr A graph of position versus time for a certain particle moving along the x-axis is shown below Find the average velocity in the time intervals from (a) 0 to 2 seconds, (b) 2 to 4 seconds, (c) 4 to S seconds, (d) 5 to 7 seconds, and (e) 7 to 8 seconds. Show your work for each calculation and include any negative signs. ANS: (a) 5 m/s: (b) -2.5 m/s: (c) 0: (d) -5m/s: (e) 5 m/s Find the instantaneous velocities of the tennis player of the figure above at (a) 0.5 second, (b) 3 seconds, (c) 4.5 seconds, and (d) 7.5 seconds. Include any negative signs. ANS: (a) 5 m/s: (b) -2.5 m/s: (c) 0: (d) 5 m/s Which of the following would be the correct description of a velocity versus time graph that illustrates constant acceleration? Explain your choice (a) a horizontal line, (b) a vertical line, (c) a diagonal line, (d) a curved line ANS: choice (c) - you explain why Which of the following would be the correct description of a position versus time graph that illustrates constant acceleration? Explain your choice (a) a horizontal line, (b) a vertical line, (c) a diagonal line, (d) a curved line ANS: choice (d) - you explain why

Explanation / Answer

1) displacement = (0.58 x 85) + (130 x 2)

= 309.3 km

(b) time = 0.58 + 2.5 + 2 = 5.08 hrs

(c) average velocity = displacement / time

= 60.9 km/h

2) (a) <v> = 10 / 2 =5 m/s

(b) v = (5 - 10) / 2 = - 2.5 m/s

(c) v = (5- 5) / 1 = 0

(d) v = ( - 5 - 5) / 2 = - 5 m/s

(e) v = (0 - (-5)) / (8- 7) = 5 m/s

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