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course Phys201
6/13@7:00 pm
An automobile traveling a straight line is at point A at clock time t = 4 sec, where it is traveling at 10 m/s, to point B at clock time t = 11 sec, where it is traveling at 20.5 m/s. Point A is 75 meters from the starting point and point B is 115 meters from the starting point. What are the average velocity and the average acceleration of the automobile during the specified time? What evidence is there that the acceleration is or is not uniform?
The acceleration is uniform because the problem states that the automobile is going in a straight line.
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The automobile is traveling in a straight line. That doesn't mean its v vs. t graph is a straight line.
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Pt A= 4 sec, 10 m/s, 75 m from start
Pt B=11 sec, 20.5 m/s, 115 m from start
Avg velocity=`ds/`dt 115 m-75m/11sec-4 sec=40m/7sec=6 m/s
Avg acceleration=`dv/`dt 20.5m/s-10 m/s/11sec-4sec=10.5m/s/7sec=2 meters/sec/sec
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If acceleration is uniform the v vs. t graph is a straight line, in which case the average velocity occurs at the midpoint of the interval and is equal to the average of the initial and final velocities.
Is this the case here?
What is your conclusion about the uniformity of the acceleration?
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