rand prob 41

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course phy121

sept 20, 4:35pm

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?vAve= ‘ds/’dt

vAve= (115m-75m)/(11s-4s)

vAve= 40m/7s

vAve= 5.7m/s

aAve= ‘dv/’dt

aAve= (20.5m/s-10m/s)/(11s-4s)

aAve= 10.5m/s / 7s

aAve= 1.5m/s^2

This means that the average acceleration is 1.5m/s every second.

If acceleration was uniform, then If we plotted a v vs t graph, the line would be straight. The average velocity would be at the midpoint of the interval (at 7.5s), and would be equal to the average of initial and final velocities. Therefore, acceleration is not uniform.

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Excellent.

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