A car travels a certain distance along a straight road (in the +x direction). Th

Question

A car travels a certain distance along a straight road (in the +x direction). The distance the car travels as a function of time is shown in the fiqure below. When the car changes speed it does so uniformly. Select the appropriate choice for each statement. 1000 E 800 600 400 200 20 40 60 80 Time (s) The speed is. zero at 29 sec The x-acceleration is zero at 67 sec At 70 sec, the speed is as high as it gets. The acceleration magnitude at 15 sec is.... the acceleration magnitude at 36 sec The speed at 4 sec is.... the speed at 70 sec The x-acceleration is zero at 15 sec Submit Answer Tries 0/12 usina the araph above, calculate the average speed of the car for the period from 0 to 80,.0 5 Submit Answer Tries 0/12

Explanation / Answer

Speed is the slope of d vs t curve.

at 29 sec , speed = slope = 0

Ans: Equal to  

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at 67s, curve is straight line hence speed is constant.

so acceleration will be zero.

Ans: equal to

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at 70 sec, slope does have greatest value.

True

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acc at 15 sec is less than than at 36 sec.

(because change is lesser at 15 sec.

lesser slope to zero.)

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at 70 sec, slope is greateest.

Less than

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at 15sec, speed changes so acceleration is not equal to zero.

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average speed = distance / time

v = 1200 / 80 = 15 m/s

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