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

1) EQUAL TO

The slope is zero means no distance being covered and hence speed is zero.

2) EQUAL TO

Since the slope of the curve x ( t ) is constant around 67 seconds, the velocity is constant and thus acceleration vanishes at that time

3) FALSE

Since we have a steeper curve at around 50s.

4) GREATER THAN

At 15 seconds, the car is decelerating with magnitude LARGER than its acceleration at 36 sec as can be seen because the curve changes more sharply (higher curvature) at 15 seconds than at 36 seconds.

5) GREATER THAN

Just by seeing the slope.

6) LESS THAN

At 15 seconds, the position has a decreasing slope, which means the velocity is decreasing, corresponding to a negative acceleration.

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