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 figure below. When the car changes speed it does so uniformly. Select the appropriate choice for each statement.

The answer can be less than, equal to, greater than, true or false.

the speed is...zero at 29 sec.

the speed at 46 sec is....the speed at 76 sec.

the x-acceleration is...zero at 26 sec.

at 46 sec, the speed is as high as it gets.

the acceleration magnitude at 37 seconds is...the acceleration magnitude at 15 sec.

the x-acceleration is...zero at 37 sec

Explanation / Answer

From the givem question,

1. the speed is...zero at 29 sec.

Ans: True

As the distance time graph is horizontal, the speed of car is zero.

2.the speed at 46 sec is greater than the speed at 76 sec.

As the slope of distance time graph is greater at 46 sec than 76 sec, the speed at 46 sec is greater than 76 sec.

3.the x-acceleration is...zero at 26 sec.

Ans: True

As the car is at rest at 29 sec, the acceleration is zero at 29 sec.

4.at 46 sec, the speed is as high as it gets.

Ans: True

The slope is greatest between 40 and 60 sec, hence speed is highest at 46 sec.

5.the acceleration magnitude at 37 seconds is greater than the acceleration magnitude at 15 sec.

The curve is concave downwards at 15 sec and the curve is concave upwards at 37 sec.

hence acceleration at 37 sec is greater than acceleration at 15 sec.

6. the x-acceleration is greater than zero at 37 sec

Since the slope is increasing at 37 sec, the acceleration is positive at 37 sec.

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