Atoy car's movement is measured using photogates. the car's position-time graph is show below.

which of the following statements describes the velocity of this car?

a. the velocity increases, the decreases.
b. it has a constant velocity.
c. it has zero velocity.
d. the velocity decreases, then increases.

Option D

We know that speed is defined as the derivative of the position with respect to time. The derivative shows the slope changes that occur in the graph of the function shown.

Observe the attached image.

Notice that at the beginning the graph resembles a line whose slope is constant. This means that during this time interval (t1) the speed is approximately constant and greater than zero. Then we observe a time interval during which the function is approximately horizontal, parallel to the time axis. In this interval (t2) the slope is approximately 0. This means that in this interval the velocity is approximately 0. Finally, the graph has a positive and large slope. This means that during the last time interval (t3) the speed increases. Therefore the correct option is D.

D. The velocity decreases, then increases.

v=ir = 3x15 =45 v

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