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Question Video: Comparing the Greatest Average Speeds of Two Objects Science

The positions of two objects are shown at one-second time intervals, starting at a time of zero seconds. Between two seconds and three seconds, which object has the greater average speed?

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Video Transcript

The positions of two objects are shown at one-second time intervals, starting at a time of zero seconds. Between two seconds and three seconds, which object has the greater average speed?

Another way that we can think about this diagram showing the objects’ motion is to imagine that the objects are leaving marks on the ground at regular intervals. So, we can reimagine the diagram to look like this. We represent objects A and B as dots, and that avoids confusion about their relative positions. Then labeling each dot so that it represents when that mark was made, we can begin to understand the objects’ relative speeds.

Remember, speed is the measurement of the distance that an object moves over some quantity of time. Here we see that object A moves the same amount of distance in each time interval. Therefore, we can say that object A moves with a uniform or constant speed. Each snapshot taken one second apart is an equal distance apart. So, the object never moves more or less distance than in the previous second. Object B, on the other hand, always covers a different distance between intervals. Object B starts out slow, covering very little distance in one second, but it ends up moving very fast, covering lots of distance in one second.

To know when the objects are moving at the same speed since the time intervals are always the same, we need to look at how much distance they move between intervals and compare. Look at this diagram, annotated with the objects’ relative speed. Between zero and one second, object A moved more distance than object B. So, we can say it moved faster. Between one to two seconds, B moved more distance than A. So, we can say it moved faster. And between two to three seconds, A and B moved by the same amount. This must mean then that they moved at the same speed between two and three seconds. So, the correct answer here is that the average speeds are the same between two seconds and three seconds.

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