Video Transcript
Which two lines correspond to the
two objects that have the least difference in speed?
In this question, we’ve been given
a speed–time graph with lines representing the motion of five different objects. We want to find the two objects
that have the least difference in speed. So let’s start by taking a closer
look at the graph. We can see that the vertical axis
shows the speed at which the objects are traveling and the horizontal axis shows the
time that the objects are traveling for. Also notice that if we look at the
very ends of the axes, we can see arrowheads. Each of these indicate the
direction in which the value that’s represented by the axis, either speed or time,
increases. So as we look higher up along the
vertical axis, we see greater and greater values of speed. And as we look farther to the right
along the horizontal axis, we see greater and greater values of time.
We should also note that all of the
lines shown on the graph, A, B, C, D, and E, are horizontal. Recall that on a speed–time graph,
a horizontal line corresponds to an object whose value of speed does not change as
time goes on. And therefore, we know that all
five of the objects are traveling at constant speeds. Knowing this, we can answer this
question by mainly focusing on just the vertical or speed axis.
Notice that we can see the
difference between the speeds represented by any two lines on the graph by looking
at the space between them along the vertical axis. So another way to think about this
question is, which two lines are closest together on the vertical axis? Looking at the graph, we might
notice that lines D and E are pretty close together, but they’re not the closest
pair of lines. Actually the two lines that are the
closest together are line A and line B up here at the top. They have the least amount of space
between them on the vertical axis. Therefore, the lines corresponding
to the two objects with the least difference in speed are line A and line B.
