Video Transcript
Which two lines correspond to the
two objects that have the greatest difference in speed?
Here, we’ve been given a speed–time
graph with five lines on it. Each line represents the motion of
a different object, and we want to find which two objects have the greatest
difference in speed. Now, the greatest difference in
speed must be between the fastest moving object and the slowest moving object. So we need to pick out the object
with the greatest speed and the object with the lowest speed.
Let’s start by taking a better look
at the speed–time graph. First notice that the vertical axis
shows the speed at which the objects are traveling. And the horizontal axis shows the
time that the objects have been traveling for. Also, 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, speed or time,
increases. So as we look higher up along the
vertical axis, we see greater and greater values of speed. Likewise, as we look farther to the
right along the horizontal axis, we see greater and greater values of time. We should also notice that all of
the lines shown on the graph, A, B, C, D, and E, are horizontal.
On a speed–time graph, a horizontal
line corresponds to an object whose value of speed does not change as time goes
on. Therefore, we know that all five of
the objects are traveling at constant speeds, but this does not mean that they’re
all moving at the same speed. In fact, we know they’re all
traveling at different speeds because each line corresponds to a different value on
the vertical or speed axis.
Now, we want to know which two
objects have the greatest difference in speed. So we need to pick out the object
with the greatest speed and the object with the lowest speed. To do this, we simply need to look
at the position of each line on the vertical axis. The highest line will correspond to
the greatest speed, and the lowest line will correspond to the lowest speed.
Knowing this, we can see that the
object with the greatest speed is represented by line A because this line is the
highest up on the vertical axis. We can also see that the object
with the lowest speed is represented by line E because, out of all the lines, line E
is the lowest on the vertical axis.
These two lines have the greatest
difference in speed, and we can see this difference represented by the space between
the lines along the vertical axis. Therefore, the lines corresponding
to the two objects with the greatest difference in speed are line A and Line E.
