00:01
The question says that a man is running and steadily increases his speed for three minutes, walks for five minutes, stops for two minutes, runs for five minutes, and then walks for four.
00:11
We're asked to graph his distance s versus time t, and also to graph d s over dt, or the derivative.
00:20
So we can start by graphing his initial run.
00:26
So he steadily increased his speed over time for three minutes, and that means he accelerated.
00:32
And that's going to give us a positive curve like that as he increases the amount of distance he covers over time.
00:41
And so that's different from when he walks for the next five minutes.
00:45
He walks at a consistent speed.
00:48
He does not increase his speed for five minutes.
00:51
So we're going to have a positive, steady increase here for the next five minutes.
01:02
And then he stops for two minutes.
01:04
So he covers no distance in this time.
01:09
So we have a horizontal line for two minutes.
01:16
And then he runs for five minutes.
01:17
So again, he has a positive straight line here that is a higher slope than when he walked, because he is covering more distance over time than when he walked.
01:32
And then he walks for the next four minutes...