00:01
In this example, we're going to be looking at a velocity versus time graph for an object, and we're going to be asking several questions about this object's motion.
00:13
The graph that we're working with is the following, where we have time in seconds on the x -axis.
00:21
So we'll say time, time in seconds.
00:25
And then on the y -axis, we have velocity in meters per second.
00:32
Okay, so this goes from negative 10 to positive 10.
00:37
Then we start at time t equals zero.
00:42
The first question is we want to know the object's acceleration from t equals zero to three seconds.
00:50
Okay, so from zero to three seconds, we see that we're moving at constant velocity.
00:55
So acceleration equals zero.
00:59
Next, we want to find the acceleration from t equals three to eight seconds.
01:07
Okay, so that's going to be this segment here, three to eight seconds.
01:11
So we know that's just going to be the slope of the velocity curve.
01:16
Okay, so we go from negative nine meters per second to 11 meters per second.
01:24
Okay, so we go positive 20.
01:26
20 divided by we go from 3 seconds to 8 seconds, 5 seconds.
01:32
So the acceleration is 4 meters per second squared.
01:39
Next we want acceleration between 13 and 18 seconds.
01:47
So a4t equals 13 through 18 seconds.
01:55
So that's that segment from 13 to 18 seconds where we stop.
02:02
Again, the acceleration is going to be the slope of that line.
02:05
So we go from 11 to 0 meters per second in a time of five seconds.
02:14
So that's going to be 11, negative 11, over 5 equals 2 .2 meters per second squared.
02:24
And that's negative.
02:27
Next we want to find the times at which the object has the lowest speed.
02:34
Okay, so times where v equals zero...