00:02
So we take the ball and throw it up at 20 meters per second.
00:06
And we want to know when it says apex, so when it stops moving.
00:11
So basically, we know that, let's see, i guess the best equation to use would be the v2 is the v1 plus acceleration times delta t.
00:33
And this is set up so that we want this second velocity.
00:38
In this form, but we really don't.
00:40
What we're after right now is delta t.
00:44
So we're going to switch this up.
00:45
We're going to say delta v, which is just a change in velocity, and that is equal to a delta t.
00:58
So really all we did is move the v1 over the other side there.
01:03
And then delta t, we have, so delta v over a is delta t, and that's just dividing both sides by a.
01:15
So now, if the change in velocity has to be 20 meters per second, right? we have to be careful about positives and negatives here...