00:01
Okay, we have a position function, and this is a rocket being shot up, and then it's going to splash down in the ocean.
00:12
Okay, so here's our rocket.
00:15
It's starting at 234 feet.
00:18
It's going to go up, and then it's going to come down.
00:21
And our first question is, when is splash down? okay, so splash down is going to occur, right? because this is time and this is height.
00:32
So splashdown is going to occur when the height is zero.
00:36
So we're just going to set this function equal to zero and solve it.
00:47
This is quadratic, so i'm going to use the quadratic formula, opposite of b, plus or minus b squared minus 4a, c, the whole thing over 2a.
01:09
Let's run that, put it in our calculators.
01:15
Okay, we are gonna get two values, negative 2.
01:19
Do they tell us how many decimal places? no.
01:25
All right, so negative 2 .56 and 18 .68 seconds.
01:33
Okay, so what's up with this negative? well, that makes sense if you think about this being the graph of a parabola.
01:42
It's got a negative leading coefficient, so that means that it's going to open downward.
01:48
We're not starting at the ground, but if we continued our graph, right, made that like a parabola that had two x intercepts, we would see that one would be on the negative side of the graph.
01:59
So that's where that's coming from...