00:01
All right, so we have this model rocket.
00:02
It's launched from a platform.
00:04
Initial velocity is 194 feet per second.
00:07
So the vertical motion model formula, h of t, the height in relation to time, is negative 16t squared plus v -0t plus h -0.
00:23
Okay, so v -0 is the initial velocity.
00:26
H -0 is the initial.
00:30
Velocity or h not so this is a little height so plugging our numbers in h of t equals negative 16 t squared v not the initial velocity velocity is 194 feet per second we threw it up so plus 194 times t and then our initial height is the height of the platform which is 106 feet this is our function in terms of t, height in terms of time.
01:07
Okay, now to determine the time the rocket reaches the maximum height as well as the maximum height, we need to find the vertex.
01:16
So if you're in pre -calculus or algebra 2, you do this.
01:22
You do negative b over 2a to get the x coordinate of the vertex.
01:27
That's what x is going to equal.
01:30
And then you plug it back in to find the y core.
01:33
If you're in calculus, you take the derivative and set the derivative equal to 0.
01:39
So the derivative is h prime of t equals negative 32 t plus 194, and then we would set this equal to 0.
01:55
Subtract 194, divide by 32.
01:59
That's going to come out to be 6.
02:06
Something.
02:10
So 194 divided by 32, 6 .0625.
02:15
So when you solve this, t is going to come out to be 6 .025, which is that's the time that it reaches the maximum height.
02:28
That's if you're in calculus.
02:30
If you're in algebra 2, a pre -calculus, and you haven't no derivatives yet, you do this.
02:36
So you'd get 1904.
02:38
Divided by 2 times negative 16, which is still going to give you 6 .025.
02:47
Okay? so our max time, our time, it's going to reach the maximum height at 6 .025 seconds.
02:58
Okay? to find the maximum height, you just take that 6 .025 and plug it into our function from part a.
03:12
So 6 .025 square it times it by negative 16 and then we're going to add 194 times 6 .025 and then we're going to add 106.
03:30
So 694 .04 feet is the maximum height that we get...