00:01
We've got a free -falling object, and it takes one and a half seconds to travel the last 30 meters before it hits the ground.
00:20
What was its height above the ground? okay.
00:24
Well, its height for the last 30 meters, which i'm going to say is h2, is going to equal, um, wait a minute.
00:43
Wait a minute, its height in the end is zero.
00:47
And that's going to equal h2.
00:59
So x or y equals y initial plus v initial t, g, t squared.
01:25
Okay, we know t and we know h2.
01:33
So i can solve this for the velocity at before the one and a half seconds.
01:42
So v2 is going to equal 1⁄2 1⁄2 minus h2 over t.
02:01
So let's go ahead and get that.
02:04
T equals 1 .5.
02:06
G equals 9 .80.
02:10
H2 is 30.
02:16
V2 equals 1⁄2 gt squared minus h2 over t.
02:33
So that gives me, i guess this makes sense, it gives me a negative number, and it is going downward...