00:01
Okay, so we've got a high -speed passenger train traveling at 161 kilometers per hour.
00:09
So v -sub -t, 161 kilometers per hour.
00:19
But i need to multiply by a thousand meters in a kilometer and divide by 3 ,6001 kilometers per hour.
00:34
Seconds in an hour.
00:37
So let me just go ahead and do that.
00:43
And that's going to give me meters per second.
00:46
So v sub t equals 161 times 161 times a thousand divided by 3 ,600.
01:05
Okay, so that's 45, 44 .7 meters per second.
01:13
Okay, it rounds a bend.
01:32
So then we've got, i guess, another train.
01:38
D equals 676 meters ahead.
01:45
And that one is moving v sub d.
01:56
Now, i guess l for locomotive, 29 kilometers per hour.
02:07
So again, i want to put that in and convert it to meters per second.
02:16
So v.
02:19
V sub l, i'm just going to use a lowercase l, is 29 times a mistake is last time.
02:35
29 times 1 ,000 divided by 3 ,600.
02:39
Okay, so that's 8 approximately meters per second.
02:44
Put d in here also.
02:50
Okay.
02:51
And then here i wrote lowercase l because it's easier.
02:56
Okay.
02:59
Now there's a figure 2 -32 that's going to help me understand this.
03:09
So it shows the high -speed train coming around a curve, but then it's going to move straight.
03:17
So let's say that this is the high -speed train.
03:22
And it is going this direction and then there's a distance d and then here's the locomotive also going in that direction.
03:46
Okay.
03:48
Now, a.
04:02
So we want to avoid collision.
04:05
So for the locomotive, and i'm going to say that x is here, x is going to be x initial, which is zero, plus vx initial t, that would be vt t, minus one -half a t squared.
04:42
And we want to see, i believe, where this x equals x for the other train.
04:52
The other train is going x initial is d plus vlt.
05:05
So i could solve this for t or a.
05:21
Let's think about this.
05:30
So i'm going to try to solve it for t.
05:35
That's going to give me d.
05:40
Just rearranging plus vl minus vtt now i think i want to go the other direction so i'm going to write negative d plus vt minus vlt um minus one half a t squared equals zero okay now i want to to write it in the other.
06:46
Yeah, i'm going to write it.
06:50
Actually, i'm going to add everything to the other side.
06:52
So now it's going to be one -half a t squared plus vl minus vt, t plus d equals zero.
07:13
So just adding everything to the other side.
07:17
So t is going to equal negative vl minus vf.
07:28
This is the quadratic formula now, plus or minus the square root of vl minus vf squared, minus 4 times a times c.
08:01
Well, 4 times 1 half, it's 2.
08:04
So i'm going to put a 2 in there now.
08:10
A, d over 2a, which in this case is just a.
08:32
Okay.
08:34
Now, i don't want to worry about the plus or minus, because when it just hits is going to be when this term, this whole term back here, is zero.
08:54
So now t equals vf minus vl over a.
09:17
Wait a minute...