00:01
This problem shows two waves.
00:05
I don't think it's completely clear exactly what those two waves are, and i am going to show you what i'm confident they are, but if you really think about it, it doesn't really tell us exactly which wave is which.
00:33
So let's say that these are the two waves.
00:46
The one wave that i'm going to make red goes from two to five.
00:55
And by the way, this goes all the way out to 18.
00:58
One, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, sixteen, seventeen, eighteen, eighteen, okay, the first wave goes from two out to five, three, four, five, and then also to six, upwards, and then downwards.
01:27
All right, the second wave goes from 13, one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, downwards.
01:50
Whoops downwards over.
01:54
Whoops, made that too tall.
02:02
Up over 17.
02:07
Okay, i'm going to believe that these are the two waves that they're talking about.
02:14
This one moves at one meter per second, and the other one also moves at one meter per second.
02:20
However, we're doing two second intervals.
02:23
So this is t equals zero.
02:26
So let's go ahead and draw t equals two.
02:42
T equals two when they're moving one meters per second is going two times one is two.
02:53
So it's going to be two spaces over each time, two meters.
03:01
So let's draw this.
03:03
One, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, sixteen, seventeen, eighteen, eighteen, sixteen, eighteen.
03:11
The red one's going to move over two meters.
03:14
It used to extend from two to five.
03:18
That bottom part used to extend from two to five.
03:22
Now it's gone over two, so it's going to go from four to seven.
03:28
Five plus two is seven.
03:30
One, two, three, four, five, six, seven.
03:36
And then it'll go up like that.
03:41
All right.
03:43
This green one.
03:44
Used to start at 15.
03:48
If we take two off of that, it'll be 13.
03:56
Did it start at 15? where am i getting my 15 from? yeah, i don't know where i got my 15 from.
04:05
He used to start at 12.
04:08
No, at 13.
04:11
This is 13 right here.
04:14
It used to start at 13.
04:16
Now it's going to start at 11.
04:19
So, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11.
04:26
Downward, upward, over three, and back down.
04:33
All right, so they haven't even reached each other yet.
04:37
So let's try.
04:38
T equals four.
04:53
One, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, thirteen, thirteen, sixteen, seventeen, eighteen, eighteen.
05:02
Okay.
05:03
The red one used to be at one, two, three, four.
05:05
So now it's going to be at six.
05:06
One, two, three, four, five, six.
05:10
It's going to go over three, and then it's going to go up for one.
05:21
The green one used to be at one, two, three, four, five, six, seven, eight, nine, ten, eleven.
05:30
It used to be eleven.
05:31
Eleven, minus two, nine.
05:33
One, two, three, four, five, six, seven, eight, nine.
05:37
Uh -oh.
05:38
So one, two, three, four, five, six, seven, eight, nine...