1
00:00:03,530 --> 00:00:05,600
So the last question
we can ask us

2
00:00:05,600 --> 00:00:11,770
is what it was that v0 here
initially off the sled,

3
00:00:11,770 --> 00:00:14,680
making use of the fact
that the sled comes

4
00:00:14,680 --> 00:00:19,870
to a stop at the time that
the fuel is all used up.

5
00:00:19,870 --> 00:00:24,970
That means that our final
velocity over here is 0.

6
00:00:24,970 --> 00:00:29,840
We'll bring v0 to
the other side,

7
00:00:29,840 --> 00:00:33,960
and then we get to minus u l n.

8
00:00:33,960 --> 00:00:36,410
And the rocket
mass, by then it's

9
00:00:36,410 --> 00:00:41,520
just the dry mass-- n0 over 2n0.

10
00:00:44,380 --> 00:00:46,720
And that, of course,
cancels out here.

11
00:00:46,720 --> 00:00:53,690
And we can say that
is plus u l n of 2.

12
00:00:53,690 --> 00:00:58,640
So that was the velocity
that the sled was going with.