00:01
So we have six particles.
00:04
We're supposed to express their angular momentum according to the center is at the location of particle five.
00:15
All right.
00:16
Now, all of the angular momentum are either going to be in the plus z or minus z directions because it's got to be perpendicular to the plane containing our radius vector and our velocity vector.
00:34
So we want to calculate the angular momentum of each particle relative to number five.
00:43
So l1, you take the velocity is moving to the right, that's in the positive x direction.
00:55
You take the perpendicular direction to that.
00:59
So it's h times v.
01:03
And then the direction of that we get from the right -hand rule, which points outward, which is the plus z direction.
01:21
So i'll give that is k.
01:31
L2, that one's zero because the radius vector, which is h, points along the direction of v so that the cross product gives zero.
01:54
And then l3, so l3, the velocity is going the opposite direction.
01:59
We still have the same h, and so we're going to get actually.
02:03
Actually minus hv times k because there's really no difference here except the sign of the velocity compared to number one.
02:21
And then number four.
02:24
So now the distance from five to four, that's d times v...