00:01
Okay, so we're given the equation of motion for a charged particle in an electromagnetic field.
00:09
We're told what the components of electric and magnetic field look like.
00:13
They're constant.
00:14
We're also given our initial velocity, which is in the z direction.
00:20
So the first thing we want to do is we want to calculate.
00:25
We want to write down the equations.
00:27
Equations.
00:28
Okay, so we can figure out this cross product by taking the determinant.
00:35
Okay, so we get this equation, and let's look at the vector components of it.
01:27
So this equation here, the y equation, tells us that y dot is a constant.
01:35
That's our initial velocity in the y direction, which is zero because our initial velocity is in the z direction.
01:48
So that means we've got zero velocity in the y direction all along.
01:58
So that means that the motion is in the xz plane.
02:10
Okay, so let's take this equation, and i can integrate it because we just got time derivatives here.
02:18
So we get m times z dot equals qbx plus some constant, let's call it c1.
02:32
So we'll get more constants as we integrate these things.
02:37
Okay, so that tells me what z dot is, and i can substitute that back into this equation.
03:04
And then it's z dot, which is, okay, okay, now i'll bring the x terms over to the left.
03:36
And first of all, i'll divide by m.
03:38
So i get whatever c1 might be.
04:12
So the way this goes is we solve this equation for x.
04:19
And then once we got the answer, we plug it back up in here.
04:23
And we integrate this equation and find z.
04:28
So let's look now at part a.
04:34
So now we're going to say what if v zero is e over b.
04:43
So if v zero is e over b, then it's easy to see that our force, that's equal to zero...