00:01
So we have an alpha particle traveling with an initial velocity given in these coordinates, cartesian coordinates.
00:07
And we have a magnetic field also given in the same coordinates, and it only has really a negative z component.
00:14
So the force, the lorenz force on those particles, qv cross v.
00:17
And if we look at the cross product, which i've kind of set up here, without the units anyway, we'll notice that there's no component that's going to be in the z direction of this force, because if we compute the z force, that sort of means we look at only the x and y components, and no matter which ones we pick, we're ultimately multiplying by zero, like we'll have two times zero minus zero times zero.
00:42
So the only component out of this that actually survives is the j component or the y component.
00:48
And that would be have a value of negative three, but it's times the negative j hat.
00:55
So to make this clear, the i -hat components would be, 2 times 0 minus 0 times 0.
01:02
So, of course, that's 0.
01:03
And then the y hat component or j hat components already come in with the negative sign.
01:07
And this would be 2 times negative 1 .5 in the jihad direction.
01:13
And then the z hat direction, i hope it's clear from the cross product.
01:17
That's also going to be 0...