00:01
So for this problem, we are given the components of the magnetic field.
00:05
And we know that this particle is moving with speed v in the negative y direction.
00:16
So we can write the velocity vector as negative v times j.
00:28
So for calculating the lorentz force, we can directly apply its definition, which is qv cross b.
00:37
And then we can simply calculate the determinant of this 3x3 -matrix to find out its components.
01:13
So it turns out that f equals negative qvbz times i plus qvbx.
01:37
So for part b, if q is greater than 0, what must the size? of the components of b, if the components of f are all non -negative.
02:02
So we know that fx should be greater than or equal to zero, and fz should be greater than or equal to zero, and f y is already zero.
02:23
So the sign of b y doesn't matter...