Motion of a charged particle in electric and magnetic fields?

Question

A magnetic field has a magnitude of 1.2 10e-3 T, and an electric field has a magnitude of 5.7 10e3 N/C. Both fields point in the same direction. A positive 1.8 µC charge moves at a speed of 2.9 10e6 m/s in a direction that is perpendicular to both fields. Determine the magnitude of the net force that acts on the charge.

Now, wouldn't I add the force of the magnetic and electric fields together to get the answer? I came up with .0183 but my homework site is telling me I'm wrong.

Answer 1

The force due to the electric fld is in the direction of the fld, whereas that due to the magnetic fld is perpendicular to both the magnetic fld and the velocity of the charge. So the two forces are perpendicular and you have to calculate the resultant as sqrt (F1^2+F2^2)

Answer 2

Since the particle in question is moving at 90-degrees to both fields then it is as if it is moving directly against those fields. A peculiar arraignment since if it moved at any other angle it would have part of its movement in the direction of the two fields. The charged particle is not fired directly against the direction of the two fields because then it would be constantly decelerating. However, by moving at a direct 90-degree angle to the two fields then you can ignore the short transit distance and take the particle as if it is going directly against the other two forces.

Convert you units and subtract. The electrical and magnetic field work in the same direction and the particle works in the absolute opposite direction across the field's cross section. Add both fields and subtract the energy from the particle and that will give you a value good for almost any point along the cross section of the two fields. The assumption is made that since the particle is moving quickly and the charges of the opposing fields are strong then effects like a reduction in speed across the field's cross section, gravity, and other particle resistance can be ignored. Normally these kinds of experiments are assumed to be conducted in an absolute vacuum (which is impossible, but we can get very close to it).

So add the two fields energy and subtract the particle’s energy. The hard part is the unit conversion. According to the Einstein’s general theory electric and magnetic forces are expressions of the same force so they would combine as one force. The charged particle would be the other force working against the combined force. With vector analysis you could calculate the force at each point in the cross section of the fields, but this isn’t usually done because the cross section is so small and the particle is in it for such a short time. Like I said the hard part is getting electron volts, newtons, coulombs, and teslia to all reach a value where you can perform the simple math operations.

Answer 3

the particle is at rest so F=QVB i.e. q*0*b=0 so no force will act on it hence it will move along the x axis