Hard Magnetic Force on a Point Charge question...?

Question

Electrons in a television's CRT are accelerated from rest by an electric field through a potential difference of 2.5kV. In contrast to an oscilloscope, where the electron beam is deflected by an electric field, the beam is deflected by a magnetic field.

What is the speed of the electrons?

The beam is deflected by a perpendicular magnetic field of magnitude 0.80T. What is the acceleration of the electrons while in the field?

What is the speed of the electrons after they travel 4.0mm through the magnetic field?

What strength electric field would give the electrons the same magnitude acceleration as in the acceleration of the electrons while in the field?

Why do we have to use an electric field in the first place to get the electrons up to speed?

Why not use the large acceleration due to a magnetic field for that purpose?

Okay, it's a textbook question and I have no idea how to solve it. I have the equations and stuff but I don't know how to do it... I'm a non-physics major taking a hard physics course... it's a core course for my major.

Answer 1

Here,
the potential difference, V = 2.5kV = 2500V
electron charge, e = 1.6 * 10^-19 C
mass of electron, m = 9.11 * 10 ^ -31 kg
velocity, v = ?

kinetic energy = potential energy
so, 1/mv^2 = eV
or, v = (2eV/m)^.5
or, v = (2 * 1.6 *10^-19 * 2500/9.11*10^-31)^.5
so,v = 2.96 * 10^7 m/s

The rest of the question is more difficult. I will check it up and try to give you an answer later.

Hope this was helpful.