Need Help with this questions bcuz i m poor in physics (1 Viewer)

[lazyandcool]

Dear Physicists

i have a problem with this question

The electric deflecting plates in a cathode ray tube are 15mm apart and have a potential difference of 1200 V across them.A beam of charged particles moving at 2 X 10^4 m/s travel through the plates undeflected.Calculate
a) the electric field between the plates
b)the strength of magnetic field which causes the beam to travel straight through the electric plates
c) In a separate experiment using the same cathode ray tube the beam again travels through the plates undeflected but this time the gravitational force on particles in the beam opposes the electric field.Calculate the mass of each particle


any suggestions would be greatly appreciated

 

[msum1uknow]

use F=qvBsin where angle equals 1
and e=v/d