Question

A proton moves through a region of space where there is a magnetic field B = (0.45i + 0 38j) T and an electric field E = ( 3.0 i – 4.2 j ) x 10^3 V/m. At a given instant, the proton’s velocity is V = ( 6.0 i + 3.0 j - 5.0 K ) x10^3 m/s . Determine the components of the total force on the proton.

Answer 1

At first you have to determine which force influences on the proton. Accorfdng to the task, both electric force and a magnetic force.
So, the following formulae to use : F = Eq 
Fmagnetic=q(v×B). Using these you can calculate vector cross product B (B = (0.45i + 0 38j),  that is hiding in  i and j directions which will interact with k.
Hope it has become clear so that you can solve this task! Regards!