Derive an expression for the motion of charged particle in combined electric and magnetic field wen the forces between electric and magnetic field are equal.

Explanation

Motion in combined electric and magnetic fields
Motion of a charged particles in combined electric and magnetic field is given by
`vecF = q (vecE + vec v xx vec B) or vec F = q vec E + q ( vec v xx vec B)or vec F = vec F _(E) + vec F _(B)`
When `F _(E) = F _(B) implies | q vec E| = q | vec v xx vec B|`
`qE = qv B sin 90^(@) ` [Taking `theta = 90 ^(@)`]
`implies v = (E)/(B)`