A velocity selector in a mass spectrometer uses an electric field of 4.4 x 105 V/m. What magnetic field strength (in Tesla) is needed to select a speed of 4.8 x 106 m/s

  B = 9.16 10⁻²  T

Explanation:

The speed selector is a configuration where the electric and magnetic force has the opposite direction, which for a specific speed cancel

       q v B = q E

       v = E / B

       B = E / v

Let's calculate

      B = 4.4 10⁵ / 4.8 10⁶

      B = 9.16 10⁻²  T

pythagoras' theorem

square root (-5^2+9^2)

square root (25+81)

square root (106)

angle is tan^-1(9/5)

neg x, pos y