A proton with mass 1.67 x 10−27 kg and charge +1.6. x 10−19 C, is sent with velocity 2.3 x 104 m/s in the +x direction into a region where there is a uniform electric field of magnitude 780 V/m in the +y direction. What must be the magnitude and direction of the uniform magnetic field in the region if the proton is to pass through undeflected?
Assume that the magnetic field has no x-component and neglect gravitational effects.