A Proton Moving at 3 × 10⁴ M/s Is Projected

Short Answer

A proton moving at 3 × 10⁴ m/s is projected at an angle of 30° above a horizontal plane. If an electric field of 400 N/C is directed downwards, how long does it take the proton to return to the horizontal plane? (HINT: Ignore gravity.) [mProton = 1.67 × 10⁻²⁷ kg, qProton = +1.6 × 10⁻¹⁹ C.]