A Proton Moving at 3 * 104 M/s Is Projected $\degree$

Short Answer

A proton moving at 3 * 104 m/s is projected at an angle of 30 $\degree$ 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.]