A Proton Moving at 3

Multiple Choice

A proton moving at 3.0 × 10⁴ m/s is projected at an angle of 30° above a horizontal plane.If an electric field of 400 N/C is acting down,how long does it take the proton to return to the horizontal plane? (Hint: Ignore gravity.m_proton = 1.67 × 10−²⁷ kg,q_proton = 1.6 × 10−¹⁹ C)

A) 7.8 × 10−⁷ s
B) 1.7 × 10−⁶ s
C) 3.9 × 10−⁶ s
D) 7.8 × 10−⁶ s