• # question_answer A plane flying horizontally at a height of 1500 meters with a speed of 200 meter/second passes directly over an aircraft gun. Then the angle with the horizontal at which the shell should be fired from the gun with a muzzle velocity of 400 meters per second to hit the plane is: A) $90{}^\circ$B) $60{}^\circ$C)   $30{}^\circ$D)   $45{}^\circ$

Let the shell hit the plane at the point B after time t (figure) $200\,t={{v}_{0}}\cos \theta \times t$ $\cos \theta =\frac{200}{{{v}_{0}}}=\frac{200}{400}=\frac{1}{2}$ $\therefore$    $\theta ={{60}^{o}}$ Hence, the correction option is (d).