Question

A target T lies flat on the ground 3 m from the side of a building that is 10 m tall, as shown above. A student rolls a ball off the horizontal roof of the building in the direction of the target. Air resistance is negligible. The horizontal speed with which the ball must leave the roof if it is to strike the target is most nearly

(A) 3/10m/s

(B) √2m/s

(C) 3/√2m/s

(D) 3m/s

(E) 10√(5/3)m/s

Answer 1

Correct option (C) 3/√2m/s

For a horizontal projectile, the initial speed does not affect the time in the air. Use v_0y = 0 with 10m = ½ gt² to get t = √2 For the horzontal part of the motion; v = d/t