Question

A rock is dropped from the top of a 45-meter tower, and at the same time a ball is thrown from the top of the tower in a horizontal direction. Air resistance is negligible. The ball and the rock hit the level ground a distance of 30 meters apart. The horizontal velocity of the ball thrown was most nearly 

(A) 5 m/s 

(B) 10 m/s 

(C) 14.1 m/s 

(D) 20 m/s 

(E) 28.3 m/s

Answer 1

Correct option (B) 10 m/s

From a height of 45m (= ½ gt²) it takes 3 seconds to strike the ground. In that time, the ball  thrown traveled 30m. v = d/t