A target lies flat on the ground 4 m from the side of a building that is 10 m tall, as shown below.

The acceleration of gravity is 10 m/s2 . Air resistance is negligible.
A student rolls a 4 kg ball off the horizontal roof of the building in the direction of the target. The horizontal speed v with which the ball must leave the roof if it is to strike the target is most nearly

1 answer

How long to fall 10 meters?
10 = (1/2)(10) t^2
solve for t, time in air
then
4 meters = u t
solve foe u