Question

A ball is projected horizontally from the top of a building 19.6m high.if the line joining the point of projection to the point where it hits the ground makes an angle of 45° to the horizontal what is the initial velocity of the ball

Answer 1

You want the ball to land 19.6m from the wall.

So, how long does it take to fall 19.6m?
That would be 2 seconds.

So, what horizontal speed does it take to travel 19.6m in 2s?