Question

A ball is thrown upward off the top of a 30-meter high building. 10 meters below the top of the roof, is the top of a window, which is 2 meters high. How long (time) does it take for the ball to pass from top to bottom of the window?

What I have so far is:

-10 = v(initial) t - 4.9 t^2
-12 = v(initial) t - 4.9 t^2

How do I solve this question if I don't even have initial velocity?

Answer 1

"How do I solve this question if I don't even have initial velocity? "
You are quite right. You need additional information, for example maximum height attained, time it took to come back to the top of the roof, initial velocity, etc.

On the other hand, the height of the building (30m) is immaterial.