So a ball is dropped from a roof, passing a window 1.2 m tall. It takes 1.25s to pass the said window. It takes 1 more second below the window before it hits the ground. How tall is the building?

, where is the starting velocity, is the distance, is the time, and is the acceleration.

Therefore, , or

for the starting velocity when it passes the top of the window.But this results in -5.165, which isn't possible unless down is taken to be negative, which it isn't.

I completed the problem without realizing this, only substituting a variable,z, for this number.

Another formula gave me the time taken to travel the distance above the window: , where, this time, v is the starting speed when it was dropped (0).

Then we add all the times together to find the total fall time, , which, for simplicity, we will callb.

Then the last formula we use is , which i think is the same one we used earlier. this gives us

but it's supposed to be 20.4

thanks to anyone who helps!