with what velocity must a ball be thrown in order to achieve the height of 50 ft.? and how long will it stay in the air?

Answer 1

Equations of motion

v=u+at
v^2=u^2+2aS
S=ut+(1/2)*at^2

u = initial velocity
v = final velocity
t = time
a = acceleration
S = displacement.

Once you know 3 out of the 5 you can find the other two. See if you can write down 3 things you know about the situation.