Question

a ball thrown horizontally from a point 40m above the ground,strikes the ground after traveling a distance of 9m. with what speed was it thrown? use g=10m/s^2

first i need to find the time so I used y=y_0 +v_0t +1/2at^2
-40=-1/2(10)t^2
t=8s

then x=x_o+vt
9=v(8)
v=1.125m/s

Is this correct?

Answer 1

No.
t= sqrt 8

then proceed to the second part with the right time.