An arrow was fired horizontally from a platform above the ground. Exactly 3 sec after it was released, it struck the ground at an angle of 45o from the horizontal.

Question

1) With what speed and from what height was it launched?

Answer 1

fired horizontally.
That means the horizontal speed at impace=vertical speed.
Vertical speed:
vf=9.8*3
so launch speed is that.
Now, platform height.
h=1/2 (9.8)3^2