Physics/mechanics, forces accelaration

[gaz3992]

Homework Statement

A ball is thrown horizontal out of a window 18m above the ground. it is thrown horizontally at 5.0ms. show that it takes about 2 seconds to drop.

Homework Equations

S=ut+1/2at^2

The Attempt at a Solution

u=0
a=9.8
s=18
18=0t+1/2*9.8t^2
36=9.8t^2
sqrt3.6734=t
t=1.92

is this near enough too 2 to be the right answer or have i made a mistake some where i was not sure if the horizontal force would have any effect on the time taken to drop. Any help would be much appreciated.

 

[Stonebridge]

That's perfect. 1.92 is certainly "about 2 seconds" in anyone's book!
The horizontal component of the ball's motion is independent of the vertical, gravitational, component; so your method is fine.
(That horizontal velocity of 5m/s doesn't come into this calculation, but is probably needed for further calculations, such as how far away from the window does the ball land?)

Oh, and welcome to Physics Forums!

 

[gaz3992]

Thanks i just needed conformation because i got to the answer partially using trial and error to find the right method and I'm impressed you managed to guess the exact next question on the paper.