# Homework Help: Basic Two Dimensional Problem.

1. Sep 9, 2009

### Aquas

Hey, everyone! Glad I found this forum, I plan to be using it a lot to try to expand my Knowledge, I currently taking an AP Physics class in my high school with no prior physics experience. The teacher however is really great! Anyway lets see what we got going here.
(Note ▲=Delta)
1. The problem statement, all variables and given/known data

A ball is thrown horizontally from the roof of a building 58 m tall and lands 50 m from the base. What was the ball's initial speed?

Vertical Known
▲Y=-58
A Sub Y = -9.8m/s
t=5.918s
VnotY=?

Horizontal Known
▲X=50m
VnotX= ?

2. Relevant equations
t=5.918
I got this because assuming that the distance of 58m was traveled going a speed of -9.8m/s (g) it equals 5.918! (Hopefully)

3. The attempt at a solution
Its a long shot but I attempted to compare it to a problem done in school which was essentially the same but, involved an angle of the stone coming off the roof. Also different Knows were given. So this was my go

&delta Y=(VnotX)(t)² + (.5)(g)(t)² I put in what I know

-58=(VnotY)(5.91)² + (4.9)(5.91)² Attempted to solve for VnotY

-58=(VnotY)(34.9281) + (171.14)

(VnotY)=(34.9281)+(229.14) I added the -58 over

(VnotY)=264.07 : ( I dont think this is right...

So that is where I am, I may be completely off...

Ok! So I looked at the problem again found an Inherent flaw,

▲y=(VnotY)(t)+(.5)(g)(t)²

SO! It turns out (VnotY) is Zero...Making that all Null and void...
So with some Algebra Magic I get t=3.43! With this I hope to get further...Will keep posted!

Another Update!!!
While looking through my book found that while somthing is in free fall it has 0 Acceleration in the X-Axis! So that voids Half of the Equation!! Woo Go Physics! Making it simple and I found that the initial speed was 14.57

Last edited: Sep 9, 2009
2. Sep 10, 2009

well done!