Homework Help: Firefighter problem

1. Oct 1, 2011

barthayn

1. The problem statement, all variables and given/known data

A firefighter on the street is trying to spray water from a hose to a building a horizontal distance x1 through a window a height h above the height of the hose (see figure in image below). For a given initial speed vo of water from the hose, we would like to future out if the water will reach the window, and if it does, then what angle (and how many angles are there) does he need to aim the hose at. (The questions are in the image below)

http://img10.imageshack.us/img10/1237/firefighter.th.gif [Broken]

2. Relevant equations

t = d / (v cos θ)
h = -4.9 sin θ t^2 + v sin θ t

3. The attempt at a solution

I tried subbing in the horizontal time equation for t in the vertical displacement equation. But no luck for a. Any hints on how to prove the equation for a?

Last edited by a moderator: May 5, 2017
2. Oct 1, 2011

barthayn

Update.

I proved the question for a. It turns out that I forgot that a/a = 1 and not equal to 0 (lol)

How do I do b. I don't understand how you can solve for the angle that it can be equal to to give you only one angle that you have to use so that the water can enter into the window when there are so many unknowns. Any hints?

Last edited: Oct 1, 2011