- #1

tuki

- 19

- 1

## Homework Statement

Fire hose has diameter of 4.0 cm and flow rate of 10 L/s. There is pressure of 2.2 bar inside the hose. How high the water can go at best? Water density is 1.00E3 kg/m^3 and air pressure outside the hose is 1.0 bar.

## Homework Equations

Flow rate

$$ Q = Av $$

Newtons equations?

## The Attempt at a Solution

I tired to find speed for water particle when it exits the hose. I can get speed directly from flow rate.

$$ v = \frac{Q}{A} = \frac{Q}{(\frac{d}{2})^2 \pi} $$

$$ v \approx 7.957 \text{ m/s} $$

If we would aim the hose at 45 angle it would follow height as function of time as:

$$ h(t) = vt-gt^2 $$

i solved the maxima with first derivative $$ t = \frac{v}{2g} \approx 0.4055 \text{ s} $$

then you would compute the height from the function $$ h(0.41\text{ s}) \approx 1.6 \text{ m} $$

However the correct answer should be 26m. What I'am doing wrong?