Tank and a hole in it whats the speed?

[brunettegurl]

tank and a hole in it what's the speed??

Homework Statement

A careless worker at a refinery accidentally punches a hole in a gasoline tank 47.4 m below the surface of the gasoline. The tank had been sealed under 3.07 atm of absolute pressure and the density of the liquid is 659 kg/m3.If the hole is 17.1 m above the ground and the pressure outside the tank is 1.00 atm, determine the speed at which the gasoline exits the hole.

Homework Equations

P1+ $$\rho$$gh+0.5*$$\rho$$V²=P2+$$\rho$$gh+o.5*$$\rho$$V²

The Attempt at a Solution

i tried to solve using the above question but i can't determine which number to use as height..pls. help

 

[ideasrule]

It doesn't matter what you use for the height; just pick a reference level--that is, a point where you define h to be 0--and stick with it. The reference level can be the ground, the hole, or even the top of the gasoline. It doesn't matter as long as you remember that h is negative for heights below the reference level.

 

[PhanthomJay]

Something to ponder...would you expect the exit speed of the gas to be different if the tank were punctured on the Rocky Mountains at elevation 5000 feet as opposed to being punctured on the Hawaiian Islands at elevation 0?

 

[brunettegurl]

yes wouldn't the different atmosphere pressure effect the speed that it come out in??

 

[PhanthomJay]

yes wouldn't the different atmosphere pressure effect the speed that it come out in??

Yes, nice pondering. Also g would vary slightly. But what about the value of h to use? Do you agree with Ideasrules post?
Edit: I just noticed your equation does not include the use of subscripts for h1 and V1 on the left side of the = sign, and h2 and V2 on the right. I just want to be sure you are aware of that.

 

[brunettegurl]

my main problem is i don't know which value to use as my h1 and so on... i know i have to solve v2. i know my p1=3.07atm and p2=1atm...and if i just randomly choose a pt as h won't the answer change accordingly??

 

[PhanthomJay]

my main problem is i don't know which value to use as my h1 and so on... i know i have to solve v2. i know my p1=3.07atm and p2=1atm...and if i just randomly choose a pt as h won't the answer change accordingly??

No, as ideasrule point out, it won't matter. It's (h1-h2) that counts, which always comes out to the same value of 47.4 no matter what level of reference you use.

 

[brunettegurl]

thanx that was my main problem..i got the answer