Pressure in Closed Tank | Is the Author Wrong?

[foo9008]

Homework Statement

in this question , the author stated that the P1 = P atm , but at point 1 , the gas tank is not open to the atmosphere, it is a closed tank . so , is the author wrong ? again , at point 2 , the tank isn't open to atmosphere, why it is P2= P atm ?

Homework Equations

The Attempt at a Solution

 

[gneill]

Why might the two pressures be P atm? Can you think of any reason? How does the small diameter hose reach the liquids?

 

[foo9008]

Why might the two pressures be P atm? Can you think of any reason? How does the small diameter hose reach the liquids?

i don't think P1 and P2 = P atm ...

 

[gneill]

i don't think P1 and P2 = P atm ...

I understand that. But can you think of any way that they could?

 

[foo9008]

I understand that. But can you think of any way that they could?

for P1 = P2 = P atm , the tank is not closed?

 

[gneill]

for P1 = P2 = P atm , the tank is not closed?

Correct. How does the hose enter each tank?

 

[foo9008]

Correct. How does the hose enter each tank?

View attachment 98796

at point 1 , it is immersed in the gas tank , while the point 2 is at the hole only , not completely immersed . What are you trying to tell ?

 

[gneill]

at point 1 , it is immersed in the gas tank , while the point 2 is at the hole only , not completely immersed . What are you trying to tell ?

I'm pointing out that neither tank is sealed. Both are open to the atmosphere through their filling apertures. The siphon hose does not make an air-tight seal at either opening.

 

[foo9008]

I'm pointing out that neither tank is sealed. Both are open to the atmosphere through their filling apertures. The siphon hose does not make an air-tight seal at either opening.

if that is air-tight selaed , then the pressure acting would not be P atm anymore , am i right ?

 

[gneill]

if that is air-tight selaed , then the pressure acting would not be P atm anymore , am i right ?

Sure. It might start out at P atm at the moment a seal was made though.

But there is no seal mentioned in the problem statement. The assumption is that, as in the real-life situation for siphoning gas in this manner, the hose fits loosely through the gas cap opening and down into the liquid.