# Could a thing contain more than its volume can w/o overflowing?

1. Mar 18, 2015

### pie

Hey, I am new in this forum and looking forward to learn physics which I hate :)

My first question concerns possibility, in theory. Say, there is a water tank. Let us say that we made a nanometer hole. The tank is full. Then, we put even more water through that hole. But the hole has something that closes very, very fast. So,

1. Could the water still be in the tank?

2. And if yes, what is going to happen then?

2. Mar 18, 2015

### Staff: Mentor

Water is essentially incompressible, so if the tank is full, how do you propose putting more water in, regardless of the size of the hole?

3. Mar 18, 2015

### Staff: Mentor

If the tank is sealed then you won't be able to put more water into the tank than it already had. If it's not sealed then it will begin to overflow.

4. Mar 19, 2015

### Khashishi

Either the tank starts to bulge out or it bursts. Or, if the tank is immensely strong, you can compress the water under extreme pressures.

5. Mar 19, 2015

### sophiecentaur

I guess you could imagine a compression wave entering the hole, which could be closed before it has a chance to bounce back after reflection inside the tank. This would assume an infinitely strong container but real water - which is slightly compressible.
I must say, I don't like these 'immovable object and irresistible force' questions. They usually emerge from real world problems, where nothing is ideal. So it would be more fruitful to grasp the nettle and address the real world problem at the start. We often get posts about electrical circuits with short circuits and perfect batteries. The thread goes round and round in circles and gets nowhere.
Choosing where and when you can validly assume infinities and zeros in Physics requires a lot of care. (Or bitter experience)

6. Mar 19, 2015

### Integral

Staff Emeritus
I do this nearly everyday. We have a 16" naval gun shell standing on its nose. Where the fuse used to be we have inputs for a high pressure pump. I fill the "bom" with water and oceanographic research instrumentation. Then via the high pressure pump I proceed to shove more water into the already full test vessel. If I force in about an extra liter of water we get internal pressures of about 8800psi. or 6000m of water depth.
Since water is nearly incompressible, how can we push more water into the test vessel? It is composed of high strength steel (2" thick at the thin spots) which is being expanded by the high pressure water.

7. Mar 19, 2015

### sophiecentaur

It's interesting to consider the stored energy when you pressurise a vessel. When they pressure test gas storage cylinders, it's common to use water, pumped at a few hundred atmospheres, rather than air because there is very little energy involved in pressurising the water (pressure times volume change), compared with when you pump it full of air ( several m3 of air, to start with). If the cylinder fails the 'wet test' it will just split and vent the pressure easily, with very little 'work done'. If it fails when full of air, it's a serious bomb.