# Tag Info

Accepted

### Reverse blood flow in an IV

I'm not a nurse, but I think that the pressure into the vein is enough, if you see the blood flowing from the vein to the outside. This should mean that, locally, close to the needle, a small amount ...
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### Is the saying "fluid always flows from high pressure to low pressure" wrong?

No. Fluids in general do not flow strictly from points where pressure is high to points where pressure is low. Even in the simplest static case (which is a reasonable first approximation for blood), ...
• 1,012
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### How does a bottle pour its contents?

You need an air intake to level the pressure, which would otherwise drop and stop the outflow if you don't replace the lost volume of fluid in the container by air. (And btw. the tea pot sitting on my ...
• 3,206
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### Will just the increase in height of water column increase pressure or does mass play any role in it?

At first, the conclusion seems absurd. You have a tank, which is open at the top of the pipe, that is comfortably holding 1000 L of water. Then you add just 1 L more, albeit in an unusual shape, and ...
• 494
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### If a container of water from some depth is brought to the surface, what would be the pressure in the container?

That depends on the compressibility of the medium and the rigidity of the container. Let's first look at a highly compressible medium like air before I answer you question regarding water. Fill your ...
• 2,864

### How does pressure exist inside a drop of water?

The pressure outside a droplet arises from molecules bouncing against the droplet's surface, delivering an inward momentum "kick." Since the droplet doesn't shrink to nothing, there must be ...
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### How was the Titan submersible implosion time calculated?

We could estimate a lower bound for the hull collapse duration through a scaling argument: Consider the acceleration of a suddenly detached small portion of the hull (with area $A$ exposed to the sea ...
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### Is the saying "fluid always flows from high pressure to low pressure" wrong?

As you pointed out, the force is directed from the regions of high pressure towards the low pressure, and, according to the Newton's second law, this is where the acceleration is directed. This does ...
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### The actual proof of $\delta W = P dV$

$$\delta W=F\delta x=F\frac{\delta V}A=\frac FA\delta V=P\delta V$$
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### Is the saying "fluid always flows from high pressure to low pressure" wrong?

The question has been answered already but since the OP mentions the Bernoulli equation it is instructive to see how this equation actually explains flow against pressure. Bernoulli's equation governs ...
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### Liquid pressure at the atomic level

First let me note that technically, even within your argument, the collision velocity could be higher or the collision frequency could be higher. Hence pressure in a gas is proportional to temperature ...
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### Is temperature held fixed in this derivative for pressure?

Strictly speaking, as discussed in Themis' answer, $-P$ is the partial derivative of the internal energy with respect to volume at fixed entropy. However, in the case of the electron gas in typical ...
Accepted

### Would different sounds of the same intensity but different frequencies have the same harmful effect on the human ear?

Introduction I don't think this is so simple as to be answered with a "yes" or "no". The hearing system is rather complex on its own and comprises of both mechanical and "...
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### What is pressure energy in a closed system?

This increase in pressure seems to store energy, like a compressed spring. It seems to, but for an ideal gas, it doesn’t (store internal energy, that is); it stores negative entropy in the form of a ...
• 24.7k
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### Help me understand extreme pressure

TLDR: To understand it, don't think about pressure. Think about energy. The best approach here is to think in terms of energy/work, instead of pressure. There's lots of situations that become more ...
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### What is the underlying concept in case of finding pressure inside a balloon kept at some height in atmosphere?

If the volume of the balloon is not changing then the net force acting on any part of its shell is zero. If we neglect the forces applied upon the part of the shell by the nearby shell parts (the ...

### Is the saying "fluid always flows from high pressure to low pressure" wrong?

I don't know much about blood circulation and just give some basics of steady state fluid mechanics. Poiseuille was a physilogist who was interested in the circulation in blood capillaries. In the ...
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