The quickest way to fill a glass

It was never said that it couldn't spill, just that it wouldn't foam. Thus, with a high pressure of water entering a glass vertically, you are guaranteed that some if not a lot of water will funnel back out vertically, try it at home.
The angle of the glass slows down the speed of the water by spreading it across more area without reducing the flow.

Originally posted by agryson
It was never said that it couldn't spill, just that it wouldn't foam. Thus, with a high pressure of water entering a glass vertically, you are guaranteed that some if not a lot of water will funnel back out vertically, try it at home.
The angle of the glass slows down the speed of the water by spreading it across more area without reducing the flow.

If you can turn it on full blast, then it's not going to spill out. Full blast on a tap will certainly make the water splash.

Originally posted by uzless
(assume it would fill without foaming so you can turn it on full blast)

If by this the question means the lack of foaming is the reason you can turn it on full blast (my interpretation) then it says nothing about spilling.
If by this the question means that there is no way you can spill the water (your interpretation) than of course it makes no difference how the glass is held. Neither interpretation can be said to be the 'right one' but at least the second interpretation leads to a more satisfying question.

edit... I posted within uzless's quote! sorry about that.

I meant that no matter how you fill it, none will splash out.


Anyway, the fastest way is to turn the faucet on. The timer would start as soon as you start to fill the glass.

So, you'd put the glass under the faucet so the glass is touching the bottom of the sink. Once you get the glass under the stream of water, you'd raise the glass right up to the faucet. This way you capture all of the water within the stream sooner, rather than having to wait for it to fill up by gravity.

Hmm, in that case, hats off to you a thousand young.

Originally posted by agryson
Hmm, in that case, hats off to you a thousand young.

You could improve the time by starting with the glass low and moving it upwards so that the flow of water is temporarily increased.

Originally posted by uzless
I meant that no matter how you fill it, none will splash out.


Anyway, the fastest way is to turn the faucet on. The timer would start as soon as you start to fill the glass.

So, you'd put the glass under the faucet so the glass is touching the bottom of the sink. Once you get the glass under the stream of water, you'd raise the glass right up to the ...[text shortened]... f the water within the stream sooner, rather than having to wait for it to fill up by gravity.

You're right. Raising it up would save you a second or some fraction thereof.

Wait - what if you put the glass right up to the faucet? Wouldn't this give the same result as if you raised it from a low point?

Originally posted by AThousandYoung
You're right. Raising it up would save you a second or some fraction thereof.

Wait - what if you put the glass right up to the faucet? Wouldn't this give the same result as if you raised it from a low point?

And don't forget about the time lost while the water is flowing down before it gets to the glass, seems it would be a wash if you considered that. Suppose the spout was 100 meters higher than the glass, the time delay would be considerable. If it was one meter below the spout, the water would for sure get there faster but still it would have to travel that one meter before getting to the glass therefore delaying the fill.

If we're assuming no spill ( >🙁 ) then...
Flow is a measure of volume per unit time. Since our flow from the tap is constant, and the volume to fill is constant, the time it takes for that volume to get out of the tap is also constant.
Raising the glass or keeping it pressed up to faucet makes no difference.

Edit... the height problem, if we assume the flow is fast enough to keep the stream of water cylindrical, and we know the radius of the outlet, we can calculate the cylinder whose height gives exactly the volume of water needed. All we need do is keep the bottom of the glass at or above this distance from the tap. (Even if it's not cylindrical, the same method can be used to calculate the height for cones, streams of droplets etc. the cylinder is just a simplification to demonstrate.)

Originally posted by AThousandYoung
You're right. Raising it up would save you a second or some fraction thereof.

Wait - what if you put the glass right up to the faucet? Wouldn't this give the same result as if you raised it from a low point?

putting it directly at the faucet outlet means you don't capture any of the water column as you would if you raised the glass up from the bottom. (keep in mind the timer starts when you put the glass under the faucet, not when the faucet is turned on)

You would have to wait for the water to come out of the tap whereas as by lifting the glass, you capture all the water that has already come out of the faucet.

This extra amount of water would be proportional to the height that you can raise the glass. (the distance from the sink to the faucet)

Originally posted by uzless
putting it directly at the faucet outlet means you don't capture any of the water column as you would if you raised the glass up from the bottom. (keep in mind the timer starts when you put the glass under the faucet, not when the faucet is turned on)

You would have to wait for the water to come out of the tap whereas as by lifting the glass, you capture ...[text shortened]... rtional to the height that you can raise the glass. (the distance from the sink to the faucet)

True but wasteful.

But if the tap was under water it would fill lots quicker, no foaming, splash back or spill

Originally posted by iraqi insurgent
But if the tap was under water it would fill lots quicker, no foaming, splash back or spill

No, there would be additional back pressure from the surrounding fluid.

Originally posted by uzless
You have an empty glass in one hand, the faucet knob in the other. The faucet is not turned on.

If someone was timing you, how could you fill the glass the fastest? (assume it would fill without foaming so you can turn it on full blast)

Would you lift the glass up and down? Does it make any difference?

You guys are all "full" of hot "air". Isn't the glass already "filled" to begin with? unless of course we are assuming its in a vaccum and we want to fill the glass with water....

When does the time start? could you fill the sink and then plunge in the glass? .....