Filling water cup/bucket: which way is faster?

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Discussion Overview

The discussion revolves around the question of which method is faster for filling a water cup or bucket from a hose, considering factors such as distance from the water source, pressure, and flow rate. Participants explore both theoretical and practical aspects of this phenomenon.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that bringing the cup closer to the water source will result in faster filling, while others question the visibility of this effect in practical scenarios.
  • One participant mentions that the flow rate from the tap is constant, implying that the time to fill a cup remains the same regardless of distance, provided all water goes in.
  • Concerns are raised about how the pressure at the bottom of a bucket may affect flow rate when using a hose, particularly if the hose end is submerged.
  • Participants discuss the impact of source pressure and friction in the supply pipe on the filling rate, noting that these factors could influence the outcome.
  • There is a mention of the siphon effect and how it may or may not compensate for friction in the hose, with some participants seeking clarification on its relevance.
  • Some participants propose that the length of the hose may affect the flow rate, with theoretical predictions suggesting that a longer hose could increase fill time.
  • One participant emphasizes the need for experimental testing to validate theoretical predictions regarding flow rates and filling times.

Areas of Agreement / Disagreement

Participants express a mix of agreement and disagreement, with some supporting the idea that distance affects filling time while others argue it does not. The discussion remains unresolved regarding the influence of various factors such as pressure, hose length, and flow rate on the filling process.

Contextual Notes

Participants note that assumptions about constant flow rates and negligible friction may not hold in all scenarios, and the discussion highlights the complexity of the factors involved in the filling process.

  • #31
rugerts said:
This came to mind when I was filling up my cup at the dining hall and there are people behind me waiting. I was wondering that if before I turned the water on, I brought the cup closer to the tap source (which is pretty constant) if this would result in my cup being full (full meaning "pretty much" to the brim, assume no spilling) in a less amount of time.
Ah.

You'll shave about 1/5th of a second off your time - If you don't squander that 0.2s getting the cup into position. Do you think you can move it into position in 1/5th of a second?

Remember: it isn't about how fast you fill your cup - the clock starts the moment the guy in front of you steps out of your way - and stops the moment you step out of the way.
 
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  • #32
Thank you all for the patience and great in depth replies. I think I'm satisfied with the answers now.
 
  • #33
rugerts said:
What if we placed the glass at a low point and raised it as it was being filled at a relatively constant upward velocity; would this be even better than the abrupt bringing up?

Technically of course, you should bring the glass to the top just as the water stream ends, and wait 'til the last moment before bringing it up to get the full advantage of the open-siphon effect, but a bit of showmanship might be achieved by smoothly bringing it up and catching the last drop in mid-air aways below the faucet.

In either case the important bit is keeping a straight face and seeing how long it takes before somebody asks what the heck you're doing.
 
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