## Poll

5 members have voted

USpapergames
Joined: Jun 23, 2020
• Posts: 687
July 31st, 2020 at 9:50:10 PM permalink
Quote: charliepatrick

I suspect this is fluid dynamics and is what we covered in second year degree, but can't remember any details. - btw if Dr Goddard ever reads this, thanks for your help. I'm sure there are people, such as gas pipe analysts, who rely on fluid dynamics, but suspect the typical WoV reader doesn't use it.

I probably didn't manage to understand the exact details but I'm guessing the puzzle is about a sphere of unit radius falling vertically. It currently has its centre at (0,0,z) (z=1: so just touching the surface; z=0: has dropped further?) and is travelling at 10 m/s (since there's reference to .1 second, terrminal velocity and g is about 10m/s^2) and then asking how a flat body of liquid/water (formerly z<=0) would be displaced.

Puzzles are supposed to be fun and the really good ones have an ahh! moment or use logic rather than mathematics. Personally I tend to ignore the ones where you need to do non-trivial integration or the like. So I will be passing on this one.

Actually at 10ms the spheres center is at 0,0,1 and the circumference of the sphere is touching 0,0,0 | 0,0,2 | 1,0,1 | 0,1,1 | -1,0,1 | 0,-1,0
Math is the only true form of knowledge
USpapergames
Joined: Jun 23, 2020
• Posts: 687
July 31st, 2020 at 9:58:09 PM permalink
Quote: gordonm888

Quote: charliepatrick

I suspect this is fluid dynamics and is what we covered in second year degree, but can't remember any details. - btw if Dr Goddard ever reads this, thanks for your help. I'm sure there are people, such as gas pipe analysts, who rely on fluid dynamics, but suspect the typical WoV reader doesn't use it.

I probably didn't manage to understand the exact details but I'm guessing the puzzle is about a sphere of unit radius falling vertically. It currently has its centre at (0,0,z) (z=1: so just touching the surface; z=0: has dropped further?) and is travelling at 10 m/s (since there's reference to .1 second, terrminal velocity and g is about 10m/s^2) and then asking how a flat body of liquid/water (formerly z<=0) would be displaced.

Puzzles are supposed to be fun and the really good ones have an ahh! moment or use logic rather than mathematics. Personally I tend to ignore the ones where you need to do non-trivial integration or the like. So I will be passing on this one.

Actually, from the problem statement, the sphere's x,y position is not 0,0 but x,y! And, I'm not sure about your interpretation of the reference to terminal velocity; its not clear to me that the sphere isn't moving downward at the start of the problem. Also, falling for 0.1 sec the sphere's velocity would be about 1 m/s, not 10 m/s.

Other than that, I do agree with everything you are saying. If I want fluid dynamics problems, I can look in textbooks on my shelf. But . . .actually . . . I don't want fluid dynamics problems, lol.

This is a gambling forum, and, IMO, puzzles involving number theory, combinatorial math, geometry and logic are particularly suitable.

Also, anyone posing a "math puzzle" to the forum should put sufficient work into the puzzle statement such that it is clear, sufficient in its information and reduces the chance of misinterpretation to a minimum.

The sphere must be moving downward or else it won't be accelerating at terminal velocity. Terminal velocity all defines the direction of movement since the force is gravity and we can assume the body of water is towards the direction of the earth where the sphere is accelerating towards prior to impact. Something must be moving at a different rate in order to obtain any velocity. Think of the data collecting cube as it can only capturing data upon impact and only for a specific instance in time and it happens to have a 10-millisecond delay.
Math is the only true form of knowledge
Wizard
Joined: Oct 14, 2009
• Posts: 22432
July 31st, 2020 at 10:25:24 PM permalink
Can anyone translate this question into plain simple English?
It's not whether you win or lose; it's whether or not you had a good bet.
USpapergames
Joined: Jun 23, 2020
• Posts: 687
July 31st, 2020 at 10:53:52 PM permalink
Quote: charliepatrick

I suspect this is fluid dynamics and is what we covered in second year degree, but can't remember any details. - btw if Dr Goddard ever reads this, thanks for your help. I'm sure there are people, such as gas pipe analysts, who rely on fluid dynamics, but suspect the typical WoV reader doesn't use it.

I probably didn't manage to understand the exact details but I'm guessing the puzzle is about a sphere of unit radius falling vertically. It currently has its centre at (0,0,z) (z=1: so just touching the surface; z=0: has dropped further?) and is travelling at 10 m/s (since there's reference to .1 second, terrminal velocity and g is about 10m/s^2) and then asking how a flat body of liquid/water (formerly z<=0) would be displaced.

Puzzles are supposed to be fun and the really good ones have an ahh! moment or use logic rather than mathematics. Personally I tend to ignore the ones where you need to do non-trivial integration or the like. So I will be passing on this one.

I agree with you about puzzles needing to be fun and I will rethink my next puzzle but there is in fact a Reika moment to this. I need to post a picture that will explain everything but I don't know how to post it on this form but I've seen other people do it.
Math is the only true form of knowledge
USpapergames
Joined: Jun 23, 2020
• Posts: 687
July 31st, 2020 at 11:22:29 PM permalink
Hint #3 How much energy is in water and how much energy over the surface area is required to get a water displacement with ripples of the lengths of distances apparent within the expression? We know the vector fields of water motion are all traveling away from the point of impact.

Hint #4 Objects accelerating weigh heavier than stationary objects so I will definitely accept any answer in any measurement of energy which also means I will accept any measurement of mass as well, but to make the question even easier I will accept any comparative measurement of density and we can then assume that the sphere has evenly proportional of weight throughout its volume; even though this assumption is not needed to derive to a statistical solution.
Math is the only true form of knowledge
USpapergames
Joined: Jun 23, 2020
• Posts: 687
August 1st, 2020 at 5:22:49 PM permalink
I see, there are a lot of different equations for expressing flow rate.

https://www.pipeflowcalculations.com/pipe-valve-fitting-flow/flow-in-pipes.xhtml

I'm using the equation for fluid flow of an average velocity & pipe diameter for known flow rate. I did not take blood viscosity into the equation.
Math is the only true form of knowledge
Wizard
Joined: Oct 14, 2009
• Posts: 22432
August 1st, 2020 at 8:50:49 PM permalink
Posts about my question on the stent/liquid flow through a pipe have been moved to Stent math puzzle.
It's not whether you win or lose; it's whether or not you had a good bet.
USpapergames
Joined: Jun 23, 2020
• Posts: 687
August 3rd, 2020 at 9:48:06 AM permalink
So only person attempts to answer the question :/ So I guess I will post an even more difficult question :)
Math is the only true form of knowledge
gordonm888
Joined: Feb 18, 2015
• Posts: 2728
August 3rd, 2020 at 11:58:49 AM permalink
Quote: USpapergames

So only person attempts to answer the question :/ So I guess I will post an even more difficult question :)

I am the one person who posted an attempted answer to your question. I have degrees in Physics and Nuclear Engineering and I think my background helped me to think about your problem. But I would encourage you to think about the advice that several of us have offered. Textbooks in all technical fields are full of very difficult problems but the vast majority of those problems would not be a good match for this forum. This is principally a gambling forum where problems in logic, number theory, combinatorial math, geometry and trigonometry. etc. have been popular. And, maybe statistics. We can handle other topics, too, but choose wisely.

You seem like a very bright guy and I would like to see you have a good experience with this forum, so that you will stay as an active member! I am trying to help.
So many better men, a few of them friends, are dead. And a thousand thousand slimy things live on, and so do I.