Water Bridge over a River!

[Roby]

 Of course if the boat travels much slower than light otherwise mass does change.  

Oh, so now you want to play quantum mechanics.

Suppose you could travel faster than the speed of light, would it be possible to go around the world so fast that you would arrive back at your starting point and take a picture of yourself before you left.  

Oh, and if things expand when they heat up and contract when they get cold, how come water expands as it freezes into ice.

If you have 1 cup of water and 1 cup of alcohol and you pour them both together, how many cups do you have?

[rolly_wood]

Roby, have I annoyed you in some way?  I was simply trying to participate to the discussion... kiddiing also.
Unfortunately this is not my language and then some 'tones' of what I write may appear to you as teasing or smart @ss (*)... as sometimes the same seems to me in reading others' post.
Of course in that case I assume that I am wrong... what I would ask you is that you may assume that it was not my intention.
I have enough difficulties in explaining what I want to say without using wordplay or hidden meanings...

Otherwise I have no other chance that write in third person simple sentences which cannot be misunderstood.
Hope not so..

going to bed, it's late.

(*) ?

[Roby]

Rolly, I should again apologize to you.  I am not at any time annoyed by you or any of the good persons here on the forum.  Sorry that I come across that way. 

My father was a physics professor, and I was trying to keep everyone's mind working until those at IPP got back.  When you mentioned a subject that was in physics, I could not resist sharing some of the odd puzzles of the universe that I have been exposed to over the years.

I do tease a lot of the guys on the forum, and I am not offended when they tease me back, but I did not think you were teasing or being a smartie.

Give me a chance to start over with you.  I do not want you to feel like I am picking on you.  I promise to be more mindful of the way I say things from now on.

 

[Canuck]

If you have 1 cup of water and 1 cup of alcohol and you pour them both together, how many cups do you have?

'pour them both together'...well if you're pouring them both together on the floor you'd have an empty cup 

[Roby]

If you mix them together and drink them, then you forget what the question was.   

[rolly_wood]

Give me a chance to start over with you. 

No need to start over because nothing happened or ended. It is me who was worried having written something which could have offended you. Happy to know I did not.
I apologize to have misinterpreted the sense of your message. In my turn I promise I will assume you are joking unless you will explicitely say not

why do not we drink to fhe forum with that alcohol ?


PS Waiting the solution of the cannon problem ...  you know, as physicist I am as I were retired, but still like those odd puzzles.

[STP]

I just cracked open a beer, so let me take a stab at the cannon question!

It seems to me the recoil of any gun is related to the mass and acceleration of the projectile - I remember something about a guy named Newton (also inventor of the cake/cookie) that said every action has an equal but opposite reaction.  Thus, the recoil from the firing with a cannon ball should be greater than the firing with no cannon ball.

[rolly_wood]

Thus, the recoil from the firing with a cannon ball should be greater than the firing with no cannon ball.

I would have drawn the same conclusion using the conservation of linear momentum instead (mass times speed). But I suspect there is something further which must be taken into account (the air pressure as the birds in the truck?), otherwise it would not be an 'odd puzzle' ...

[Roby]

why do not we drink to fhe forum with that alcohol ?

Where do you come up with those cute smilie faces.  They are so cool and have such personality. 

 I would say that you both answered correctly about the cannon, even if you used different approaches.  There is nothing more to the puzzle.  I recently saw a movie where a door was smashed open by the recoil of cannon without a ball and figured that the movie directors had not done thier research.
 
These puzzles were just to keep everyone thinking until the boys came back into town, and now it is more important to hear about IPP.  A boat does produce less force on the earth with the moon overhead.  A cup of water mixed with a cup of alcohol will produce around 1 7/8 cup of total volume because on an atomic level, liquid molecules are like sand and have pockets where another snaller molecule can fit.  This would be like having a jar filled with marbles and then dumping in sand.  The sand fits into the jar with the marbles and still exhibits the same volume.

Oh and water expands as it freezes because it froms into crystal structures that take up more space, which is why a container of waterin the freezer will eventually break the jar.  As an interesting side note, hot water actually freezes quicker than cold water, and moving water won't freeze at all.  My dad explained it to me once, but I still don't recall why.
   

[Canuck]

I sent this question to Jerry McFarland, who's also an engineer...here's his reply

"That's a pretty interesting bridge, I never heard of such a thing.  The bridge must be able to withstand the weight of the water at a given height whether there is one boat or many.  I suspect they just control the height of the water, you could replace each boat with the weight of the water it displaces.  My theory anyway."

Jerry

[gibell]

I noticed a red line in the water on the bridge.  Perhaps the bridge is rated up to this line?  If the water ever goes above this level, due to increased flow or the presence of a boat, the bridge fails!!??  

And what happens in the winter?  Do they have to drain it?  Wouldn't ice freezing and refreezing break it otherwise?  It gets pretty cold in Germany.

Or maybe it becomes an ice skating bridge??