Another Physics Brain Teaser

Mr Overboard

I was working on the assumption that since pee is water based that it would mix in with the bath water and change the density of the bath water. I could be a wee bit wrong.

 

Often comes as a surprise to people when you point out that Mooring weights get lighter by the amount of water they displace.

I'm always amazed just how much intuition with bouyancy and fluids that folk get wrong. Pressure goes up with depth and a classic misconception is that bouyancy increases with depth ( it does actually but that's temperature related ) So here another question;

Why does a submarine when it trims have to lighten itself more the deeper it goes? (neglecting temperature and related density issues).

 

I know this one!
But I'm not going to tell, yet. (it seems a bit unfair, as it's my job!).

 

Mike I hate to say it but I don't really care - out and out 'skimmer' me! PI will explain!!

 

There are two types of sea going vessel in this world. Submarines and targets. Skimmers are targets...

 

The displacement of the boats get smaller (lighter), so the water level in the lock goes down. One kg of iron iside the floating ship displaces one liter of water. The same kg of iron on the bottom of the lock displaces much less.

 

I really don't know? Does it have something to do with the fact that water cannot compress, but air can?


Oh, wait, it's the same phenomenon when freedivers suddenly gets negative buoyancy, right?

So, to take it from there, the (air) volume becomes much smaller because of the pressure, and when it does so, in order to keep the same amount of buoyancy, some of the weight has to go?

Am I close?

 

"Why does a submarine when it trims have to lighten itself more the deeper it goes? (neglecting temperature and related density issues)."

Maybe such a large structure displaces less the deeper it goes? (compression of even a steel structure) I imagine the internal air pressure of a submarine remains at surface
pressure, or near.

 

yes it's all about displacement, very simple concepts, very simple logic, just not intuitive.

Another classic for folks who know about electric motors and torque speed curves is why does a vacuum cleaner motor speed up if the pipe is blocked (as you load a series wound motor it's speed is supposed to go down).

 

Your lawyer gets a call from the other boater's insurer, who just got a call from his lawyer....

 

In danish we call it "sucking false air" ...

 

Stays the same. DISPLACEment is simply how much water that is displaced by a certain mass, who says that the ingots are heavierthan water?

 

Mikey,

Mass is different than weight.

Displacement includes more than weight, and iron ingots are usually not hollowed ;-)

 

No one said that the ingots were not hollow, they were to be used as floating mines by people posting in the Dealing with Pirates thread

Mikey

 

haha, true, that could be a possible use for such things.