Another Physics Brain Teaser

[stonebreaker]

A ton of feathers or a ton of lead... so near, and yet so far...

 

[Man Overboard]

stay the same, its that same as taking a pee in the bath tub the water level will stay the same,, and before you say something iam a showerman

Actually, the water level in this situation would go up, unless you were floating in the tub at the time you peed.

 

[Man Overboard]

What happens to the water level relative to the lock sides?

Some folks need to read more carefully and reconsider. The water level will change if there is a change in displacement; now then, is there a change in displacement?

 

[Poida]

Well Tom, that would depend on what Jack was drinking before he peed. If he was floating in the water, peed, and his pee had less density than the bath water then due to the less density Jack would sink displacing more water thus making the water level rise. And, the opposite would occur if his urine was denser than the bath water.

I will do a google on the specific gravity of urine. We've got to get to the bottom of this. Oops.

 

[Poida]

Have to correct myself as I have just googled urine and specific gravity and it doesn't matter what you drink as urine in a healthy person is between 1.002 and 1.028. The water level will fall as Jack's hull will be pushed up thus taking up less volume and the water in the bath will fall.

However a medical problem can change the specific gravity of urine, not a mental problem. Jack has already stated he does not pee in the bath as he showers. Peeing in the shower, quite normal??

Bouyancy could change if Jack's skeg gets caught in the plug hole.

 

[Man Overboard]

Poida,
remember, we are talking about the level on the side of the Lock, or tub in this case, so if the pee sinks to the bottom of the tub, the net change in volume stays the same, if the pee floats, again the net change in volume remains unchanged. Jack on the other hand will float ever so slightly higher, as he now has less mass.

 

[rayk]

Everyone is giving reasons, so I will too

While the ingots are in the hull, they displace their weight, as a volume of water.
When the ingots are tossed into the lock, they displace their physical volume.

A 64lb ingot displaces one cubic foot of seawater on the ship.
But in the lock the 64lb ingot displaces far less than one cubic foot of water.

Toss the first ingot into the air and the ship displaces 64lb less. The water level drops as the ship rises. When the ingot hits the water the water level rises again, but by less than the initial level.

A steel ship loaded with iron ingots and continuously fully borne on water is moved into a lock and the gates of the lock are closed. No water can come in or go out of the lock.
The crew takes all the iron ingots and throws them into the water in the lock.
What happens to the water level relative to the lock sides?

 

[Man Overboard]

Rayk, you are always thinking; first the anchor drum thing and now this!! You are on a roll. I'll go with Rayk's answer.

 

[DGreenwood]

Of course rayk is correct.
If you think about why an iron ingot sinks, then you understand why it will displace more and float while it is in a ship.

The level does go down relative to the lock sides.

 

[westlawn5554X]

great, no salt water was mentioned... it could have been a steel vessel in a river.

 

[DanishBagger]

Certainly goes down. Rayk must be right.

- Thanks for these brain teasers!! I like them!

 

[timgoz]

I thought down for the same reason. To verify I took a large & small plastic cup, and a pocket full of coins and experimented.

TGoz

 

[DanishBagger]

That's cheating, Tim!

It was supposed to be a brain teaser, not a practical experiment ;-)

 

[Man Overboard]

I like Rayk's saying at the end of his posts, I think it applies here!

Well it works in practice... but will it work in theory..?

 

[fiberglass jack]

Tgoz was that you that i saw panhandling out side the mall