How much does my 40Kg anchor weigh when in sea water?

[Bouba]

Dude, you really need to learn some basic physics - think of old-fashioned, spring scales - no seals, just a flat plate attached to a spring and a dial that moves if a weight is applied.

Now put those scales in water of any depth. They will read zero, because the water under the plate is pushing up as hard as the water over the plate is pushing down. There is no force to move the plate.

None of the parts have magically become heavier either - they are the same parts, consisting of the same number of atoms.

Yes...if you don’t waterproof the pressure plate. But waterproofing something that you put underwater is not unreasonable

 

[KevinV]

Yes...if you don’t waterproof the pressure plate. But waterproofing something that you put underwater is not unreasonable

Okay, I've tried really hard, I give up.

 

[PeterV]

It isn’t the mass of a submarine that decreases with depth but the buoyancy. Far more so with a modern fully tiled submarine and even more when compressible flank arrays are fitted.

 

[Bouba]

Okay, I've tried really hard, I give up.

It’s weight we are measuring not mass...if I put on a top hat full of water, I will weigh more

 

[capnsensible]

It isn’t the mass of a submarine that decreases with depth but the buoyancy. Far more so with a modern fully tiled submarine and even more when compressible flank arrays are fitted.

See #57.

The change in mass is compensated with internal ballast tanks.

When returning to periscope depth in the dark.....control room in black lighting for the Captain to see out of the periscope ....and one also has to compensate for the slop drain, sewage and brine tanks being emptied in a high sea state, the opportunity to get moaned at is high.

A few extra revs can help.

 

[KevinV]

It’s weight we are measuring not mass...if I put on a top hat full of water, I will weigh more

Because you've added mass

 

[mjcoon]

It’s weight we are measuring not mass...if I put on a top hat full of water, I will weigh more

Perhaps you could study how a U-tube (the original one, not the new spelling) works. It shows how water pressure works in all directions, not just downwards. Hydrostatics.

 

[Rappey]

Im struggling to use this-
Immersed Weight Calculator

A 40 lb anchor would weight 34.8lb in sea water ?
Steel is about 13% lighter immersed.
Concrete is around 43% lighter.
Maybe someone can figure out how to use the calculator and see if im right

 

[Bouba]

Perhaps you could study how a U-tube (the original one, not the new spelling) works. It shows how water pressure works in all directions, not just downwards. Hydrostatics.

I’ve assumed that the anchor is on the sea floor

 

[mjcoon]

I’ve assumed that the anchor is on the sea floor

The science of hydrostatics is the same on the seafloor and in your kitchen; just the numbers are different. I don't understand your comment...

 

[Bouba]

The science of hydrostatics is the same on the seafloor and in your kitchen; just the numbers are different. I don't understand your comment...

Everywhere there is a balance of forces...a Newtonian thing...so, I stand on the floor and the floor pushes upwards with an equal force..or I would go through the floor or shoot up through the roof...but I still weight something, I still have a gravitational force affecting me and that is my body weight...if I stood on the ocean floor I still have a gravitational attraction to the center of the earth..I still weigh something...and water weights something due to gravity...even if there is an equal and opposite FORCE from the sea bed

 

[KevinV]

The science of hydrostatics is the same on the seafloor and in your kitchen; just the numbers are different. I don't understand your comment...

Don't go there if you value your sanity - it's all to do with anchor shaped scales and wearing top hats full of water in some parallel universe where physics works differently from this one.

 

[Bouba]

Don't go there if you value your sanity - it's all to do with anchor shaped scales and wearing top hats full of water in some parallel universe where physics works differently from this one.

I’ll have one more go at this...then retire to a monastery and chant....there are a billion tons of water in the sea (I just made up that figure)...and the sea floor pushes up with an equal force...otherwise the water would crash through the sea bed...in fact the sea floor pushes up slightly more because some thoughtless boater, who doesn’t give a toss about Issac Newton, just dropped a forty kilo anchor on the sea floor. But even though there is equilibrium in the forces (equal from all directions)...there still is a billion tons of water...that is a weight...a billion tons going downward towards the earths core in the direction of gravity...and on that sea floor there is also an anchor...and its forty kilos are also going downwards due to gravity...and above that anchor is water...not the whole billion tons worth..just a slither of it. The original question was about weight...not mass..not pressure..not other non gravitational forces

 

[mjcoon]

Don't go there if you value your sanity - it's all to do with anchor shaped scales and wearing top hats full of water in some parallel universe where physics works differently from this one.

It's about time we had a bit of a relevant tangent...

Years ago Dragon's Den had an item on a floatation device for water-goers. It was a keyring with an inflatable float cited as capable to lift a kilogram. But from what depth was not specified. But since the gas would take a short while to be evolved (I don't think it was as fast as a LJ CO2 cartridge) if the float got too deep the gas would be compressed and would provide less buoyancy. This was not, of course, mentioned...

 

[Bouba]

It's about time we had a bit of a relevant tangent...

Years ago Dragon's Den had an item on a floatation device for water-goers. It was a keyring with an inflatable float cited as cable to lift a kilogram. But from what depth was not specified. But since the gas would take a short while to be evolved (I don't think it was as fast as a LJ CO2 cartridge) if the float got too deep the gas would be compressed and would provide less buoyancy. This was not, of course, mentioned...

That would be pretty bad if it happened to your self inflating life jacket

 

[KevinV]

in fact the sea floor pushes up slightly more because some thoughtless boater, who doesn’t give a toss about Issac Newton, just dropped a forty kilo anchor on the sea floor.

No, the anchor was already being carried by a boat displacing it's weight, already being supported by the sea bed. There isn't more weight in total on the seabed whether it's in the boat, up the mast, hanging off the bow, or on the seabed

 

[Bouba]

No, the anchor was already being carried by a boat displacing it's weight, already being supported by the sea bed. There isn't more weight in total on the seabed whether it's in the boat, up the mast, hanging off the bow, or on the seabed

You got me on that one

 

[Bouba]

No, the anchor was already being carried by a boat displacing it's weight, already being supported by the sea bed. There isn't more weight in total on the seabed whether it's in the boat, up the mast, hanging off the bow, or on the seabed

If you climbed up a mountain with your anchor weighed it, then dropped it over the side and someone weighed it again it would be different because of the distance from the earths center....the air pressure would be different but negligible...but water is not negligible...it’s heavy

 

[Momac]

Everywhere there is a balance of forces...a Newtonian thing

True.
But you are confusing weight and pressure
What you consider to be weight is a vertical force due to gravity
Vertical force = mass x the acceleration due to gravity . This force is measured in Newtons. (You have already stated you are in agreement with Newtons laws is I hope you don't mind if I use the unit of force named after Newton ).

Above water level do you think your weight includes the column of air above your head? It does not. But your body experiences the pressure from the air which is equal in all directions.
So , similarly, in water your weight (the vertical downward force due to gravity) has no connection with the weight of water.
However you can just float in water as long as you have air in your lungs due to buoyancy .
But an object that is more dense than water will sink.

 

[st599]

Nothing can weigh 40kg. The kg is the SI unit of mass. The SI unit of weight is the Newton.