Anchor lifting bouys

[Barry]

I suppose it's the surrounding fluid and depth that supports the object,so,if I weighed a fish at 1 att,
you are saying it would weigh the same as it does out of the water?
I suppose bouyancy comes into the equation somewhere.ie,there is no bouyancy in a lead ball.

It will not make a lot of difference as to how far that you immerse the object in water. A bit, but negligible as liquids are virtually incompressible. (ie the density of what the object is in changes the buoyant force)

Lead has buoyancy but not enough to float it if solid

A cubic foot of lead weighs 708 pounds in air, on earth at sea level

Immerse it say 2 feet, and it weighs 708 minus 64 pounds per cubic foot in sea water or 644 pounds

 

[TANSL]

What is the weight of 60 kg in space??

Are you talking about 60 kg-weight or 60 kg-mass?
You probably know that the weight of an object on Earth depends on the force of Earth's gravity. When you speak of the weight of an object in space, what force of gravity is that which acts upon it? There you have your answer, think a little.

 

[Barry]

Are you talking about 60 kg-weight or 60 kg-mass?
.

There is not kilogram weight in space. That is the point. One kilogram mass does not weigh one kilogram in space

I am not looking for an answer, just trying to get you to accept the fact that when you immerse something that weighs 15 kg above water, it does not weigh 15 kg when it is under water.

 

[TANSL]

Barry, I agree with you about space. Otherwise, I think, you're wrong. Although it could be just a way of expressing itself, a semantic question.
On the surface of the Earth, a kilo mass weighs a kilo force and, as long as it does not change the mass, the Earth will attract it with the same force, that is, it will always weigh the same. In another environment, not terrestrial, with another gravitational force (in the moon, for example), a kilo mass does not weigh a kilo force. If you do not change the mass and do not change the acceleration of gravity, the weight does not change.
The apparent weight, I repeat for the third time, is something else, which depends not on the weight of the object but on the fluid in which it is submerged.
From Wikipedia : "The kilogram-force (kgf or kgF), or kilopond (kp, from Latin pondus meaning weight), is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a 9.80665 m/s2 gravitational field (standard gravity, a conventional value approximating the average magnitude of gravity on Earth)".
I suppose all this does not care much to the OP so I finish my intervention on the matter of mass and weight.
A pleasure to talk to you.

 

[valvebounce]

so,if I immerse a 25kg drum to one atmosphere,(7.14 lbs) would the upward force increase or decrease?

 

[Barry]

so,if I immerse a 25kg drum to one atmosphere,(7.14 lbs) would the upward force increase or decrease?

Not sure exactly what you mean by immersing a drum to one atmosphere. (which is 14.7 psi)

Any time you immerse anything into water there is an upwards force acting on the object equal to the weight of the water that the object displaces.

Once an item is fully immersed, the upward force due to buoyancy is maxxed no matter to what depth the object is immersed to.

(qualifier, there is a slightly higher density with increasing depth, so a slightly higher upward buoyant force. I believe that the highest change in density of water is about 4% at miles below the surface of the water.

 

[baeckmo]

Yes, that's correct.
And forgive me if I insist, the weight of the object does not change.

Wrong; the MASS is constant, but its WEIGHT is varying with gravitation level, and its APPARENT WEIGHT is related to the fluid it is submerged in!

 

[TANSL]

Baeckmo, well look, I'm convinced I'm saying exactly the same as you. Please review all my posts. So yes, I agree with you.

 

[Sparky568]

If the OP is still tuned in you could just buy one of these.


https://www.westmarine.com/buy/iron...&creative=73942171623915&device=c&matchtype=e


Thanks for the physics lesson though.

 

[valvebounce]

If the OP is still tuned in you could just buy one of these.


https://www.westmarine.com/buy/iron...&creative=73942171623915&device=c&matchtype=e


Thanks for the physics lesson though.

Haha,I had a physics lesson too.

$70 is a lot more than it would cost me to make one up,I could make it for £11.($)?

,

 

[valvebounce]

Not sure exactly what you mean by immersing a drum to one atmosphere. (which is 14.7 psi)

Any time you immerse anything into water there is an upwards force acting on the object equal to the weight of the water that the object displaces.

Once an item is fully immersed, the upward force due to buoyancy is maxxed no matter to what depth the object is immersed to.

(qualifier, there is a slightly higher density with increasing depth, so a slightly higher upward buoyant force. I believe that the highest change in density of water is about 4% at miles below the surface of the water.[/QUOTE

One att= about 5ft deep.So you have answered my question,no matter what the depth
once fully immersed the upward force stays the same.
With an increase in depth the water pressure increases about 7.14 lb
with each atmosphere

 

[Barry]

One att= about 5ft deep.So you have answered my question,no matter what the depth
once fully immersed the upward force stays the same.
With an increase in depth the water pressure increases about 7.14 lb
with each atmosphere[/QUOTE]


Your numbers are off

At sea level, atmospheric pressure is 14.7 psia the "a" stands for absolute, ie compared to a total vacuum.

Normally a gauge would read 0 at sea level. (subject to temp) Because most pressure gauges read 0 at sea level, the proper designation is 0 psig, which stands for psi guage.

In order to add another atmosphere of pressure to make the gauge read 14.7 psig, you need to reach a depth of about 33 feet.

Not 5 as you suggested.

 

[valvebounce]

I'd certainly forgotten my maths Barry,it's a while since I used them I must admit,at 72 I suppose I can blame it on age.
I think every 5ft was the depth average that I had to pinch my nose to equalise pressure in my eustachion tubes when I did a bit of sub aqua diving years ago.
Just cant stay away from the water,probably got the bug from my Dad,he was a CPO in the Royal Navy
in WW2.

 

[gonzo]

The traditional definition of "weight" in Newtonian physics and engineering is the downwards force of an object which can be measured with a scale. In modern physics, weight is also defined as the force exerted on an object by gravity. However, that gets changed by relativity, where the velocity also affects the mass and weight. For our purposes, the first definition is appropriate.

 

[Sparky568]

You guys watch too much big bang theory.