Homework Help: Stainless Steel in Sea Water

You should be able to use Archimedes principle. The buoyant force is equal to the weight of fluid displaced by the object. Calculate the weight of the volume of equivalen seawater and subtract that off I believe.

 

Yeah, that's how I would work it. We'll see if anyone here ends up disagreeing.

 

Does one mean 13 (13.000) kg, or perhaps 13,000 g? kg (g) is a unit of mass, N (Newton) or dyne (used in cgs system) is a measure of weight. Mass * acceleration of gravity would give weight (force) due to gravity.

The apparent mass in seawater would be 11.309 kg (11,309 g). The application of Archimedes principle (buoyancy) is correct.

In English units, one will find pounds mass (lbm) and pounds force (lbf), but strictly speaking they are not the same.

 

He doesn't like your use of kilograms as a unit of weight. Technically, kilogram is a unit of mass, Newtons would be an appropriate unit of weight.

 

As Born2bwire indicated, I was referring to the use of mass as weight. Being a physics forum, we wish to be accurate in such a matter.

I agree with the calculation that 13 kg of steel as described would have the weight equivalent of 11.3 kg (as measured in air), when the steel is immersed in seawater of density (1025 kg/m³), i.e. it appears lighter in water than it would in air.