Does someone weigh more on a steel ship?

[Johann1234]

Say you were on a steel ship, standing on very thick steel. Would you technically weigh more? Would the gravity pull you down more?

 

[jambaugh]

Since the ship is floating one can presume it is actually less dense overall than the water it displaces (since it floats partly above water) and thus there is actually less mass immediately below you than would be if you were standing on the ground (which is denser than the water). So you should actually be a wee bit lighter.

 

[sophiecentaur]

Gravitational Anomalies are detectable all over the place, where there is a particularly massive object in the vicinity. Mountains, containing a lot of dense materials will deflect a plumb bob significantly. But I think you'd find it hard, in practice, to detect a change of local g unless the object in question was a good few thousand tonnes and quite close, although, G has been measured using very large lumps of metal and a torsion balance. (http://www.physics.arizona.edu/~haar/ADV_LAB/BIG_G.pdf)

 

[OmCheeto]

Since the ship is floating one can presume it is actually less dense overall than the water it displaces (since it floats partly above water) and thus there is actually less mass immediately below you than would be if you were standing on the ground (which is denser than the water). So you should actually be a wee bit lighter.

But what if their center of mass was below sea level? I would imagine a person sitting in a 1 meter thick shelled steel pumpkin without an upper deck would be below the water line.

ps. I'm afraid the maths involved in this problem look as though they are beyond my capabilities, so I'll not be helping solve this problem.

I would suggest though using the "Homework" template:

Homework Statement

Homework Equations

The Attempt at a Solution

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pps. Looks like she's using duct tape to hold it together. Good for her!

 

[Vanadium 50]

But what if their center of mass was below sea level?

Then you would also be lighter (for a constant Earth density) because the mass above you does not contribute the gravitational pull. The fact that water is much less dense than the Earth means that the fact you are closer to the Earth is more important and you're a wee bit heavier.