- #1
Hippoman
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Ok, so I've a couple of assignments that require the understanding of the basic principles of buoyancy and displacement of a ship and I'm a bit confused.
Consider a ship that has a displacement of 7 000 000 kg. That's the mass of the water that the ships displacement "pushes out" from its way, right? So why is it generally stated that displacement = mass of the ship (for example Wikipedia states this)?
If the buoyancy force acting on the ship = water density * g * displacement volume.
Now if we solve for the volume, we have a displacement volume (water density 1000kg/m3)
of 7000m3. Now, if we assume that the ship and the displacement are "fully wooden", so no empty spaces, the mass is 7000m3 * wood density, say 700kg/m3, = 4 900 000kg. So what's wrong here?
Generally speaking, is the displacement of a ship always the same? I mean, it cannot always be just the same amount of water that it's displacing because the ship has to go up an down from time to time. Why are the size of the ships demonstrated by the displacement if this is the case?
The other thing about the buoyancy: if we have an object laying at the bottom of the sea, is there a buoyancy force acting on it? I can't find any clear statement about this.
I realize that these should be easy subjects but I'm quite poor with physics so don't be too rough on me :)
Consider a ship that has a displacement of 7 000 000 kg. That's the mass of the water that the ships displacement "pushes out" from its way, right? So why is it generally stated that displacement = mass of the ship (for example Wikipedia states this)?
If the buoyancy force acting on the ship = water density * g * displacement volume.
Now if we solve for the volume, we have a displacement volume (water density 1000kg/m3)
of 7000m3. Now, if we assume that the ship and the displacement are "fully wooden", so no empty spaces, the mass is 7000m3 * wood density, say 700kg/m3, = 4 900 000kg. So what's wrong here?
Generally speaking, is the displacement of a ship always the same? I mean, it cannot always be just the same amount of water that it's displacing because the ship has to go up an down from time to time. Why are the size of the ships demonstrated by the displacement if this is the case?
The other thing about the buoyancy: if we have an object laying at the bottom of the sea, is there a buoyancy force acting on it? I can't find any clear statement about this.
I realize that these should be easy subjects but I'm quite poor with physics so don't be too rough on me :)