# Buoyancy question

1. Dec 4, 2007

### kaweezah

Is it be possible for the buoyancy force be greater than the object's mass? when can it be?

2. Dec 4, 2007

### cristo

Staff Emeritus
This sounds like homework. Do you have any thoughts? Further, I don't think you mean "mass" since one cannot compare objects with different dimensions.

3. Dec 4, 2007

### pixel01

Think about boats, ships etc.. they all float !

4. Dec 4, 2007

### kaweezah

hey cristo.....i meant WEIGHT...

5. Dec 4, 2007

6. Dec 4, 2007

### wysard

Of course. Whenever the volume of the object in question displaces more mass of the substance it is immersed in than it's own mass.

Edit: Whoops. Sorry stewartcs, yep that link just about sums it up!

7. Dec 4, 2007

### noagname

as far as i know
well in the big boats they keep some type of air at the bottom of the boat so that there is more bouncy so in other words i think so

8. Dec 4, 2007

### Staff: Mentor

The potential buoyancy of an object is completely unrelated to its weight. The actual buoyant force on an object that is floating is exactly equal to its weight. The buoyant force on a submerged object depends on its volume and the weight density of the fluid only.

9. Dec 4, 2007

### Staff: Mentor

As a matter of fact, at the very bottom of big boats is where the heaviest equipment and fuel are kept, for stability. Otherwise, anywhere below the water line of a boat, where there is nothing but air (ie, in the middle of a corridor or room), that air is where water could have been, so it contributes to buoyancy.

10. Dec 4, 2007

### noagname

ok so i am taking it that i am half right and half wrong
just like a glass of water

11. Dec 6, 2007

### kaweezah

I asked this question because I've read sources always stopping if their weights are EQUAL..never saying if the boat was lighter that it could still be possible then....why is it that those sources never mention the lighter thing/part...

12. Dec 6, 2007

### Staff: Mentor

Because boats don't get pulled down - In order to submerge an object that has enough buoyancy to float, you have to use another force to force it underwater.

13. Dec 6, 2007

### arildno

You can raise shipwrecks from the sea-bottom by attaching inflatable balloons, or floaters to them.

The point about doing this is to increase the volume of displaced water, so that the ship+balloon system will experience a buoyancy force greater than its weight.