Buoyancy Force

[flyguy56]

I'm stuck with how to find the buoyancy force on an object.

 

I know how to find density but I can't find it in my textbook how to find the buoyancy force.

 

 

Could someone help with the general idea of finding the buoyancy force? I don't need the answer, just what equation I should be using for this.

 

Thanks.

[insane_alien]

there are two ways of doing this

 

1/ you can do a differential force balance by considering the geometry of the object and the respective depths(this is only practical for simple shapes as it can get very complicated very quickly)

 

2/ you work out the mass of water displaced by the object. the weight of this displaced water will be equal to the buoyancy force.

[flyguy56]

Okay, didn't understand the first one, so for the second one.

 

If the mass of the object is 180 kg - then the weight is f = mg or f = 180 kg * 9.8m/s^2 = 17287.2 N.

 

Is that correct? I'm so lost.

[swansont]

How much volume does the object displace? (You can get this from the mass and density)

 

The weight of water of that volume is the buoyant force.

[Bignose]

flyguy,

 

for the second choice, look up "Archimedes' Principle" in your favorite Internet search Engine

[flyguy56]

Thanks for the help everyone.

 

So F = dvg.

 

Thanks for all the help. See ya around.