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Volume Submerged

  • #1
1.) What is the density of a piece of wood that floats in water with 70% of its volume submerged?

2.) calculate the density of a person who floats in water with 5% of her volume above the surface?
 

Answers and Replies

  • #2
2,685
20
I assume this is a school work question and so you're going to have to show some working before we can help.
 
  • #3
i don't know how. i think first to do is to look for the value of mass? and then?please help me..
 
  • #4
2,685
20
Well the questions aren't about finding an exact solution, you need to rearrange the equations, inserting any known values and then you will come out with a ratio.
 
  • #5
the exact solution is d=m/v?right? but the only given is the percent, volume?what im going to do?first step?
 
  • #6
2,685
20
Density = Mass / Volume

For an object to float, it has to displace an amount of water equal to it's weight. In this case, when 70% of the wood is submerged, that amount of water equals the weight of the wood.

So how can you put all of this together with equations and come up with a way of expressing the volume?
 
  • #7
Mass = 1000 g /Volume??
 
  • #8
2,685
20
When weight of object = weight of water displaced the object floats.

Weight of object = mg = weight of water displaced = mg

Density = Mass / Volume

Mass = Density x Volume

Weight of object = DwoodVwoodg

Weight of water displaced = Dwater0.7Vwoodg

So you get:

DwoodVwoodg = Dwater0.7Vwoodg

You can take out gravity:

DwoodVwood = Dwater0.7Vwood

You can also cancel out Vwood:

Dwood = 0.7Dwater

D = Density, V = Volume, g = gravity

Can you follow this?
 

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