Density of Submerged Objects in Water: Wood & Person

In summary, to find the density of a piece of wood that floats in water with 70% of its volume submerged, you need to set up an equation where the weight of the wood equals the weight of the water displaced. From there, you can rearrange the equation to find the density of the wood. Similarly, you can do the same process for a person floating in water with 5% of their volume above the surface, using the given percentage to find the density of the person.
  • #1
jerick232002
4
0
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?
 
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  • #2
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
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 I am going to do?first step?
 
  • #6
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
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?
 

1. What is density and how does it affect submerged objects in water?

Density is the measure of mass per unit volume. It is an important factor in determining whether an object will float or sink in water. Objects with a higher density than water will sink, while objects with a lower density will float.

2. How does the density of wood affect its ability to float in water?

Wood has a lower density than water, which is why it is able to float. The pores in wood contain air, which makes it less dense than water. This air also provides buoyancy, allowing the wood to float on the surface of the water.

3. Can a person float in water due to their density?

Yes, a person can float in water due to their density. The average density of the human body is slightly lower than that of water, which is why most people are able to float. However, this can vary depending on factors such as body composition and lung capacity.

4. What happens to the density of a person when they take a deep breath and submerge in water?

When a person takes a deep breath and submerges in water, their density decreases. This is because the air in their lungs increases their overall volume, making them less dense than the water around them. This allows them to float more easily.

5. How is the density of an object in water related to its weight and volume?

The density of an object in water is related to both its weight and volume. The weight of an object affects its density, as a heavier object will have a higher density. The volume of an object also plays a role, as a larger object will displace more water and have a lower density. This is why two objects of the same weight can have different densities in water.

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