Fluid mechanics of floating wood

In summary, when more air is pushed into the bottle from the pump, the air pressure inside the bottle increases. This affects the floatation of the piece of wood, which will have the same part submerged in the water. This is because according to Archimedes' principle, the liquid exerts a force (upwards) on the immersed object equal to the weight of the displaced fluid. When an object is floating at rest, this force is equal to its own weight. Since the mass of the wood will not change, the increased air pressure will not affect its floatation.
  • #1
utkarshakash
Gold Member
854
13

Homework Statement


A piece of wood is floating in water kept in a bottle. The bottle is connected to an air pump. Neglect the compressibility of water. When more air is pushed into the bottle from the pump, the piece of wood will float with

a)larger part in the water
b)lesser part in the water
c)same part in the water
d)it will sink

Homework Equations



The Attempt at a Solution


When more air is pushed the air pressure inside the bottle increases. But what will be its effect on floatation?
 
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  • #2
I'm not sure it's possible to answer this exactly without more knowledge of how wood responds to changes in air pressure. But I think they're trying to get you to consider what determines the volume of the block that's submerged. Can you state Archimedes' principle?
 
  • #3
haruspex said:
I'm not sure it's possible to answer this exactly without more knowledge of how wood responds to changes in air pressure. But I think they're trying to get you to consider what determines the volume of the block that's submerged. Can you state Archimedes' principle?

The liquid exerts a pressure on the solid immersed which is equal to the weight of the displaced fluid.
 
  • #4
utkarshakash said:
The liquid exerts a pressure on the solid immersed which is equal to the weight of the displaced fluid.
Shouldn't say pressure there. It exerts that force (upwards). Pressure is force per unit area.
When an object is floating, at rest, what force would that be equal to?
 
  • #5
haruspex said:
Shouldn't say pressure there. It exerts that force (upwards). Pressure is force per unit area.
When an object is floating, at rest, what force would that be equal to?

Weight of the displaced fluid which is equal to (Density of liq.*vol of solid immersed*g)
 
  • #6
utkarshakash said:
Weight of the displaced fluid which is equal to (Density of liq.*vol of solid immersed*g)
True, but what I meant was, what other force is it equal to?
 
  • #7
haruspex said:
True, but what I meant was, what other force is it equal to?

Its own weight.(Mass*g)
 
  • #8
Right. Now, what will the increased air pressure do to the mass and volume of the wood?
 
  • #9
haruspex said:
Right. Now, what will the increased air pressure do to the mass and volume of the wood?

Nothing:biggrin:
 
  • #10
utkarshakash said:
Nothing:biggrin:
Well, it won't change the mass, but it might squeeze it a bit.
 

FAQ: Fluid mechanics of floating wood

1. What is the role of fluid mechanics in understanding floating wood?

Fluid mechanics is the branch of physics that studies the behavior of fluids (liquids and gases) in motion. When it comes to floating wood, fluid mechanics helps us understand the forces acting on the wood and how it interacts with the surrounding fluid.

2. How does the shape of the wood affect its floating behavior?

The shape of the wood plays a crucial role in its floating behavior. The shape determines the amount of water displaced by the wood and consequently, the buoyant force acting on it. A larger displaced volume of water results in a greater buoyant force and higher floating ability.

3. What is the significance of the density of floating wood?

The density of floating wood is significant because it determines whether the wood will float or sink. Wood with a lower density than water will float, while wood with a higher density will sink. The density of wood also affects its stability and ability to remain afloat.

4. How do external factors like waves and currents impact the floating behavior of wood?

External factors such as waves and currents can affect the floating behavior of wood in several ways. Waves can create additional forces on the wood, causing it to move or even capsize. Currents can also affect the stability of the wood, as they can push it in different directions and change the balance of forces acting on it.

5. Can fluid mechanics principles be applied to other floating objects besides wood?

Yes, fluid mechanics principles can be applied to other floating objects such as boats, ships, and even icebergs. The same concepts of buoyancy, density, and external forces apply to all floating objects and are crucial in understanding their behavior in different fluid environments.

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