Pressure in Liquids: How Does It Affect Volume?

In summary: Sorry, I don't understand what you are asking. Can you please clarify?Have you ever seen a diagram that shows how pressure and volume are related?No.
  • #1
Muhammad Danish
70
7

Homework Statement


upload_2018-4-16_18-13-3.png


Homework Equations


How does atmospheric pressure affects the volume of liquid? What will be the volume of the air bubble at the bottom of the lake?

The Attempt at a Solution


At the surface, the volume is 6.0cm3. So at the bottom, more pressure will be exerted so it will be halved to 3cm3. Please explain the concept, that was just a rough idea.

Thanks.
(regards)
 

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  • #2
The problem says, "Water of depth 10 m exerts a pressure equal to atmospheric pressure". Is this pressure an absolute pressure or a gauge pressure? In other words, if you had a lake that is 10 m deep, what would be the gauge pressure at the bottom of the lake? What would be the absolute pressure at the bottom?
 
  • #3
TSny said:
The problem says, "Water of depth 10 m exerts a pressure equal to atmospheric pressure". Is this pressure an absolute pressure or a gauge pressure? In other words, if you had a lake that is 10 m deep, what would be the gauge pressure at the bottom of the lake? What would be the absolute pressure at the bottom?
I am not familiar with the terms ''Gauge Pressure'' and ''Absolute Pressure''. Can you make it more simple..
 
  • #4
Gauge pressure is pressure measured relative to atmospheric pressure. Many pressure gauges measure gauge pressure (such as a gauge for measuring pressure in a tire). Absolute pressure is the "true" or "actual" pressure. A gauge pressure of 0 corresponds to an absolute pressure of 1 atmosphere. A gauge pressure of 0.5 atmospheres corresponds to an absolute pressure of 1.5 atmospheres.

The important thing in this problem is to know what the absolute pressure is at the top of the lake and also at the bottom of the lake.

If the lake is 20 m deep, what is the (absolute) pressure at the top of the lake? What is the (absolute) pressure at the bottom of the lake?
 
  • #5
TSny said:
Gauge pressure is pressure measured relative to atmospheric pressure. Many pressure gauges measure gauge pressure (such as a gauge for measuring pressure in a tire). Absolute pressure is the "true" or "actual" pressure. A gauge pressure of 0 corresponds to an absolute pressure of 1 atmosphere. A gauge pressure of 0.5 atmospheres corresponds to an absolute pressure of 1.5 atmospheres.

The important thing in this problem is to know what the absolute pressure is at the top of the lake and also at the bottom of the lake.

If the lake is 20 m deep, what is the (absolute) pressure at the top of the lake? What is the (absolute) pressure at the bottom of the lake?
Sorry, I do not understand..
 
  • #6
Forget the concept of gauge pressure. I didn't know that you are not familiar with it. It is not necessary for this problem.

You have to interpret carefully the meaning of the statement "Water at a depth of 10 m exerts a pressure of 1 atmosphere". This means that for every 10 m deeper that you go down in water, the pressure increases by 1 atmosphere.

If we have a lake of depth 20 m, can you answer the following?

(1) What is the pressure at the top of the lake?
(2) What is the pressure at a depth of 10 m in the lake?
(3) What is the pressure at a depth of 20 m (at the bottom of the lake)?
 
  • #7
TSny said:
Forget the concept of gauge pressure. I didn't know that you are not familiar with it. It is not necessary for this problem.

You have to interpret carefully the meaning of the statement "Water at a depth of 10 m exerts a pressure of 1 atmosphere". This means that for every 10 m deeper that you go down in water, the pressure increases by 1 atmosphere.

If we have a lake of depth 20 m, can you answer the following?

(1) What is the pressure at the top of the lake?
(2) What is the pressure at a depth of 10 m in the lake?
(3) What is the pressure at a depth of 20 m (at the bottom of the lake)?
1) 0 atmosphere
2) 1 atmosphere
3) 2 atmospheres
Am I right?
 
  • #8
Muhammad Danish said:
1) 0 atmosphere
2) 1 atmosphere
3) 2 atmospheres
Am I right?
No. You have forgotten that the surface of the lake is exposed to the atmosphere. So, the pressure at the surface is not 0.
 
  • #9
TSny said:
No. You have forgotten that the surface of the lake is exposed to the atmosphere. So, the pressure at the surface is not 0.
It should be 1 too?
 
  • #10
Muhammad Danish said:
It should be 1 too?
Right. So, what are the answers to the three questions of post #8?
 
  • #11
TSny said:
Right. So, what are the answers to the three questions of post #8?
1) 1 atmosphere
2) 2 atmospheres
3) 3 atmospheres
 
  • #12
Muhammad Danish said:
1) 1 atmosphere
2) 2 atmospheres
3) 3 atmospheres
Yes.
 
  • #13
TSny said:
Yes.
Alright, Now how will we connect these pressures with volumes?
 
  • #14
Have you studied the ideal gas law?
 
  • #15
use Boyle's law : P1V1 = P2V2
 
  • #16
TSny said:
Have you studied the ideal gas law?
I have studied P1V1 = P2V2
 
  • #17
Muhammad Danish said:
I have studied P1V1 = P2V2
OK. That's a special case of the ideal gas law when the temperatures in states 1 and 2 are the same. The equation P1V1 = P2V2 is called "Boyle's law" as mentioned by @patric44

Can you use Boyle's law to get the answer?
 
  • #18
TSny said:
OK. That's a special case of the ideal gas law when the temperatures in states 1 and 2 are the same. The equation P1V1 = P2V2 is called "Boyle's law" as mentioned by @patric44
By using the Boyle's Law, the answer is 2 cm3. Is it correct?
 
  • #19
Muhammad Danish said:
By using the Boyle's Law, the answer is 2 cm3. Is it correct?
Yes.
 
  • #20
TSny said:
Yes.
Thanks a lot for helping me!
 
  • #21
patric44 said:
use Boyle's law : P1V1 = P2V2
Thanks.
 

Related to Pressure in Liquids: How Does It Affect Volume?

1. How does pressure affect the volume of liquids?

Pressure and volume have an inverse relationship in liquids. This means that as pressure increases, the volume of the liquid decreases and vice versa. This is known as Boyle's Law.

2. How does pressure affect the density of liquids?

As pressure increases, the density of liquids also increases. This is because the increased pressure causes the molecules to be more tightly packed together, resulting in a higher density.

3. How is pressure measured in liquids?

Pressure in liquids is commonly measured in units of Pascal (Pa) or pounds per square inch (psi). In scientific experiments, a device called a manometer is often used to measure pressure.

4. How does pressure in liquids differ from pressure in gases?

Unlike gases, liquids are relatively incompressible, meaning that their volume does not change significantly with changes in pressure. This is due to the strong intermolecular forces between liquid molecules.

5. How does pressure affect the boiling point of liquids?

As pressure increases, the boiling point of liquids also increases. This is because the increased pressure makes it more difficult for the liquid molecules to escape into the gas phase, requiring a higher temperature to reach the boiling point.

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