Boyle's Law and Applied pressure

In summary, the conversation discusses the relationship between pressure and volume according to Boyle's Law. The pressure applied to the plunger of a Boyle's Law Apparatus can be calculated using P = F/A, and the change in pressure inside the cylinder can be calculated using P1V1 = P2V2. It is questioned whether the pressure applied to the top of the plunger should be equal to P2, and calculations show that they are not exactly equal. It is mentioned that atmospheric pressure and the weight of the plunger should be taken into account in calculations. Finally, it is confirmed that under constant temperature, P2 should equal the weight of the added mass plus atmospheric pressure.
  • #1
nmsurobert
288
36
When using a Boyle's Law Apparatus, pressure applied to the plunger can be calculated by knowing the mass of the object on the plunger and the area of the plunger. P = F/A.

The change of pressure inside the cylinder can be calculated using Boyles Law, P1V1 = P2V2

Should the value for the pressure applied to the top of the plunger be the same as P2, the pressure of the gas in the cylinder once the plunger has been compressed? should P2 = F/A ?

I did some math and math shows that they aren't equal. they're close, but not the same. however, i don't know if they should be equal under ideal conditions. using P = F/A, that value is slightly larger than using P2 = (P1V1)/V2
 
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  • #2
nmsurobert said:
Summary: P = F/A and Boyles Law relationship

When using a Boyle's Law Apparatus, pressure applied to the plunger can be calculated by knowing the mass of the object on the plunger and the area of the plunger. P = F/A.

The change of pressure inside the cylinder can be calculated using Boyles Law, P1V1 = P2V2

Should the value for the pressure applied to the top of the plunger be the same as P2, the pressure of the gas in the cylinder once the plunger has been compressed? should P2 = F/A ?

I did some math and math shows that they aren't equal. they're close, but not the same. however, i don't know if they should be equal under ideal conditions. using P = F/A, that value is slightly larger than using P2 = (P1V1)/V2
Neglecting the weight of the plunger, if the temperature is constant, the pressure P2 should equal the weight.
 
  • #3
Chestermiller said:
Neglecting the weight of the plunger, if the temperature is constant, the pressure P2 should equal the weight.

the weight? numerically, P2 = mg?
 
  • #4
nmsurobert said:
the weight? numerically, P2 = mg?
Plus the atmospheric pressure. In Boyle's law, one must use the absolute pressure.
 
  • #5
Chestermiller said:
Plus the atmospheric pressure. In Boyle's law, one must use the absolute pressure.

I'm taking atmospheric pressure into account. once a mass has been added to the top of the plunger,
P2 = F/A + 101325 N/m2 = (P1V1)/V2?
 
  • #6
nmsurobert said:
I'm taking atmospheric pressure into account. once a mass has been added to the top of the plunger,
P2 = F/A + 101325 N/m2 = (P1V1)/V2?
Yes, assuming the temperature is constant.
 
  • #7
Chestermiller said:
Yes, assuming the temperature is constant.
awesome. thank you!
 

1. What is Boyle's Law?

Boyle's Law is a gas law that states the relationship between the pressure and volume of a gas at a constant temperature. It states that as the pressure of a gas increases, its volume decreases and vice versa, as long as the temperature remains constant.

2. How is Boyle's Law applied in real life?

Boyle's Law is applied in various industries, such as scuba diving, where it is used to calculate the amount of air needed for a certain depth. It is also used in the production of compressed air, gas cylinders, and in the functioning of respiratory systems.

3. What is the formula for Boyle's Law?

The formula for Boyle's Law is P1V1 = P2V2, where P1 and V1 represent the initial pressure and volume, and P2 and V2 represent the final pressure and volume.

4. How does temperature affect Boyle's Law?

Boyle's Law only applies when the temperature remains constant. If the temperature changes, the relationship between pressure and volume will also change, and the law will no longer hold true.

5. What are some limitations of Boyle's Law?

Boyle's Law only applies to ideal gases, which do not exist in real life. It also assumes that the temperature remains constant, which is not always the case. Additionally, it does not take into account the effects of intermolecular forces or the size of gas particles.

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