Boyle's Law and Applied pressure

Click For Summary

Discussion Overview

This discussion revolves around the application of Boyle's Law in a Boyle's Law Apparatus, specifically examining the relationship between the pressure applied to a plunger and the pressure of the gas in the cylinder. Participants explore the calculations involved in determining pressure using the formulas P = F/A and P1V1 = P2V2, while considering factors such as atmospheric pressure and the weight of the plunger.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Some participants propose that the pressure applied to the plunger, calculated using P = F/A, should equal P2, the pressure of the gas in the cylinder after compression.
  • Others argue that their calculations show P and P2 are close but not equal, raising questions about whether they should be equal under ideal conditions.
  • One participant suggests that neglecting the weight of the plunger and assuming constant temperature, P2 should equal the weight (P2 = mg).
  • Another participant adds that atmospheric pressure must be considered, indicating that Boyle's Law requires the use of absolute pressure.
  • There is a discussion about incorporating atmospheric pressure into the calculations, with a participant stating P2 = F/A + atmospheric pressure.
  • Some participants confirm that the assumptions made (like constant temperature) are valid for their calculations.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the equality of P and P2, with no consensus reached on whether they should be equal under ideal conditions. There are competing views on how to incorporate atmospheric pressure into the calculations.

Contextual Notes

Participants mention the need to account for atmospheric pressure and the weight of the plunger, indicating that assumptions about these factors may affect the calculations. The discussion does not resolve the implications of these assumptions on the relationship between P and P2.

nmsurobert
Messages
288
Reaction score
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
 
Physics news on Phys.org
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.
 
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?
 
nmsurobert said:
the weight? numerically, P2 = mg?
Plus the atmospheric pressure. In Boyle's law, one must use the absolute pressure.
 
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?
 
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.
 
Chestermiller said:
Yes, assuming the temperature is constant.
awesome. thank you!
 

Similar threads

Graduate Calculate Flow Rate of a Syringe: Poiseuille's & Bernoulli's Laws
  • · Replies 5 ·
Replies
5
Views
17K
High School Confused about Boyle's Law, Charles' Law and the pressure Law?
  • · Replies 5 ·
Replies
5
Views
2K
Zeroth Law of Thermodynamics
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Pressure vessel exploding within an atmospheric chamber
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Calculate the work done by pressure rupturing a spherical containment
  • · Replies 7 ·
Replies
7
Views
2K
Graduate Can a Self-Gravitating Gas Ball Simulate Stellar Formation Dynamics?
  • · Replies 5 ·
Replies
5
Views
2K
How to calculate the leak rate based on pressure drop
  • · Replies 4 ·
Replies
4
Views
6K
High School How does liquid starts moving when there is Pascal's law
  • · Replies 15 ·
Replies
15
Views
2K
Effect on Volume of a Change in the Pressure of Compressible Gas
  • · Replies 2 ·
Replies
2
Views
1K
Graduate Equation for spring force for a cylinder on compressed air
  • · Replies 1 ·
Replies
1
Views
4K