Simple Fluid mechanics question, Need Help

Click For Summary

Discussion Overview

The discussion revolves around the calculation of forces exerted by water on a vertical wall in fluid mechanics, specifically addressing two different approaches to solving similar problems. Participants explore the concepts of gauge pressure versus absolute pressure and how they relate to the total force versus the force exerted by water alone.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that two problems regarding the force on a vertical wall were solved differently, with one approach incorporating atmospheric pressure and the other not.
  • Another participant suggests that the difference in solutions may stem from one problem asking for the total force while the other asked for the force done by water, indicating a potential distinction in the problem statements.
  • A later reply confirms the distinction between total force and force done by water, but expresses uncertainty about the implications of this difference and requests clarification.
  • One participant explains that gauge pressure reflects the pressure difference from atmospheric pressure, while total force includes atmospheric pressure, emphasizing that the total force accounts for the pressure the wall experiences even without water.

Areas of Agreement / Disagreement

Participants generally agree that the distinction between total force and force done by water is crucial, but there remains uncertainty about the implications of this difference and how to interpret the problem statements.

Contextual Notes

Participants highlight the importance of understanding the definitions of gauge pressure and absolute pressure, as well as the context of the problem statements, which may not have been fully explored.

Who May Find This Useful

Readers interested in fluid mechanics, particularly those grappling with the concepts of pressure and force calculations in different contexts.

Bassel
Messages
9
Reaction score
0
I've been solving fluid mechanics problems and i encountered two problems that made no sense to me. Both problems that ask about the force done by water on a VERTICAL wall under the level of water. One problem was solved by taking the integral of the gauge pressure and multiplying it by the area while the other was solved by also taking the integral of the gauge pressure and multiplying it by the area of the wall but after finding this value, the force due to atmospheric pressure was added. What happened There?? why two similar cases are solved in different meanings, anyone got any idea?
 
Physics news on Phys.org
The only difference that I can see between these two scenarios is that one is using gage pressure and the other is using absolute pressure. Maybe the problem statements have a hint as to why they were solved that way? My only guess as to why this was the case was possibly because one problem statement specifically asked for the force done by the water where as the other one asked for the total force?
 
YESS EXACTLY after looking to the problems again i realized that one asked about the total force and the other asked about the force done by water. but the problem is i don't know the difference and that is why i didn't realize the difference. Can You please give me a summary about the differences please between asking about force done by water and total force ? thanks a lot man sorry for bothering you.
 
Atmospheric pressure is the pressure caused by the atmosphere which is typically considered to be ~101325 Pa. Gage pressure is basically the difference between this number and the pressure that the point of interest is at since "normal conditions" are at atmospheric pressure. The force that is being applied only from the water is the force from the gage pressure; however, this value does not take into account the pressure that the object would typically experience if the water wasn't there and therefore does not take into account this force. If there was no water the wall would still see some force on it because of atmospheric pressure so if you want to find the total force you have to take that force into account as well. The main difference is one only asks for the change in force under normal circumstances where as the other one asks you for the total.
 
  • Like
Likes   Reactions: 1 person

Similar threads

  • · Replies 35 ·
2
Replies
35
Views
5K
  • · Replies 48 ·
2
Replies
48
Views
5K
  • · Replies 18 ·
Replies
18
Views
3K
  • · Replies 40 ·
2
Replies
40
Views
5K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 8 ·
Replies
8
Views
1K
  • · Replies 20 ·
Replies
20
Views
4K
  • · Replies 48 ·
2
Replies
48
Views
6K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K