Momentum and Pressure and Forces

Click For Summary

Homework Help Overview

The discussion revolves around the relationship between force, pressure, and velocity, exploring theoretical concepts in physics. Participants examine the implications of two formulas: one relating pressure to force and velocity, and another relating force to momentum.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants analyze the apparent contradiction between the derived relationship of force being proportional to velocity squared and the established notion of force being directly proportional to velocity. They also discuss the implications of the dot product in the context of work.

Discussion Status

The conversation has progressed with some participants providing clarifications and insights into the relationships discussed. There is an ongoing exploration of the mathematical relationships and their interpretations, but no consensus has been reached on the initial question posed.

Contextual Notes

Participants are navigating through theoretical concepts and mathematical interpretations, with some expressing confusion about formatting in the discussion. The original poster seeks clarification on the relationships between the physical quantities involved.

Pawnag3
Messages
8
Reaction score
0
This is a theoretical question that I have, it might be somewhat elementary, or I might be missing something. Basically, we have two formulas:
1) We know that
P = F/A
By multiplying by d/d, we get:
P = Work/Volume
P = Energy/Volume
P = 1/2 mv2 / V
Therefore
F/A = 1/2 mv2 / V
And therefore, the force is equal to the velocity squared.
2) However, according to F*t = mv
We say that Force is directly proportional to velocity.

Do you see the contradiction?
Please Help

Note: I'm basically comparing the relationship of force with respect to velocity
 
Physics news on Phys.org
Pawnag3 said:
F/A = 1/2 mv2 / V
And therefore, the force is equal to the velocity squared.
2) However, according to F*t = mv
We say that Force is directly proportional to velocity.

Do you see the contradiction?

in the first sentence
[tex] \frac{F}{A}=\frac{1}{2}\frac{mv^2}{V}[/tex]
Now when you bring the area on the other side A/V becomes 1/length or 1/distance and cancels with one (length)2 of velocity ... hence there is only one velocity term left and hence F proportional to v.

Another mistake is you have considered F*d=Work but actually its the dot product between them.

Rem: F/A is proportional to v2 not force!
 
Umm, thanks, that clarifies everything :D
But I have one question:
1) How did you make the formatting look so nice? :D
I couldn't figure it out (but then again, I didn't spend too much time, under which heading is it? :P)
 
Pawnag3 said:
Umm, thanks, that clarifies everything :D
But I have one question:
1) How did you make the formatting look so nice? :D
I couldn't figure it out (but then again, I didn't spend too much time, under which heading is it? :P)

I used latex or tex as its called ... you can learn it here
https://www.physicsforums.com/showthread.php?t=386951
 
Last edited by a moderator:

Similar threads

  • · Replies 9 ·
Replies
9
Views
2K
Replies
335
Views
17K
  • · Replies 23 ·
Replies
23
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 25 ·
Replies
25
Views
2K
  • · Replies 10 ·
Replies
10
Views
1K
Replies
3
Views
1K
  • · Replies 27 ·
Replies
27
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
Replies
19
Views
3K