MHB Find an Equivalent Law for Dimensionless Quantities

  • Thread starter Thread starter evinda
  • Start date Start date
  • Tags Tags
    Equivalent Law
Click For Summary
The discussion focuses on finding an equivalent law for a physical system described by the equation f(E,P,A)=0, where E, P, and A represent energy, pressure, and area, respectively. The user initially believes that the number of fundamental units is equal to the number of dimensional quantities, suggesting that Buckingham's π theorem cannot be applied. However, other participants clarify that the chosen units are correct and interdependent, indicating that Buckingham's theorem can still be utilized. The conversation emphasizes the need to explore the application of dimensionless quantities despite initial doubts. Overall, the thread highlights the importance of understanding dimensional analysis in physical laws.
evinda
Gold Member
MHB
Messages
3,741
Reaction score
0
Hello! (Wave)

A physical system is described by a law of the form $f(E,P,A)=0$ where $E,P,A$ represent, respectively, enery, pressure and area of surface. Find an equivalent law that relates suitable dimensionless quantities.

I have tried the following:

The fundamental units are:

Mass: $M$, Length: $L$, Time: $T$.

Thus:
$$[E]=ML^{2}T^{-2} \\ [P]=ML^{-1}T^{-2} \\ [A]=L^2$$

In this case, the number of fundamental units is equal to the number of the quantities with dimensions, so we cannot apply Buckingham $\pi$ theorem , right?

But how else can we find an equivalent law that relates suitable dimensionless quantities? (Thinking)

Or have I done something wrong at the choice of the fundamental units? :confused:
 
Mathematics news on Phys.org
Hey! (Blush)

Those units are correct and they are dependent on each other.
I think that means that we can still apply Buckingham's theorem.
Did you try? (Wondering)
 
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

Similar threads

  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 10 ·
Replies
10
Views
6K
  • · Replies 7 ·
Replies
7
Views
1K
  • · Replies 9 ·
Replies
9
Views
3K
Replies
3
Views
4K
Replies
8
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
537
  • · Replies 5 ·
Replies
5
Views
2K