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Does there exist a negative dimensionless quantity?
att.
I am just wondering if there exists a negative dimensionless quantity? It seems that all dimensionless numbers I encount in my field (fluid dynamics) are positive. what if it is negative? and if negative, what does that mean? I sense that:
the imposed negative sign for a dimensionless number is just an alternative expression for a special external boundary condition, rather than no longer a characteristics over an essential in a physical law that required for being independent of external boundary conditions.
Have you ever encounted any dimensionless quantities negative?
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Hello, 1. Strains are
Hello,
1. Strains are dimensionless and can have positive or negative signs depending on the sign convention chosen for tensile or compressive strains.
2. Poisson's ratio can be negative for certain exotic materials and Poisson's ratio is a dimensionless number.
3. Mach number less than zero would be hard to interpret. It is hard to imagine what it would mean for something to go less then 0 speed.
4. I can imagine a negative drag coefficient. It would mean that the applied force on an object due to air is acting in the same direction as the object travels. This would be strange indeed. Could you construct an object that has less than zero air resistance as it goes faster through the air? Well, we can imagine this, but it is likely not possible.
Just some random thoughts, but case 1 and 2 above do give cases of negative dimensionless numbers.
regards,
Louie
exactly, thank you, Louie
transport
thanks.
transport