Is there any physical quantity having two different units?

[Aaditya Jain]

Is there any physical quantity having two different units or can it be possible that a physical quantity have two different units?

 

[256bits]

Hi Aaditya,
Not quite sure what you are asking?
Velocity uses two units, such as meter / sec - a length unit and a time unit.

 

[Aaditya Jain]

Good to hear from you. I am saying can a quantity have two different formula's having different units, if it acts under different conditions?

 

[Herman Trivilino]

A quantity such as distance can have units of meters or units of feet.

 

[sophiecentaur]

The base units have to be the same but there are plenty of examples where different disciplines use different units. One well known example would be the use of Joules (J) and electron Volts (eV) for energy of particles. eV is very convenient because the charge on every electron is the same so the accelerating Voltage is a very handy measure to use. We also describe many EM waves in terms of wavelength and frequency - depending on convenience.
The list goes on.

 

[PeroK]

Is there any physical quantity having two different units or can it be possible that a physical quantity have two different units?

In the geometrised units of GR, time and mass can be measured in units of length. The mass of the Sun, for example, is about $3km$.

 

[suremarc]

There‘s the case of torque, which is measured in N m (Newton meters). Formally equivalent to energy (1 N m = 1 J), but you have to integrate torque against angular displacement to calculate work. I had always found this curious in high school.

 

[Dale]

I am saying can a quantity have two different formula's having different units

Maxwell’s equations have both different units and different formulas in SI units and in CGS units.

 

[ZapperZ]

Good to hear from you. I am saying can a quantity have two different formula's having different units, if it acts under different conditions?

This still doesn't explain anything.

The electric field strength can be written in units of V/m or N/C. Are these "different" enough for you?

Zz.

 

[Aaditya Jain]

I mean to says different unit in dimension. Means, can it be possible that unit of a physical quantity equals to kgm2/s2 and kgm3s5, if it acts under different conditions.

 

[Aaditya Jain]

Hi Aaditya,
Not quite sure what you are asking?
Velocity uses two units, such as meter / sec - a length unit and a time unit.

I mean to says different units in dimension. Means, can it be possible that a physical quantity has unit equals to kgm2/s2 and kgm3s5, if it acts under different conditions.

 

[LagrangeEuler]

Yes. For example in quantum mechanics wave function $\psi(\vec{r},t)$ depends on dimension of problem. In one dimensional system it is $L^{-1/2}$, in two dimensional is $L^{-1}$ and in three dimensional is $L^{-3/2}$, where $L$ is lenght.

 

[256bits]

I mean to says different units in dimension. Means, can it be possible that a physical quantity has unit equals to kgm2/s2 and kgm3s5, if it acts under different conditions.

Well it won't be the same physical quantity proper if the units are different.

But as @LagrangeEuler has replied, we can state something similar depending.
As an example,
Force acting at a point would be in Newtons.
An extended force could be expressed as Nt/m, such as that acting over a certain length of beam.
Or as Nt/m² if the force is extended over a surface area.
These are called distributed forces.

 

[Dadface]

There‘s the case of torque, which is measured in N m (Newton meters). Formally equivalent to energy (1 N m = 1 J), but you have to integrate torque against angular displacement to calculate work. I had always found this curious in high school.

I think that's a good example of two different physical quantities having the same units ( as distinct from two different units applying to the same physical quantity )
The difference between our definitions of torque and energy is that in the former case the relevant component force and distance are at 90 degrees to each other and in the latter case they are in the same direction.

 

[nasu]

If they had different formulas, different units and apply to different conditions, by what logic would you even call them "the same quantity"?

 

[Herman Trivilino]

The difference between our definitions of torque and energy is that in the former case the relevant component force and distance are at 90 degrees to each other and in the latter case they are in the same direction.

For the maximum values, what you say about the outcome of the definitions is true; but that's not even relevant.

 

[Dadface]

For the maximum values, what you say about the outcome of the definitions is true; but that's not even relevant.

Sorry I don't understand your comment. Energy and Torque are completely different quantities which can both be expressed in the same units. But why "for the maximum values"?

 

[Herman Trivilino]

But why "for the maximum values"?

These are the conditions under which you get the maximum values:

The difference between our definitions of torque and energy is that in the former case the relevant component force and distance are at 90 degrees to each other and in the latter case they are in the same direction.

 

[dfmd]

Vitamin D is measured in functional units. If you immerse a half naked human in sunlight for a half hour, that human's skin will produce 20,000 units of cholecalciferol (nubile viamin D).
One mg of Vitamin D also equals 40,000 units. A tiny bit goes a long way.
The unit is a functional element while a milligram is your Newtonian classical mass.

 

[Dadface]

The difference between our definitions of torque and energy is that in the former case the relevant component force and distance are at 90 degrees to each other and in the latter case they are in the same direction.

These are the conditions under which you get the maximum values:

I'm still not sure what you mean by this. Whether the values be maximum or not the difference I described still holds. Also, I did not describe situations where you get maximum values, I referred to relevant "component" quantities which, depending on the relevant angles, can give values anywhere between the maximum possible and zero. I will try to describe the difference but very informally:

In the definition of work the distance referred to is the distance moved.
In the definition of torque the distance referred to is the distance between two points on whatever it is that the torque is applied to.