Physical meaning of a Metre-Second? [or (Kg · s) or (N · s) ]

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SUMMARY

The discussion centers on the physical interpretation of the unit 'metre-second' (m·s) and its relevance in various contexts, particularly in relation to dynamic viscosity and momentum. The unit of dynamic viscosity is expressed as kilogram per metre second (Kg/m·s), which is equivalent to pascal-second (Pa·s). Additionally, the standard unit of momentum is kilogram-metre per second (kg·m/s), which translates to Newton-second (N·s) in SI units. Participants explore the conceptualization of these units in practical scenarios, emphasizing their application in measuring impulse and mass eccentricity.

PREREQUISITES
  • Understanding of SI units and their conversions, particularly pascal-second (Pa·s) and Newton-second (N·s).
  • Familiarity with dynamic viscosity and its significance in fluid mechanics.
  • Knowledge of momentum and its relationship with force and time.
  • Basic grasp of impulse and its calculation as the product of force and time.
NEXT STEPS
  • Research the concept of impulse and its mathematical representation in physics.
  • Explore the applications of dynamic viscosity in engineering and fluid dynamics.
  • Study the relationship between mass, distance, and force in the context of mechanical systems.
  • Investigate the implications of mass eccentricity in rotating machinery and its effects on performance.
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Physicists, engineers, and students in mechanics or fluid dynamics who seek to deepen their understanding of physical units and their applications in real-world scenarios.

CF.Gauss
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We all understand what metres PER second (m/s) physically means... but,
What I was wondering was what does a 'metre-second' actually mean? Or does it have a physical meaning at all!

As an example:

If we take the units for Dynamic viscosity we have:

Kilogram per metre second ( Kg / m.s )

On a side note, in relation to my above example:
The SI physical unit of dynamic viscosity is the pascal-second (Pa·s), which is identical to
Kg. m-1.s-1 = Kg / (m s)


Another example, of a similar type, would be the standard unit of momentum, which is:
Kilogram-metre per second (kg · m/s or kg · m · s-1 ) which in SI units is equal to Newton-second (N · s)

In this example we have both a Kilogram-metre and, in SI, a Newton-second!
I can easily conceptualise the idea of, say, 1 Metre every 1 Second (m/s) but I am finding it hard to conceptualise this concept!

How exactly could one have, in the physical world, a metre-second (m · s), kilogram-metre (Kg · m) or Newton-second (N · s)?
 
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If you could snort a white powdery substance from the surface of a mirrored conveyer belt moving at a fixed speed using a stationary rolled up piece of currency with a diameter measured in meters and had a certain number of seconds to do so, the "meter second" could be used as a relevant measure.
 
jbriggs444 said:
If you could snort a white powdery substance from the surface of a mirrored conveyer belt moving at a fixed speed using a stationary rolled up piece of currency with a diameter measured in meters and had a certain number of seconds to do so, the "meter second" could be used as a relevant measure.

:smile: :smile:


CF.Gauss said:
We all understand what metres PER second (m/s) physically means... but,
What I was wondering was what does a 'metre-second' actually mean? Or does it have a physical meaning at all!

As an example:

If we take the units for Dynamic viscosity we have:

Kilogram per metre second ( Kg / m.s )

On a side note, in relation to my above example:
The SI physical unit of dynamic viscosity is the pascal-second (Pa·s), which is identical to
Kg. m-1.s-1 = Kg / (m s)


Another example, of a similar type, would be the standard unit of momentum, which is:
Kilogram-metre per second (kg · m/s or kg · m · s-1 ) which in SI units is equal to Newton-second (N · s)

In this example we have both a Kilogram-metre and, in SI, a Newton-second!
I can easily conceptualise the idea of, say, 1 Metre every 1 Second (m/s) but I am finding it hard to conceptualise this concept!

How exactly could one have, in the physical world, a metre-second (m · s), kilogram-metre (Kg · m) or Newton-second (N · s)?

Never used metre-second but for something like the N*s, it would be the force acting over a period of time such that the Impulse = Force*time

For something like kg-m, this could be something like a mass acting a distance. For example, if you have a shaft with an unbalance in it (center of rotation does not coincide to where the mass acts), you quantify the unbalance as a mass-eccentricity.

Mass eccentricity me = mass*distance, usually given in gram-cm or some unit like that.
 
rock.freak667 said:
Never used metre-second but for something like the N*s, it would be the force acting over a period of time such that the Impulse = Force*time

would the force acting over a period of time not be Newtons per second ( N/s )?
 
Last edited:
CF.Gauss said:
would the force acting over a period of time not be Newtons per second ( N/s )?

That would give you the rate of change of force. A typical Force-time graph looks like this:

09_03Figure.jpg



The area under the graph gives the impulse which is the same as the change in momentum.
 
jbriggs444 said:
If you could snort a white powdery substance from the surface of a mirrored conveyer belt moving at a fixed speed using a stationary rolled up piece of currency with a diameter measured in meters and had a certain number of seconds to do so, the "meter second" could be used as a relevant measure.
Very good!
I thought of a tunnel's price (tunnel length multiplied time of realization) but you beat me...
 

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