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 Im 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)?