Why can a factor such as be multiplied to any physical quantity without changing its…

PHYSICS · Single correct · CBSE · Physics · Units and Measurements · Units and Measurements

Problem

Why can a factor such as 1 km1000 m\dfrac{1\,\text{km}}{1000\,\text{m}} be multiplied to any physical quantity without changing its value? (a) Any ratio whose numerator and denominator have the same physical dimension can be inserted into a calculation, irrespective of its numerical value. (b) Since a kilometre is larger than a metre, putting the larger unit in the numerator keeps the overall product unchanged. (c) Its numerical value equals 1 and it is dimensionless. (d) Multiplying by 1 km1000 m\dfrac{1\,\text{km}}{1000\,\text{m}} merely changes the units to kilometres; the numerical value will readjust later, so the physical quantity remains the same.

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