Units: Ep.3
When we measure a quantity, we always compare it with some reference standard.
Such a standard defines a unit of the quantity.
The meter is a unit of distance, and the second is a unit of time.
When we use a number to describe a physical quantity, we must always specify the unit that we are using; to describe a distance as simply “4.53” wouldn’t mean anything.
Ref: University Physics by Hugh D. Young, Roger A. Freedman (exercise: 1.3)
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