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Answers to the most popular questions about NPL and our activities.
12 am,12 pm, midday and midnight meaning and the 24-hour clock.
Historically, there have been a variety of units of force and conversion factors.
There are no official definitions of the duration of spring, summer, autumn and winter.
All objects at temperatures above absolute zero emit thermal radiation.
We use these words on a daily basis, but do you really know the difference between mass, weight, force and load?
Density and specific gravity are both used to describe mass and can be used to compare substances.
Atmospheric pressure reduces with altitude for two reasons, both of which are related to gravity.
A platinum resistance thermometer (PRT) contains a piece of platinum wire, whose electrical resistance is proportional to temperature.
What can you do to ensure you receive the correct time?
The term g-force is used to convey values of force and acceleration.
The definition of a vacuum is not precise but is commonly taken to mean pressures below, and often considerably below, atmospheric pressure.
Want more detail? Delve into the subjects more deeply.
The SI units
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