Physics (AS)·General physics · NSSCAS 1.1
Physical quantities & units
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Every measurement in physics is a magnitude paired with a unit — nothing more, nothing less. In this Advanced Subsidiary lesson we build the SI system from the ground up: the seven base quantities and their units, how every other unit is a product or quotient of these bases, and how to use base units to check that an equation is homogeneous. We meet the SI prefixes from pico to tera, learn to make sensible order-of-magnitude estimates, and then turn to scalars and vectors — adding and subtracting coplanar vectors tip-to-tail and by components, and resolving a single vector into two perpendicular components. This is the foundation the whole of AS Physics stands on.
What you'll learn in this lesson
By the end you should be able to (NSSCAS Physics (AS) 1.1):
- Recall that every physical quantity consists of a numerical magnitude and a unit
- Make reasonable order-of-magnitude estimates of physical quantities
- Recall and use the SI base quantities and their units: mass (kg), length (m), time (s), current (A), temperature (K), amount of substance (mol), and luminous intensity (cd)
- Express derived units as products or quotients of the SI base units
- Use SI base units to check the homogeneity of physical equations
- Use the prefixes pico, nano, micro, milli, centi, deci, kilo, mega, giga and tera
- Distinguish between scalar and vector quantities and give examples of each
- Add and subtract coplanar vectors tip-to-tail and by components
- Resolve a single vector into two perpendicular components
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