Physics OCR Chapter 2 (Foundations of Physics)

Quantities and Units

Quantity - Is a property of an object or a phenomenon that can be measured

Scientists use a standard system of units abbreviated to SI

SI Base Units

SI is built around seven base units, which are the standard set of units

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Prefixes

SI uses prefixes to show multiples of factors of the units.

e.g. km = Kilometer (The prefix is 'Kilo' the SI base unit is 'meter')

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Scalar Quantities - Has a magnitude but no direction

Scalar quantities can be added and subtracted together in the usual way
Scalar quantities must have the same units when added or subtracted
Scalar quantities can also be divided or multiplied together and the units can be the same or different, final units have to be worked out

Vector Quantities - Has magnitude and direction

Vectors in parallel and antiparallel are added
Perpendicular Vectors:
- Perpendicular vectors act at right angles to one another
- You can use Pythagoras theorem to find magnitude of the resultant vector
- You can use trigonometry to find the angle

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Resolving Vectors into Two Components

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