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Summary of basic ideas needed for
There are six base quantities that you need for
A-level (time, length, mass, temperature, electric
current and amount of substance). All other
quantities are derived from these.
For an equation to be correct it must be
homogenous. This means that all the terms have
the same units. But remember, a homogenous
equation may not be entirely right.
You should always give your numerical answers to
the correct number of significant figures.
Scalars have size (magnitude) only
Vectors have size (magnitude) and direction. Vectors
are represented by arrows.
When vectors are added together to find the
resultant, we must take account of their direction.
For vectors acting along the same straight line we
take one direction as positive and the other as
To add two perpendicular vectors you can use
pythagoras' theorem a2 + b2 = c2
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A single vector can be resolved to find its effect in
two perpendicular directions. The component of a
vector in any direction is found by multiplying the
vector by the cosine of the angle between the
vector and the required direction.
Subtracting a vector is the same as adding a vector
of the same size, acting in the opposite direction.…read more