Unit 1 Physical Quantities and units

Physical Quantity

A feature of something which can be measured

Order of magnitude

The power of ten to which the number is raised

SI base units

Standard units of measurement

SI derived units

Units which are combinations of the base units of the SI system

Accuracy

An accurate value of a measured quantity which is close to the true or known value

Precision

how close a set of measured values are to each other

Errors (Systematic, Random and Zero error)

Systematic error- An error due to faulty apparatus

Random error- Error made by the person carrying out the measuring

Zero error- A systematic error in an instrument that gives a non-zero reading when the true value of a quantity is zero

Uncertainty (Definition)

the total range of values within which the measurement is likely to lie

Absolute Uncertainty formula

Relative Uncertainty formula

Percentage uncertainty formula

Scalar quantity

has magnitude only

ex: speed, energy, power, work, mass, distance

Vector

has magnitude and direction

ex: displacement, acceleration, force, velocity, momentum, weight, electric field strength

Pythagoras theorem

Sine and Cosine rule