
Physical quantities are either scalars or vectors.

Scalars don’t have a direction.

Vectors have a direction.


SI units

SI base units include:

m

kg

s

A

K


Derived units are based on base units, for example:

m/s

m/s^{2}

N (which really means kgm/s^{2})



Prefixes can be used if a unit is too big or too small for a purpose.

mega (M) means 1,000,000

kilo (k) means 1,000

deci (d) means 1 / 10

centi (c) means 1 / 100

milli (m) means 1 / 1,000

micro (µ) means1 / 1,000,000


Length measuring instruments

Ruler or measuring tape has an accuracy of ±1mm.

Vernier calipers has an accuracy of ±0.1mm.

Micrometer screwguage has an accuracy of ±0.01mm.
 To measure length using vernier calipers or micrometer screwguage:

Length = Main scale reading + Minor scale reading x Accuracy

Time measuring instruments

Stopwatch has an accuracy of ±0.01s

Tickertape timer has an accuracy of ± (1 / 50) of a second or ± (1 / 60) of a second.

Pendulum clock


Pendulum

Oscillation is a vibration.

Timeperiod is the time taken for one oscillation.

Amplitude is the maximum displacement from central position.

A pendulum of a particular length has a constant timeperiod. It is not affected by amplitude.

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