Home » Handbook of O Level Physics » UNIT 1: MEASUREMENT OF QUANTITIES

# UNIT 1: MEASUREMENT OF QUANTITIES

• 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/s2

• N (which really means kgm/s2)

• 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:

• Time measuring instruments

• Stopwatch has an accuracy of ±0.01s

• Ticker-tape timer has an accuracy of ± (1 / 50) of a second or ± (1 / 60) of a second.

• Pendulum clock

• Pendulum

• Oscillation is a vibration.

• Time-period is the time taken for one oscillation.

• Amplitude is the maximum displacement from central position.

• A pendulum of a particular length has a constant time-period. It is not affected by amplitude.