Measurement · revision map · IGCSE 0625, Topic 1.1
TOPIC 1.1 · MEASUREMENT
CAMBRIDGE IGCSE PHYSICS 0625 · ONE-PAGE REVISION MAP
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MEASUREMENT1.1
SI Base Units
Every measurement has a number and a unit. The SI base units used here are:
- length → metre (m)
- mass → kilogram (kg)
- time → second (s)
Derived units build from these: m/s for speed, kg/m³ for density.
Unit Prefixes
A prefix scales a unit up or down by a power of ten.
- kilo (k) × 1000
- centi (c) ÷ 100
- milli (m) ÷ 1000
- micro (µ) ÷ 1 000 000
Measuring Length, Volume & Time
- Length: a ruler; small widths with a micrometer or calipers.
- Liquid volume: a measuring cylinder, read at the bottom of the meniscus.
- Time: a stopwatch; a pendulum beats steadily.
Measuring Well
Careful technique keeps errors small.
- Repeat a reading and take the average.
- Measure many together, then divide: time 20 swings of a pendulum, or measure a stack of 100 sheets of paper.
- Read scales straight on to avoid parallax error.
Scalars & VectorsEXTENDED
A scalar has size only. A vector has size and a direction.
Scalars
distance, speed, mass, time, energy
distance, speed, mass, time, energy
Vectors
displacement, velocity, acceleration, force, weight, momentum
displacement, velocity, acceleration, force, weight, momentum
Combining VectorsEXTENDED
Two vectors add to give a single resultant.
- Add them by a scale drawing (tip to tail).
- For two perpendicular vectors, find the resultant with Pythagoras.