1.1Motion, Forces and Energy

Physical Quantities AND Measurement Techniques — Cambridge IGCSE Physics 0625 Revision Notes & Topical Questions

15 min read 25 parts Lesson 1 of 91 1 quiz

📚 Cambridge IGCSE Physics 0625 Hub / Topical Revision

0%read

Lesson summary

1.1 Physical quantities and measurement techniques — Notes — IGCSE PHYSICS notes: Choose and use instruments for length, volume and time, reduce error with multiple readings, and distinguish scalars from vectors.Ruler — it measures small distances of a few centimetres to the near…

Tape measure
Reading a scale
Extended instruments
Measuring cylinder
Irregular solid
Digital timers

Part 1 of 7Measuring length

Ruler

Ruler it measures small distances of a few centimetres to the nearest millimetre, in cm or mm

Tape measure

Tape measure it measures lengths of tens of centimetres and more

Reading a scale

Reading a scale look straight at the mark to avoid parallax error

Extended instruments

Extended instruments vernier calipers read to 0.1 mm and a micrometer screw gauge reads to 0.01 mm
They suit small objects such as the diameter of a wire.

Part 2 of 7Measuring volume

Measuring cylinder

Measuring cylinder it measures the volume of a liquid in cm³ (1 cm³ = 1 mL)

Reading

Reading read the bottom of the meniscus with the eye level with the liquid

Irregular solid

Irregular solid put it in water and find the change in volume reading

Regular solid

Regular solid calculate the volume from its dimensions, for example length × width × height for a cuboid

Part 3 of 7Measuring time

Clocks

Clocks they usually measure long time intervals

Digital timers

Digital timers stopwatches measure short time intervals

Reaction time

Reaction time an alert person has a human reaction time of about 0.2 to 0.3 s

Effect

Effect reaction time matters most when the time measured is very short

Part 4 of 7Multiple readings

Purpose

Purpose taking multiple readings reduces the effect of measurement errors and improves precision

Small measurements

Small measurements if the measurement is small, the percentage uncertainty is large

Thin objects

Thin objects measure many identical items and divide
The thickness of 100 sheets of paper divided by 100 gives the thickness of one sheet.
The total length of four ball bearings divided by four gives the diameter of one.

Oscillations

Oscillations time many swings and divide
Timing 10 oscillations and dividing by 10 reduces the reaction-time error for the time of one oscillation.

Reference marker

Reference marker a line or dot at the equilibrium position that makes it easier to see when the pendulum passes,

reducing the starting and stopping error

Part 5 of 7Scalars and vectors

Scalar

Scalar a quantity with magnitude only

Vector

Vector a quantity with both magnitude and direction

Level

Level this is Extended tier content

Distance and displacement

Distance and displacement distance is a scalar and displacement is a vector

Speed and velocity

Speed and velocity speed is a scalar and velocity is a vector

Examples of scalars

Examples of scalars distance, speed, time, mass, energy, temperature

Examples of vectors

Examples of vectors displacement, velocity, force, weight, acceleration, momentum

Part 6 of 7Resultant of two vectors at right angles

Diagram

Diagram a sketch is enough if the resultant and the components are labelled

Magnitude

Pythagoras gives FR² = F1² + F2²

Angle

Angle tan θ = opposite ÷ adjacent, so θ = tan⁻¹(F1 ÷ F2)

Result

Result state both the magnitude and the direction

Limit

Limit in this course the resultant of two vectors is for forces and velocities only

Scale drawing

Scale drawing draw the vectors at right angles to a scale, complete the rectangle and measure the diagonal and its angle

Part 7 of 7More from the specification

1Measuring time

Measuring time a stopwatch measures seconds and a runner's time is taken from start to finish, with reaction time adding error

2Typical measurements

Typical measurements length is measured with a ruler or micrometer, and repeating readings then averaging improves reliability

3Timing many swings

Timing many swings measuring a long interval and dividing gives a more precise value for a single short period

4An arrow on a diagram

An arrow on a diagram shows the direction of a vector quantity such as velocity or force, unlike scalars which have size only

5Measuring time

Measuring time a stopwatch measures seconds and a runner's time is taken from start to finish, with reaction time adding error

6Typical measurements

Typical measurements length is measured with a ruler or micrometer, and repeating readings then averaging improves reliability

7Timing many swings

Timing many swings measuring a long interval and dividing gives a more precise value for a single short period

8An arrow on a diagram

An arrow on a diagram shows the direction of a vector quantity such as velocity or force, unlike scalars which have size only

Key terms

Term	Meaning
Scalar	Quantity with magnitude only.
Vector	Quantity with magnitude and direction.
Displacement	Straight-line distance in a stated direction.
Reaction time	Delay between seeing an event and pressing the timer, about 0.2 to 0.3 s.
Resultant	Single vector with the same effect as two or more vectors.
Reference marker	Fixed mark showing the equilibrium position of an oscillation.

Avoid these mistakes

Taking a single short timing by hand — reaction time of 0.2 to 0.3 s makes it unreliable; time many oscillations and divide.

Reading a measuring cylinder from above or below — keep the eye level with the bottom of the meniscus.

Treating speed and velocity as the same — velocity has a direction.

Treating mass as a vector — mass is a scalar and weight is the vector.

Last updated: 15 October 2026