Physical quantities and measurement techniques
Cambridge IGCSE Physics (0625) · Unit 1: Motion, forces and energy · 14 flashcards
Physical quantities and measurement techniques is topic 1.1 in the Cambridge IGCSE Physics (0625) syllabus
, positioned in Unit 1 — Motion, forces and energy , alongside Motion, Mass and weight and Density.
In one line: Scalar quantities: energy, mass, speed.
Vector quantities: displacement, force, velocity.
Scalar quantities only have magnitude; vector quantities have both magnitude and direction.
This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 confirm this is a high-yield topic: Cambridge has set undefined questions worth 465 marks here (about 7.3% of all Physics marks across those years).
The deck below contains 14 flashcards — 3 definitions — covering the precise wording mark schemes reward. Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
State whether each of the following physical quantities are scalar or vector: displacement, energy, force, mass, speed, velocity
Scalar quantities: energy, mass, speed.
Vector quantities: displacement, force, velocity.
Scalar quantities only have magnitude; vector quantities have both magnitude and direction.
What the Cambridge 0625 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- Describe Describe the use of rulers and measuring cylinders to find a length or a volume
- Describe Describe how to measure a variety of time intervals using clocks and digital timers
- Determine Determine an average value for a small distance and for a short interval of time by measuring multiples (including the period of oscillation of a pendulum)
- Understand Understand that a scalar quantity has magnitude (size) only and that a vector quantity has magnitude and direction Supplement
- Know Know that the following quantities are scalars: distance, speed, time, mass, energy and temperature Supplement
- Know Know that the following quantities are vectors: force, weight, velocity, acceleration, momentum, electric field strength and gravitational field strength Supplement
- Determine Determine, by calculation or graphically, the resultant of two vectors at right angles, limited to forces or velocities only Supplement
Describe how you would accurately measure the length of a small metal rod using a ruler, minimizing parallax error.
1. Place the ruler alongside the metal rod.
2. Ensure the ruler is aligned parallel to the rod to avoid skew measurements.
3. Place the zero mark of the ruler at one end of the rod.
4. Read the value on the ruler where the other end of the rod aligns.
5. Position your eye directly above the reading to avoid parallax error (looking at an angle will give a false reading). Record this value as the length.
A student uses a measuring cylinder to find the volume of 10 identical marbles. State three precautions they should take to obtain an accurate measurement.
1. Ensure the measuring cylinder is placed on a flat, level surface to avoid a tilted reading.
2. Read the meniscus at eye level to avoid parallax error.
3. Before adding the marbles, record the initial water volume in the cylinder.
Describe how you would accurately measure the time it takes for a pendulum to complete 10 full swings using a stopwatch.
1. Start the stopwatch as the pendulum is released for its first swing.
2. Count the number of complete swings (1 full swing = there and back).
3. Stop the stopwatch after 10 complete swings.
4. Divide the total time recorded on the stopwatch by 10 to find the average time for one swing. This reduces error.
A student uses a digital timer to measure the time for a ball to roll down a ramp. They perform three trials and record the following times: 2.1 s, 2.2 s, and 2.7 s. State one way the student could improve the accuracy of their measurement.
The student could perform more trials and calculate the average time. This will reduce the impact of random errors.
A pendulum completes 20 oscillations in 36 seconds. Calculate the average period of one oscillation.
Period (T) = Total time / Number of oscillations
T = 36 s / 20
T = 1.8 s
The period is found by dividing the total time by the number of oscillations. This gives a more accurate value than timing just one swing.
State why it is more accurate to measure the time for multiple oscillations of a pendulum when determining the average period, rather than measuring just one oscillation.
Measuring multiple oscillations reduces the percentage error caused by the reaction time when starting and stopping the timer. The error is spread over a larger time interval, thus reducing its impact on the final calculated period. Also helps to reduce systematic errors.
State whether each of the following physical quantities are scalar or vector: displacement, energy, force, mass, speed, velocity.
Scalar quantities: energy, mass, speed.
Vector quantities: displacement, force, velocity.
Scalar quantities only have magnitude; vector quantities have both magnitude and direction.
A car travels 200 m North, then 150 m East. Explain why the total distance travelled by the car is different from the magnitude of the car's overall displacement.
Distance is the total length of the path travelled. Displacement is the straight-line distance from the starting point to the ending point, along with the direction.
Distance = 200 m + 150 m = 350 m. Distance is a scalar quantity.
Displacement = √(200² + 150²) = 250 m. Since displacement considers direction, it is calculated by a straight line rather than the overall distance travelled. Displacement is a vector quantity.
State three scalar quantities.
1. Distance
2. Time
3. Mass
Scalar quantities are defined by magnitude only, not direction.
A car travels a distance of 120 m in 4 s. Energy transferred in this time is 2400J. Which of these quantities is a scalar quantity?
Distance, Time and Energy are all scalar quantities. They are defined by magnitude only and do not have a direction.
State four vector quantities.
1. Force
2. Velocity
3. Acceleration
4. Momentum
A vector quantity has both magnitude and direction.
A car accelerates from rest to a velocity of 20 m/s East in 5 seconds. Explain why velocity is a vector quantity, while speed is a scalar quantity.
Velocity is a vector quantity because it specifies both the magnitude (20 m/s) and direction (East). Speed, on the other hand, only provides the magnitude (20 m/s) and does not include any directional information. Therefore, speed is a scalar quantity.
A boat travels east across a river at 3.0 m/s. The river current flows south at 4.0 m/s. Calculate the magnitude of the boat's resultant velocity.
1. Formula: v = √(v_east² + v_south²)
2. Substitution: v = √(3.0² + 4.0²)
3. Calculation: v = √(9 + 16) = √25 = 5.0 m/s
*Explanation: The boat's eastward velocity and the river's southward velocity are perpendicular vectors. The resultant velocity is the hypotenuse of the right-angled triangle formed by these two vectors.*
A force of 9.0 N acts horizontally on an object. A second force of 12.0 N acts vertically upwards on the same object. Describe how you would determine the direction of the resultant force.
1. Diagram: Draw a right-angled triangle. One side represents the 9.0 N horizontal force, and the other represents the 12.0 N vertical force.
2. Trigonometry: Use trigonometry (specifically, the tangent function) to find the angle (θ) between the horizontal and the resultant force. tan(θ) = opposite/adjacent = 12.0/9.0
3. Calculate: θ = tan⁻¹(12.0/9.0) ≈ 53.1°
4. Direction: State the direction as approximately 53.1° upwards from the horizontal.
Key Questions: Physical quantities and measurement techniques
State whether each of the following physical quantities are scalar or vector: displacement, energy, force, mass, speed, velocity.
Scalar quantities: energy, mass, speed.
Vector quantities: displacement, force, velocity.
Scalar quantities only have magnitude; vector quantities have both magnitude and direction.
State three scalar quantities.
1. Distance
2. Time
3. Mass
Scalar quantities are defined by magnitude only, not direction.
State four vector quantities.
1. Force
2. Velocity
3. Acceleration
4. Momentum
A vector quantity has both magnitude and direction.
Tips to avoid common mistakes in Physical quantities and measurement techniques
- ● Read questions closely: if it asks for a measuring instrument, don't give a unit of measurement.
- ● Strive for maximum precision when measuring small objects: read to the nearest mm if your ruler allows.
- ● When measuring tiny objects, use the smallest scale divisions your instrument provides.
- ● When describing isotopes, specify the exact neutron difference in the nucleus: 'one less neutron' versus 'one more neutron'.
- ● The main technique for setting up the experiment is being as close to perpendicular to the surface as possible.
More topics in Unit 1 — Motion, forces and energy
Physical quantities and measurement techniques sits alongside these Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
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Cambridge syllabus keywords to use in your answers
These are the official Cambridge 0625 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Key terms covered in this Physical quantities and measurement techniques deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
Related Physics guides
Long-read articles that go beyond the deck — cover the whole subject's common mistakes, high-yield content and revision pacing.
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