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Edexcel IGCSE Physics revision

Edexcel IGCSE Physics Forces and motion units questions

Revise the syllabus content for Forces and motion units, learn how to approach common exam questions, and study two worked examples with clear diagrams.

Edexcel IGCSE Physics Subtopic 1.a

Forces and motion units syllabus

Questions on forces and motion units can test recall, calculations, explanations, diagrams, data handling and practical skills. You should be able to:

  • 1.1 use the following units: kilogram (kg), metre (m), metre/second (m/s), metre/second² (m/s²), newton (N), second (s) and newton/kilogram (N/kg)
  • 1.2P use the following units: newton metre (Nm), kilogram metre/second (kg m/s)

How to answer forces and motion units questions

  1. Write the unit symbol exactly and distinguish quantities that use similar-looking units.
  2. Convert prefixes and compound units before substituting values into an equation.
  3. Check that the unit of the final answer matches the quantity asked for.
  4. Use the context of a diagram or calculation to reject units with the wrong dimensions.

Forces and motion units example questions and worked answers

These examples show how information in a diagram, graph or experimental context becomes part of a complete exam answer.

Example 1: Using a Diagram

Question 1

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Turn over
A student measures the circumference of a circular pipe.
He wraps a length of string around the pipe five times and marks it with ink, as shown in the photograph.
Photograph of a circular pipe with string wrapped around it five times and ink marks indicating turns.
The student unwraps the string and holds it against a ruler with a centimetre scale.
The next photograph shows the first two ink marks on the string.
Photograph of string with two ink marks laid against a ruler with centimetre markings (around 41 cm to 48 cm visible).
The student measures the diameter of the pipe using a digital calliper.
The calliper shows that the diameter is 15.10 mm.
Calculate the circumference of the pipe using the formula
circumference = diameter × π
Photograph of a digital calliper measuring the diameter of a circular pipe; digital display shows 15.10 mm.
calculated circumference = cm

Final answer

Calculated circumference = 4.744 cm (or 4.74 cm).

Mark scheme points

  1. M1 Correct substitution of the diameter into the formula, including conversion from millimetres to centimetres.
  2. M2 Correct calculation giving a circumference of 4.744 cm, or an accepted rounded value such as 4.7 cm or 4.74 cm.

Explanation

Convert the diameter to centimetres because the required answer is in centimetres:

15.10 mm = 1.510 cm

circumference = diameter × π
               = 1.510 × 3.142
               = 4.74442 cm
               ≈ 4.744 cm

Therefore, the circumference is 4.744 cm. A value of 4.74 cm is also suitably rounded.

Common mistakes

  • Using 15.10 directly without converting from millimetres gives an answer in millimetres, not centimetres.
  • Do not multiply by the diameter twice; the given formula is circumference = diameter × π.
  • Include the unit cm in the final answer.

Example 2: Core Knowledge

Question 2

*P71958RA0324* Turn over
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
Answer ALL questions.
The boxes show some physical quantities and their units.
Draw a straight line from each physical quantity to its correct unit.
One has been done for you.
Physical quantity Unit
velocity
force
power
moment
acceleration 		metre per second squared (m/s2)
watt (W)
newton (N)
metre per second (m/s)
newton metre (Nm)

Final answer

See diagram.

Physical quantity Unit velocity force power moment acceleration metre per second squared (m/s²) watt (W) newton (N) metre per second (m/s) newton metre (Nm)

Mark scheme points

  1. M1 One mark for any one correct connection, in addition to the given force–newton connection.
  2. M2 Two marks for two correct connections.
  3. M3 Three marks when all the connections are correct: velocity–m/s, power–W, moment–Nm and acceleration–m/s2.

Explanation

Match each quantity to the unit used to measure it:

  • Velocity is measured in metre per second, m/s.
  • Acceleration is measured in metre per second squared, m/s2.
  • Force is measured in newtons, N.
  • Power is measured in watts, W.
  • Moment is measured in newton metres, Nm.

The force–newton line has already been provided, so the four remaining lines must be drawn accurately.

Common mistakes

  • Do not use m/s for acceleration; acceleration requires the squared time unit, m/s2.
  • Do not confuse a moment, measured in Nm, with force, measured in N.
  • Power is measured in watts (W), not newtons or joules.
  • Most candidates scored full marks, but the reported errors mainly involved the units of acceleration and moments; the unit of power was the best known.

Practise Forces and motion units questions

Build a focused practice set from this part of the Edexcel IGCSE Physics syllabus.

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