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1.1.3Forces and Motion

Core Practical- Investigating Motion — Edexcel International GCSE Science Double Award 4SD0 - Physics Revision Notes & Topical Questions

5 min read 5 parts Lesson 5 of 26

📚 Edexcel International GCSE Science Double Award 4SD0 - Physics Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
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Part 1 of 5Variables and Equipment

Planning the variables correctly makes the results valid and easy to interpret.

Independent variable
  • Independent variable The distance fallen by the object, which the experimenter sets deliberately.
Dependent variable
  • Dependent variable The time taken for the object to fall, which is measured for each distance.
Control variables
  • Control variables Factors kept the same, such as using the same falling object and dropping it from rest.
Measuring equipment
  • Measuring equipment A metre rule or tape measure for distance and a stopwatch or light gate for time.

Part 2 of 5Method

Repeat each measurement so that an average time can be found.

1
Measure a set height using a metre rule, and record it as the distance fallen.
2
Release the object from rest at that height and start the timer at the moment of release.
3
Stop the timer when the object lands, and record the time taken for the fall.
4
Repeat the timing three times at the same height to find a reliable average time.
5
Repeat for several heights, then calculate the average speed = distance ÷ average time.

Part 3 of 5Improving the Accuracy

Improving the Accuracy
Reaction time
  • Reaction time Starting and stopping a handheld stopwatch causes an error of about 0.2 to 0.25 s, which matters for short falls.
Light gates
  • Light gates Light gates start and stop timing automatically, which removes most of the reaction time error.
Parallax error
  • Parallax error Reading the metre rule from an angle gives a wrong height, so read it at eye level.
Draughts
  • Draughts Air movement can change the motion of a light falling object, so the test should be done in still air.

Part 4 of 5Worked Example

Question

  • A paper cone is dropped from a height of 1.6 m.
  • Three timings are 1.02 s, 1.04 s and 1.00 s.
  • Calculate the average speed.

  1. Average time = (1.02 + 1.04 + 1.00) ÷ 3 = 1.02 s.
  2. Average speed = distance ÷ average time = 1.6 m ÷ 1.02 s.
  3. Average speed ≈ 1.57 m/s.

Answer The average speed of the paper cone is about 1.57 m/s.

Part 5 of 5Exam Checklist & Tips

1.1.3 – Key Points for the Exam

  • Independent variable The variable that the experimenter deliberately changes.
  • Dependent variable The variable that is measured as a result of the change.
  • Control variable A variable that is kept constant so that it does not affect the results.
  • Reaction time error A systematic error caused by the delay between seeing an event and pressing the stopwatch.
  • Light gate An electronic sensor that starts and stops a timer when an object breaks a beam of light.
  • Parallax error An error in reading a scale caused by viewing it from an angle instead of straight on.

Common Mistakes

  • Recording only one timing per height; averages of repeated readings are more reliable and should be used.
  • Calculating average speed as an average of individual speeds instead of total distance divided by average time.
  • Describing the object as accelerating from the single speed value;
    • the experiment measures average speed only.
  • Blaming random error for a consistent bias; a constant reaction-time delay is a systematic error.

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Physics 0625 & 9702 SUVAT Mastery Graph Interpretation

Constant Acceleration Equations (SUVAT) & Slopes

v = u + at  |  s = ut + ½at2  |  v2 = u2 + 2as  |  s = ½(u + v)t

  • Displacement-Time Graph: Gradient = Velocity (curve = accelerating).
  • Velocity-Time Graph: Gradient = Acceleration; Area under curve = Distance travelled / Displacement.
  • Free Fall in vacuum: a = g ≈ 9.81 m/s2 downwards (air resistance negligible).
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