Core Practical 10: Investigating Collisions using ICT (Edexcel International A Level Physics)

Revision Note






Core Practical 10: Investigating Collisions using ICT

Aims of the Experiment

  • To investigate conservation of momentum in two directions
    • Considering if collisions are elastic
    • Constructing a diagram of 2D collisions
  • Use of ICT software is required
    • 'Tracker' is recommended by Edexcel

Equipment List

  • Small spheres
    • Of two different diameters (ball bearings are ideal)
  • Digital camera able to record video
    • Support to allow it to be positioned directly above the collision
  • Computer with Tracker installed
  • 30 cm ruler
  • Micrometer or calipers
  • Balance
  • Graph paper



1. Measure the mass of the spheres using the balance and record

2. Measure the diameter of the spheres using a micrometer or Vernier calipers

3. Mark an approximately central point on the graph paper

    • This will be where the stationary sphere is placed

4. Start the camera recording

5. Within the area of the graph paper, roll a sphere into the stationary one

6. Replace the stationary sphere in its initial place and repeat the experiment up to three times

    • A slightly different angle of approach should be used for each collision

7. Download the video file from the camera to the computer that runs Tracker 

    • Load the clip into the program.

Analysing the Results

  • Use Tracker to analyse the video clips.
    • Input the mass and diameter of each sphere when prompted
    • Use the ‘velocity overlay’ feature so that the software can analyse velocities
  • The Tracker software allows for frame-by-frame analysis of the movement of the spheres
    • Orientate the axes to make the velocity of the moving ball along one of the axes
    • Record the momentum of each ball as indicated in Tracker


  • Construct a vector diagram from the results


Evaluating the Experiment

  • ICT is used in this experiment because
    • The events happen to swiftly for the unaided eye to take readings
    • ICT generally provides more precise and reliable data 

Systematic errors:

  • Parallax error from camera to the table
  • The precision of the balance may give a wide range of possible values for mass
    • If possible use a more precise balance
  • The spheres may have damage
    • Check there is no damage to the surface of each sphere before using
  • The Tracker axes may not be correctly aligned when analysing

Random errors:

  • The collision event may happen between frames
  • From variations in the table surface
    • This could cause loss or gain of kinetic energy due to friction or slopes
  • The sphere may not travel far enough to hit the second stationary sphere
    • Discard this result and release with greater initial velocity

Exam Tip

It can be helpful to practice a few collisions before making your final readings. This will help you become familiar with how fast to release the sphere.

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Author: Joanna

Joanna obtained her undergraduate degree in Natural Sciences from Cambridge University and completed her MSc in Education at Loughborough University. After a decade of teaching and leading the physics department in a high-performing academic school, Joanna now mentors new teachers and is currently studying part-time for her PhD at Leicester University. Her passions are helping students and learning about cool physics, so creating brilliant resources to help with exam preparation is her dream job!