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

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

Method

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