Twigger et al., 1994

This UK-based research aimed to identify students’ prior conceptions of forces and motion by presenting students with a range of scenarios including horizontal motion, impulsive forces, constant horizontal motion, friction, accelerated motion, free-fall motion (with air resistance) and projectile motion.


  • Teachers should help students develop a “Newtonian perspective” of forces, recognising the need for unbalanced force in acceleration.
  • The analysis of motion should be broken down, looking at each phase, in turn, to see when forces are balanced and when they are not.
  • Students tend not to differentiate applied force from the 'force in a moving object' (similar to a physicist's concept of momentum). 
  • It may be beneficial to introduce the concept of momentum earlier in the course in order to help differentiate between forces and motion.
  • Computer-based simulations can help students picture forces during motion.

Learners’ ideas

  • Students tend to conflate the terms energy and force, regardless of age.
  • Many students identified an object which is moving as having energy, but far fewer could associate energy with a position (e.g. gravitational potential energy).
  • Some students explained slowing or stopping in terms of “running out of energy”.
  • Students were unable to clearly link frictional forces to the slowing of objects, instead using ideas such as “running out of energy” instead.
  • Students commonly describe the need for a continuous unbalanced force on a moving object for it to continue to move at a steady speed. They believed that a constant force would lead to a constant speed in most scenarios.
  • Many students could not describe the changing forces and their effects on a parachutist during the different phases of a skydive.
  • Older students were more likely to correctly describe motion, and link this to balanced and unbalanced force, when graphs were used.

Study Structure


The study aimed to:

  • Identify common prior conceptions in the reasoning of students aged 10-15 about horizontal and vertical motion.
  • Explore the extent to which their prior conceptions are age dependent.

Evidence collection

The study gathered evidence from hour-long, paired audiotaped interviews where students discussed forces and object motion across seven scenarios, giving individual responses. Transcribed audiotapes were coded using a devised scheme based on various responses. The research delved into students' task descriptions, explanations, and force categorization through numerical analysis. Researchers identified frequently occurring reasoning patterns.

Details of the sample

The sample consists of 36 students (16 girls, 20 boys) aged between 10 and 15 years.

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