## 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.

#### Suggestions

• 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

#### Aims

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.