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ERIC Number: EJ1148872
Record Type: Journal
Publication Date: 2017-Jun
Pages: 10
Abstractor: As Provided
ISSN: ISSN-1449-6313
Weight, the Normal Force and Newton's Third Law: Dislodging a Deeply Embedded Misconception
Low, David; Wilson, Kate
Teaching Science, v63 n2 p17-26 Jun 2017
On entry to university, high-achieving physics students from all across Australia struggle to identify Newton's third law force pairs. In particular, less than one in ten can correctly identify the Newton's third law reaction pair to the weight of (gravitational force acting on) an object. Most students incorrectly identify the normal force on the object as the third law force pair to weight, rather than the gravitational force of the object on the Earth. This misconception may be constructed by students during instruction on Newton's second law, and hence forms a logical, connected part of their knowledge structures, making it highly resistant to both traditional and more interactive instruction. The use of operational definitions of weight may contribute to this problem. We have addressed this issue by using a consistent and explicit definition of weight, and having students work through a short hands-on group activity using a bathroom scale and drawing free-body diagrams. As a result, the majority of students, post instruction, can correctly answer this question (and similar ones); and they retain this learning beyond the end of semester. This teaching strategy and activity could easily be used in high schools, so that students develop consistent knowledge frameworks when first introduced to Newton's laws.
Australian Science Teachers Association. P.O. Box 334, Deakin West, ACT 2600, Australia. Tel: +61-02-6282-9377; Fax: +61-02-6282-9477; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive; Guides - Classroom - Teacher
Education Level: Higher Education; Postsecondary Education
Audience: Teachers
Language: English
Sponsor: N/A
Authoring Institution: N/A
Identifiers - Location: Australia
Grant or Contract Numbers: N/A