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Talking About Forces

Each of the first four volumes provides 25 probes with easy-to-follow steps for uncovering and addressing students’ ideas by promoting learning through conceptual change instruction. Probes cover topics such as physical, life, and Earth and space science; the nature of science; and unifying themes. Each volume on page 23 provides topic-specific probes. These invaluable books include teacher materials that explain content, identify links to standards, and suggest grade-appropriate ways to present materials so students learn the concepts accurately. Teachers, professional development coordinators, and college science and preservice faculty will find these resources essential and exciting.

Talking About Forces

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Purpose

The purpose of this assessment probe is to elicit beginning ideas about forces. The probe is designed to reveal whether students generally identify forces as pushes and pulls.

Related Concepts

Pushes and pulls

Explanation

Yolanda has the best answer: “I think a force is either a push or a pull.” By basic definition, a force is a push or pull. Some students might think there is a third type of force, which they sometimes refer to as a “holding force”; it is different from a push or pull and “holds” resting objects in place. For example, they might think that a book resting on a table is being neither pulled on nor pushed. In this instance, the pulling force (gravity) and the pushing force (the upward force exerted by the table on the book) are balanced.

Administering the Probe

This probe is best used at the elementary and middle school levels, although it may be useful in determining whether high school students still believe in a “holding force.” Young children are just beginning to learn about forces, and so this probe is particularly helpful because it introduces them to “push and pull” vocabulary as a prerequisite to describing how forces affect motion. With very young children, who may not be ready to understand how an object at rest is affected by forces, you might consider eliminating the last distracter (Violet’s response).

Related Ideas in National Science Education Standards (NRC 1996)

K–4 Position and Motion of Objects

  • The position and motion of objects can be changed by pushing or pulling. The size of the change is related to the strength of the push or pull.
Standards

K–2 Motion

  • The way to change how something is moving is to give it a push or a pull.

3–5 Motion

  • The earth’s gravity pulls any object toward it without touching it.
  • Without touching them, a magnet pulls on all things made of iron and either pushes or pulls on other magnets.
  • Without touching them, material that has been electrically charged pulls on all other materials and may either push or pull other charged materials.

Related Research

  • Younger students tend to bring lay meanings of the word force to their learning. They often associate the word force with coercion, living things, physical activity, and muscular strength (Driver et al. 1994).
  • Some students have difficulty associating manifestations of force with pushes or pulls (Shevlin 1989; Erickson and Hobbs 1978). For example, some primary-age children did not associate a kick or throw with a push. Students ages 6–14 thought there was a difference between forces that pull and those that just “hold” (Driver et al. 1994).
  • Many students widely regard rest as a natural state in which no forces act on an object (Minstrell 1982). Students who recognize there is some type of “holding force” that keeps an object stationary tend to think of it as quite different from a pushing or pulling force (Driver et al. 1994).

Suggestions for Instruction and Assessment

  • Take students on a “push and pull” walk. Identify all the examples of things they push or pull or see being pushed or pulled.
  • Present students with examples of forces and ask them to decide which examples are pulls and which are pushes. This can be done as a card sort activity.
  • Encourage students to come up with their own lists of pushes and pulls.
  • Younger students should first have opportunities to experience pushes and pulls with contact forces (a contact force is a force either between two objects or between an object and a surface that are in contact with each other). Later, when they develop the idea of forces that act at a distance, they can explore pushes and pulls with falling objects, magnets, and electrically charged objects.
  • Build a word wall of force- and motion related words. Include the words push and pull and encourage students to use these words when they describe forces and motions.
  • The forces that young children are most familiar with are the ones exerted by their own muscles. When introducing the notion of force as a push or pull, have children push and pull on objects using their own muscles. Then transition to discussing pushes and pulls exerted by other living things and nonliving objects so that the children don’t equate force with only human action.
  • Bridging analogies (Clement 1993) are useful with middle school students, who may have difficulty accepting the idea that an object at rest, such as a book on a table, has both a pushing and pulling force acting on it. A good bridging analogy would be to show the class a book resting on a spring and then a book resting on a springy surface like a piece of foam (Driver et al. 1994).
References

American Association for the Advancement of Science (AAAS). 1993. Benchmarks for science literacy. New York: Oxford University Press.

American Association for the Advancement of Science (AAAS). 2009. Benchmarks for science literacy online. www.project2061.org/publications/ bsl/online

Clement, J. 1993. Using bridging analogies and anchoring intuitions to deal with students’ preconceptions in physics. Journal of Research in Science Teaching 30 (10): 1241–1257.

Driver, R., A. Squires, P. Rushworth, and V. WoodRobinson. 1994. Making sense of secondary science: Research into children’s ideas. London: RoutledgeFalmer.

Erickson, G., and E. Hobbs. 1978. The developmental study of student beliefs about force concepts. Paper presented to the annual convention of the Canadian Society for the Study of Education. Ontario, Canada (June 2).

Minstrell, J. 1982. Explaining the “at rest” condition of an object. The Physics Teacher 20: 10–14.

National Research Council (NRC). 1996. National science education standards. Washington, DC: National Academies Press.

Shevlin, J. 1989. Children’s prior conceptions of force aged 5–11 and their relevance to attainment target 10 of the national curriculum of science. M.Ed. thesis, University of Leeds, UK.

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