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Understanding velocity in one dimension

Understanding velocity in one dimension. David Trowbridge & Lillian McDermott University of Washington, Seattle. Success Factors in Science. Interpreting reality Hypothesizing and deductive reasoning Ability to discriminate between different but related concepts ( Distance vs Velocity).

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Understanding velocity in one dimension

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  1. Understanding velocity in one dimension David Trowbridge & Lillian McDermott University of Washington, Seattle

  2. Success Factors in Science • Interpreting reality • Hypothesizing and deductive reasoning • Ability to discriminate between different but related concepts ( Distance vs Velocity)

  3. Criterion to assess the understanding of velocity • Being ABLE (or not!!!!!) to interpret SIMPLEMOTIONS of real objects

  4. Assessment Methods • Piagetian motion tasks – presented no challenge • Students Interviews: • More quantitative version of interviews – revealed difficulties • Speed Comparison tasks – revealed confusion between distance and velocity • Written questions – confirmed the confusion between distance and velocity

  5. Uniform motion Problem: A train is traveling with a uniform velocity of 45 cm in 1.5 sec. How FAR!!!! did the train travel in 2.5 s ? Students’ typical answer: 45 cm for 1 ½ s … 22 cm for ¾ s (right??) I need one more sec... 11cm as I quartered it again… 45 + 22 + 11 = 78 cm WRONG Answer!!!!! More quantitative students interviews

  6. PROBLEM DETECTED by the more quantitative version of interviews • Looking @ speeds as distances covered by time and having 2 different sets of numbers • One for distances • Another for times

  7. Tasks that accompanied students’ interviews • Speed Comparison Task 1 (see graphs) • Speed Comparison Task 2 (see graphs)

  8. PROBLEM DETECTED(Speed comparison interviews) • Students associate same position with same velocity • Students associate being ahead as having more speed • Problems in accepting the concept of instantaneous velocity

  9. Success (%)Prior/Post to Instruction: • In-service elementary teachers 41 / ???? • Academically disadvantaged students 53/90 • General Physics students (SPS) 59/73 • Calculus Physics students 68/92

  10. Instructional Strategies for Success • Regular dialogue with students addressed the difference between Position @ Velocity • Daily work helped to clarify the distinction • Labs designed to address conceptual difficulties • Assessments also referred to this issue

  11. Notes • Acquisition of physical concepts strongly depend on the building of satisfactory connections between new concepts and students’ experiences. (Reformulation of students’ schemata) • Technical words used by students often did not always correspond to an understanding of how they relate to reality. • The precise use of vocabulary is a consequence of a better understanding of physical concepts. • GRADING In a Physics Course does not necessarily correspond to the level of conceptual understanding achieved by students!!!!!

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