Learning to Think About Gravity Misconceptions Claudine Kavanagh Esther Zirbel Tufts University
Jan 06, 2018
Learning to Think About Gravity
Misconceptions
Claudine Kavanagh Esther Zirbel
Tufts University
Thinking about gravity
1. History and Gravity as a Force
2. “Misconceptions”3. Effective instruction
History of gravity
Aristotle: 4 elements, 2 domains. Gravity is not a force.
Newton: Gravity = force across entire universe.
Einstein: Space tells matter how to move. Matter tells space how to curve. Gravity is not a force.
2) “Misconceptions”
Is there gravity in space? (Think/pair/share)
Equivalence PrincipleWhy are these people weightless?(Think/pair/share)
Learning gravity? Easy! Right?!
Viennot (1979): University of ParisTested undergraduates’ conceptual understanding of projectile motion
Most students drew arrows in the direction(s) of motion
Students’ ideas were identical to pre-Newtonian “impetus” taught at the same university 600 years earlier by John Buridan
Misconceptions: Free Fall
1) Things fall if not supported 2) Strength and effort prevent
falling3) Gravity is not a force4) Heavier objects fall faster5) Gravity acts only on heavy,
slow, inactive objects6) Gravity acts upwards on a
falling object
Misconceptions: Projectile Motion1) Motion implies a force in the
direction of motion2) Objects fall straight down if not
supported (inverted L)3) Impetus may wear out/ be overcome4) Living or active things impart
impetus5) Projectiles continue to
accelerate after release
Misconceptions: OrbitsGravity needs airThere is no gravity in spaceObjects in orbit are weightless, so gravity does not affect them
The force of gravity diminishes with increasing altitude
Force is needed to keep an object in orbitPlanets closer to the sun (or with fast spin) have more gravity
Gravitational attraction between objects is not equal and opposite
Misconceptions Summary
Few graduates-including those with top grades- understand the foundational concept of gravity.
What does everyday experience contribute to students’ understanding of gravity?
Chapter 3: Effective instruction
What are students expected to learn? National Science Education Standards K-5: Magnetism (action-at-a-distance).
6-8: Falling motion, projectile motion and orbits. Gravity is “a ubiquitous force that holds the universe together”
9-12: Newton’s laws & calculations of gravitational force. Three theoretical issues:
Universal gravitation Massive structures in the Universe General relativity (historical only)
Teaching: What works? Hynd, Alvermann & Qian (1997) studied 73 pre-service teachers learning about gravity & projectile motion
All participants “non-Newtonian” on pre-test Different intervention methods: what worked?
Only 2 participants converted to Newtonian explanation
Same 2 had been predisposed to scientific “frame of mind”!
“personal motivation” “tendency to view scientific information as useful”
Teaching: What works?
Prescott: two “intervention” teachers & two “control” teachers.
Intervention taught gravity qualitatively first, then quantitatively
“The most significant factor determining whether student misconceptions were eliminated was found to be the teachers’ ability to deal with their own misconceptions” (Prescott, 2004)
Teaching: What works?
How would you answer this question?(Think/pair/share)Smith & Peacock (1992) identified two apparent contradictions in teaching gravity: 1. “Heavier things” experience greater attraction, yet accelerate at the same rate as “lighter things”
2. “Light objects” fall at a constant rate
More research?
No data found: Elliptical orbits Universal applicability of same physical laws
Large scale structure seen in the U today
Einstein’s general theory of relativity
Equivalence principle
Anti-gravity research here at Tufts?
Thank you!Q&A?