Dealing with misconceptions /alternative conceptions

1. NQT Conference The Royal School of Mines 14th July 2014Teaching forces - common misconceptions and ideas for teachingLiz Hutchins

3. Dealing with misconceptions /alternative conceptions 1 in 7 people believe that the Periodic table is arranged alphabetically

4. Some features of misconceptions : • linked to everyday use of language; • constructed from everyday experience and are usually adequate for everyday life; • explain how the world works in simple terms; • often similar to earlier scientific models; •may be inconsistent with science taught in schools; • can be resistant to change; • may inhibit further conceptual development. “A misconception can be defined as a view that does not fully coincide with the scientific view.”

5. You may have heard….? • ‘I am going to weigh myself’ (everyday language) • ‘Forces make things move.’ (similar to earlier scientific model) • ‘Astronauts float because there is no gravity in space.’ (simple explanation) • Others? Barriers to learning

6. Identifying pupil misconceptions • Use true /false sheet or card sort activity • Use a questionnaire/diagnostic questions e.g. (SPT) • Through experiment

7. Question What do you think about science? For each of the statements below, show whether you Agree Disagree Not sure • To keep an object moving a force must be kept on it. • Objects stop moving when their force runs out.

8. Using sort cards The cards show statements made by pupils. Decide if the statement is “on the right lines” or “on the wrong track” For those you identify as “on the wrong track” is a misconception is involved?

11. Diagnostic questions Which misconceptions are being addressed by these questions? ForcesAWayOfLookingAtTheWorld.pdf

12. http://www.physicsclassroom.com

13. Some very common misconceptions • Only animate objects can exert a force (a table can’t push on a book) • Mass and weight are the same thing • Force is a property of an object • If an object is moving there must be a force acting on it • If an object is stationary there are no forces acting on it • Heavy things fall faster than light things

14. Changing ideas Early idea “all objects have a natural tendency to stop moving” If friction were eliminated a ball on a curved track would continue to rise to the same height - Galileo Forces do not cause motion they cause acceleration – Newton

15. Using models to help reduce misconceptions • Forces – cardboard arrows Why? • Making forces explicit • Can be applied at all levels (year 7 to A Level) • Allows an “at a glance view” of pupil understanding

16. How we get free body diagrams - Representing forces - A butterfly

17. ..and simplified Support force from leaf Support force from leaf butterfly Gravitational force from Earth Gravitational force from Earth

18. Free body diagram Support force from leaf butterfly Gravitational force from Earth Gravitational force from Earth

19. http://www.physicsclassroom.com/

20. Confusion between resultant forces acting on an object and Newton’s 3rd law pairs • Pairs of forces act between different objects • They are the same type of force • They act for the same time. • They act in opposite directions • They are the same size (magnitude) • E.g The gravitational pull of the earth on you is the same size as the gravitational pull of you on the earth

21. Confusion between resultant forces acting on an object and Newton’s 3rd law pairs Only use the forces that are acting on one objectwhen you work out the resultant force. Here the resultant force is zero because the weight of the girl is equal to the support force from the springboard. The forces are balanced.

22. Linking misconceptions to possible solutions • Mass/weight – experiments with Kg and Newton scales, reference to language • Force needed to continue motion- low friction experiments, hovercraft, air track • Effects of air resistance – experiment with dropping objects • Surfaces cannot exert a force – microscopic view, experiments with compressing foam and masses • Forces can change direction – experiment with marbles and straws • Forces cause acceleration – experiment with trolley and string, tug of war

23. Experiments and demos summary Using arrows – free body diagrams Using arrows – 3rd Law pairs Balanced and unbalanced forces – cutting the string Marbles and straws to change motion Stretching and squashing – foam, board and springs Falling objects – paper, paper and book (Marvin and Milo), identical balls Reducing friction - hovercraft Card, weight and cup Marvin and Milo experiments

24. Using Marvin and milo Cartoons Gripping rice– balanced forces, pupils may think there are no forces acting on an object, when it is not moving On a roll – forces can act at a distance, pupils may think that objects have to be touching to exert a force. Dare devil egg (object) – inertia, pupils may think the card and the cylinder will have the same acceleration Book launch– the effect of air resistance, pupils may think the paper falls more slowly in air because it is lighter than the book. Slinky Drop– forces on a falling object, pupils may think the coils at the top and bottom of the slinky have the same forces acting on them

25. References • http://www.nationalstemcentre.org.uk/elibrary/resource/7415/understanding-misconceptions • http://listverse.com/2009/04/08/top-10-ridiculously-common-science-myths/

26. Teaching and learning challenges from SPT (supporting physics teaching) • PN physics narrative • TL teaching and learning challenges • TA teaching approaches • http://supportingphysicsteaching.net/FoHome.html • http://supportingphysicsteaching.net/FmHome.html

27. Finding Resourceswww.talkphysics.orgwww.iop.orgwww.physics.org

28. Using force arrows Use the arrows to illustrate the forces acting on a cup when …. It rests on a table It is suspended from a rubber band It is suspended from a rubber band and pulled down (stationary) It is lifted up (accelerating) Is suspended from the centre of a string held at two different angles

29. Using force arrows Use the arrows to illustrate the forces acting on a person in a lift when …. It is stationary on Level 1 It is accelerating upwards It is travels at a steady speed between Levels 1 and 2 It decelerates as it reaches Level 2 The doors open on Level 2

30. Using force arrows Use the arrows to illustrate the forces acting on a marble travelling at constant speed on a vertical circular track when …. It is stationary at the top of the ramp It travels at constant speed down the ramp It is at the bottom of the loop It is at the side of the loop It is at the top of the loop

31. Using force arrows Use the arrows to illustrate the Newton’s third law pairs when …. A book rests on the table You carry a shopping bag You drop some keys You deflate a balloon

32. Short demos/ experiments • Drop two balls of identical size but different masses from the same height (record the sound or film it) • Change the speed or direction of marbles by blowing through straws. • Two people pull with the same force on a toy car, one person lets go, what happens?

33. Ideas for short experiments and demos What happens when you drop the spring? • The whole spring falls at once • The bottom coil does not start to fall initially What happens when you drop the “groan tube”? • You only hear the sound when the tube stops falling • You hear the sound all continuously as it falls What happens when the spoon is balanced? • There is the same weight on both sides at the balance point • The weight on either side will be different