P4 Explaining motion

1. P4 Explaining motion

2. GCSE Additional Science Ideas that: • are important from the perspective of the subject; • enable you to pursue the subject further; • give you a sense of what the subject is like, and how those who practice it think.

3. Explaining motion (1) The basic principle (or commitment): • The motion of any object can be explained by the forces acting on the object. (So only the idea of force should be used to explain motion.)

4. Explaining motion (2) The procedure: • Identify the object whose motion you are interested in. • Identify all the forces acting on this object, noting their directions. • Add the forces acting on the object to find the resultant force acting on it.

5. Explaining motion (3) The rules: • If there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force. • If the resultant force acting on an object is zero, its motion will not change.

6. What could be easier?

8. KS3 responses: football

9. KS4 responses: football

10. Structure of module P4 • Recognising and identifying forces acting in simple situations Building on knowledge that: - If object is stationary, forces add to zero - If forces do not add to zero, motion of object changes • Learning to describe motion more precisely • Linking force and change of momentum • Falling and rising (GPE and KE)

11. P4: part 1 (lessons 1- 4) Key ideas: • Forces arise from interactions • Always arise in pairs • Equal in size; opposite in direction • Each acts on a different object

12. P4: part 1 (lessons 1- 4) • identifying forces in basic situations (pushing, pulling, sitting, hanging) • saying clearly which object each acts on • recognising friction as an interaction - explaining forces in walking, vehicles moving • recognise, and explain origin of, the (normal) reaction force

13. P4: part 2 (lessons 5- 6) Key ideas: • Average speed • Instantaneous speed • Velocity (as distinct from speed) • Using graphs to represent motion

14. P4: part 3 (lessons 7- 9) Key ideas: • momentum • force x time for which it acts = change of momentum • F (Dt) = D (mv) • Application to road safety and collisions in sport • Forces in steady motion (F = 0) (the difficult case)

15. P4: part 4 (lesson 11) Key idea: • Steady motion requires no (resultant) force

16. P4: part 5 (lessons 11-12) Key ideas: • work = force x distance (in direction of force) • work done = energy transferred • Falling and rising: loss of GPE equals gain in KE (and vice versa)

17. ICT support • Video clips (of explosions, recoil, etc.) • Powerpoints (for introducing difficult ideas) • ‘Identifying forces’ animated task • Powerpoint: ‘Walking graphs’ • Multimedia Motion 2 • Video: Forces in cycling

18. Practical work • Exploring the origins of reaction forces • Explosions: speeds of the parts • Exploring FDt = D(mv) • Measuring work in different situations • Speed of falling object after different distances • (optional) Analysis of motion using video recordings

19. Whole class discussion • Very important in several lessons • Need to plan these carefully to get maximum benefit • Well supported by ICT resources, and activity sheets • Consider using written exercises for small-group discussion rather than as individual tasks