P4 Explaining motion

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P4 Explaining motion
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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.

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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.)

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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.

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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.

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What could be easier?
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KS3 responses football
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KS4 responses football
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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)

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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

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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

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P4 part 2 (lessons 5- 6)

• Key ideas
• Average speed
• Instantaneous speed
• Velocity (as distinct from speed)
• Using graphs to represent motion

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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)

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P4 part 4 (lesson 11)

• Key idea
• Steady motion requires no (resultant) force

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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)

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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

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Practical work

• Exploring the origins of reaction forces
• Explosions speeds of the parts
• Exploring F Dt D(mv)
• Measuring work in different situations
• Speed of falling object after different distances
• (optional) Analysis of motion using video
  recordings

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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

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