2. Jan Roscoe Publications AQA Examinations AS and A Level Physical Education AS / A year 1 (A1) AS 7581 Section 3.1 Factors affecting participation in physical activity and sport 3.1.5 Biomechanical movement 3.1.5.1 Biomechanical principles

3. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 2 3.1.5 Biomechanical movementINDEX 33NEWTON’s LAWS OF MOTION 3 44NEWTON’s FIRST LAW OF MOTION 4 77NEWTON’s FIRST LAW OF MOTION - THE EFFECT OF FORCES 7 88NEWTON’s SECOND LAW OF MOTION 8 1111NEWTON’s THIRD LAW OF MOTION 11 1515EXAMPLES OF NEWTON’s THIRD LAW 15 2121REACTION 21 2222DISTANCE 22 2323DISTANCE - DISPLACEMENT 23 2424POSITION 24 2525SPEED - VELOCITY 25 2626CENTRE OF MASS (GRAVITY) 26 2929BALANCE and TOPPLING 29 3131BALANCE and TOPPLING - STABILITY and TOPPLING 31 3333BALANCE and TOPPLING - FACTORS AFFECTING STABILITY 33 3434BALANCE and TOPPLING 34

4. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 3 3.1.5 Biomechanical movement NEWTON’s LAWS OF MOTION

5. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 4 3.1.5 Biomechanical movement NEWTON’s FIRST LAW OF MOTION NEWTON’S FIRST LAW this law is used when zero net force is applied to an object this law is used when zero net force is applied to an object this doesn’t mean that zero force acts, but that all forces must cancel out this doesn’t mean that zero force acts, but that all forces must cancel out

6. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 5 3.1.5 Biomechanical movement NEWTON’s FIRST LAW OF MOTION NEWTON’S FIRST LAW with zero net force an object with zero net force an object –is stationary or –moves at constant speed in the same direction for the sprinter, horizontal forces cancel out for the sprinter, horizontal forces cancel out and vertical forces cancel out and vertical forces cancel out hence he or she travels at constant speed hence he or she travels at constant speed

7. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 6 3.1.5 Biomechanical movement NEWTON’s FIRST LAW OF MOTION NEWTON’S FIRST LAW examples: examples: –a sprinter running at constant speed –a cyclist going at constant speed –a swimmer swimming at constant speed –any vehicle going at constant speed –any sportsperson standing still

8. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 7 3.1.5 Biomechanical movement NEWTON’s FIRST LAW OF MOTION THE EFFECT OF FORCES this law does not mean that there are no forces this law does not mean that there are no forces very large forces can act very large forces can act but if the object is going at constant speed but if the object is going at constant speed these forces MUST cancel out these forces MUST cancel out for the sprinter, vertical arrows are the same size and therefore cancel out for the sprinter, vertical arrows are the same size and therefore cancel out horizontal forces are the same size and therefore also cancel out horizontal forces are the same size and therefore also cancel out NEWTON’S FIRST LAW

9. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 8 3.1.5 Biomechanical movement NEWTON’s SECOND LAW OF MOTION NEWTON’S SECOND LAW this law is used when a NET FORCE acts on an object this law is used when a NET FORCE acts on an object net force forwards produces acceleration - positive net force forwards produces acceleration - positive net force backwards produces deceleration - negative net force backwards produces deceleration - negative net force sideways produces change of direction net force sideways produces change of direction

10. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 9 3.1.5 Biomechanical movement NEWTON’s SECOND LAW OF MOTION FORMULA force = mass x acceleration force = mass x acceleration F = m x a F = m x a hence the bigger the force the bigger the acceleration hence the bigger the force the bigger the acceleration the bigger the mass, the smaller the acceleration the bigger the mass, the smaller the acceleration NEWTON’S SECOND LAW

11. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 10 3.1.5 Biomechanical movement NEWTON’s SECOND LAW OF MOTION THE SPRINTER four forces are acting four forces are acting upwards force = downwards force upwards force = downwards force net horizontal forces act backwards net horizontal forces act backwards therefore there is no upward acceleration therefore there is no upward acceleration the sprinter runs horizontally the sprinter runs horizontally there is a net backwards force there is a net backwards force producing a negative acceleration producing a negative acceleration or deceleration or deceleration

12. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 11 3.1.5 Biomechanical movement NEWTON’s THIRD LAW OF MOTION NEWTON’S THIRD LAW this law is used when two bodies exert forces on one another this law is used when two bodies exert forces on one another action and reaction are equal and opposite in direction action and reaction are equal and opposite in direction Helen Roscoe Photography

13. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 12 3.1.5 Biomechanical movement NEWTON’s THIRD LAW OF MOTION NEWTON’S THIRD LAW action of jumper down on ground (force in black) action of jumper down on ground (force in black) = reaction of ground up on jumper (force in red) = reaction of ground up on jumper (force in red) the harder you push down on the ground, the more the ground pushes up on you the harder you push down on the ground, the more the ground pushes up on you

14. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 13 3.1.5 Biomechanical movement NEWTON’s THIRD LAW OF MOTION APPLICATIONS at the swim start - the swimmer pushes back on the blocks as hard as possible at the swim start - the swimmer pushes back on the blocks as hard as possible the blocks push forward - and provides forward acceleration - on the swimmer the blocks push forward - and provides forward acceleration - on the swimmer Helen Roscoe Photography

15. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 14 3.1.5 Biomechanical movement NEWTON’s THIRD LAW OF MOTION APPLICATIONS a swimmer drives backwards on water with hands and feet (force in black) a swimmer drives backwards on water with hands and feet (force in black) the water pushes the swimmer forward (force in red) the water pushes the swimmer forward (force in red)

16. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 15 3.1.5 Biomechanical movement EXAMPLES OF NEWTON’s THIRD LAW REACTION FORCES are forces acting via Newton’s Third Law are forces acting via Newton’s Third Law when one object pushes on another, the first object experiences a force equal but opposite in direction to the second when one object pushes on another, the first object experiences a force equal but opposite in direction to the second jumper pushes down on the ground, ground pushes up on the jumper jumper pushes down on the ground, ground pushes up on the jumper

17. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 16 3.1.5 Biomechanical movement EXAMPLES OF NEWTON’s THIRD LAW REACTION FORCES are forces acting via Newton’s Third Law are forces acting via Newton’s Third Law when one object pushes on another, the first object experiences a force equal but opposite in direction to the second when one object pushes on another, the first object experiences a force equal but opposite in direction to the second weight lifter pulls up on weight, weight pulls down on lifter weight lifter pulls up on weight, weight pulls down on lifter

18. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 17 3.1.5 Biomechanical movement EXAMPLES OF NEWTON’s THIRD LAW REACTION FORCES swimmer pushes backwards on the water swimmer pushes backwards on the water reaction force thrusts the swimmer forward reaction force thrusts the swimmer forward

19. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 18 3.1.5 Biomechanical movement EXAMPLES OF NEWTON’s THIRD LAW REACTION FORCES canoeist pushes backwards on the water canoeist pushes backwards on the water reaction force thrusts the canoe forward reaction force thrusts the canoe forward

20. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 19 3.1.5 Biomechanical movement EXAMPLES OF NEWTON’s THIRD LAW REACTION FORCES sprinter pushes back and down on the ground sprinter pushes back and down on the ground the ground pushes upwards and forwards on the sprinter the ground pushes upwards and forwards on the sprinter

21. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 20 3.1.5 Biomechanical movement EXAMPLES OF NEWTON’s THIRD LAW REACTION FORCES in cycling, the tyre on the rear wheel pushes backward on the ground in cycling, the tyre on the rear wheel pushes backward on the ground the ground pushes forward on the rear wheel the ground pushes forward on the rear wheel

22. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 21 3.1.5 Biomechanical movementREACTION INTERNAL FORCES are exerted on both origin and insertion of a muscle. are exerted on both origin and insertion of a muscle. the force on the insertion is a reaction to the force on the origin the force on the insertion is a reaction to the force on the origin force on origin pulls bone H to the right force on origin pulls bone H to the right force on insertion pulls bone U to the left force on insertion pulls bone U to the left the two forces are equal in size but opposite in direction the two forces are equal in size but opposite in direction

23. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 22 3.1.5 Biomechanical movementDISTANCE DISTANCE means the total path length moved by a body means the total path length moved by a body example: example: –a 10,000 m race is run round and round the track –25 times 400 m, starting and finishing POSITION are the same –distance travelled is 10,000 m unit the metre m unit the metre m

24. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 23 3.1.5 Biomechanical movement DISTANCE - DISPLACEMENT DISPLACEMENT this means the vector distance from a fixed point (starting point or origin) this means the vector distance from a fixed point (starting point or origin) the actual ‘as the crow flies’ distance between start and finish (with direction included) the actual ‘as the crow flies’ distance between start and finish (with direction included) example: example: –the start and finish of a long distance race (stage 5 of the Tours de France) –may be 190 km apart due West, but the distance travelled may be 250 km! unit the metre m unit the metre m

25. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 24 3.1.5 Biomechanical movementPOSITION POSITION a way of explaining where a point is relative to some fixed point a way of explaining where a point is relative to some fixed point position is usually expressed in terms of coordinates (x and y) like a graph in maths position is usually expressed in terms of coordinates (x and y) like a graph in maths example: example: –the centre forward takes a shot from a position 20 m out from the goal line, and 10m to the left of the left hand post –the left hand post is the fixed point or origin of measurement –20 m and 10 m are the coordinates of the position of the centre forward relative to that point.

26. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 25 3.1.5 Biomechanical movement SPEED - VELOCITY SPEED = distance moved v = s unit ms -1 time taken t = distance moved v = s unit ms -1 time taken t = scalar (no direction) = scalar (no direction) = distance moved in 1 second = distance moved in 1 secondVELOCITY = speed in a given direction = speed in a given direction = vector = vector DISTANCE / TIME graph gradient of graph is velocity gradient of graph is velocity

27. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 26 3.1.5 Biomechanical movement CENTRE OF MASS (GRAVITY) CENTRE of MASS (CoM) this is the scientific term for centre of gravity - since the concept is not dependent on gravity this is the scientific term for centre of gravity - since the concept is not dependent on gravity CoM is the single point in a body which represents all the spread out mass of a body CoM is the single point in a body which represents all the spread out mass of a body the weight acts at the CoM since gravity acts on mass to produce weight the weight acts at the CoM since gravity acts on mass to produce weight

28. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 27 3.1.5 Biomechanical movement CENTRE OF MASS (GRAVITY) WHERE IS THE CENTRE OF MASS? position of centre of mass depends on shape of body position of centre of mass depends on shape of body this is how the high jumper can have his CoM pass under the bar this is how the high jumper can have his CoM pass under the bar but he could still clear the bar but he could still clear the bar

29. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 28 3.1.5 Biomechanical movement CENTRE OF MASS (GRAVITY) WHERE IS THE CENTRE OF MASS? note the position of this person’s centre of mass (red dot) note the position of this person’s centre of mass (red dot) Helen Roscoe Photography

30. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 29 3.1.5 Biomechanical movement BALANCE and TOPPLING BALANCE to keep on balance the CoM must be over the base of support to keep on balance the CoM must be over the base of support

31. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 30 3.1.5 Biomechanical movement BALANCE and TOPPLING TOPPLING the CoM must be over the base of support if a person is to be on balance the CoM must be over the base of support if a person is to be on balance toppling would be caused by the weight acting at the CoM creating a moment about the near edge of the base of support toppling would be caused by the weight acting at the CoM creating a moment about the near edge of the base of support this can be used by divers or gymnasts to initiate a controlled spinning (twisting) fall and lead into somersaults or twists this can be used by divers or gymnasts to initiate a controlled spinning (twisting) fall and lead into somersaults or twists

32. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 31 3.1.5 Biomechanical movement BALANCE and TOPPLING STABILITY and TOPPLING the CoM must be over the base of support if a person is to be on balance the CoM must be over the base of support if a person is to be on balance so a person holding a balance is said to be in equilibrium so a person holding a balance is said to be in equilibrium like a person holding a handstand like a person holding a handstand this is an unstable equilibrium because a very small force could cause the CoM to move enough to topple the person this is an unstable equilibrium because a very small force could cause the CoM to move enough to topple the person Helen Roscoe Photography

33. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 32 3.1.5 Biomechanical movement BALANCE and TOPPLING STABILITY and TOPPLING the CoM must be over the base of support if a person is to be on balance the CoM must be over the base of support if a person is to be on balance so a ball sitting on the floor can be said to be in equilibrium – in this case neutral equilibrium – since a small sideways force will cause the ball to move, but remain in equilibrium – still stable to toppling so a ball sitting on the floor can be said to be in equilibrium – in this case neutral equilibrium – since a small sideways force will cause the ball to move, but remain in equilibrium – still stable to toppling as is a gymnast lying on the floor! as is a gymnast lying on the floor!

34. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 33 3.1.5 Biomechanical movement BALANCE and TOPPLING FACTORS AFFECTING STABILITY the CoM must be over the base of support if a person is to be stable the CoM must be over the base of support if a person is to be stable hence the bigger the area of the base of support, the further the CoM would have to be moved to make the situation unstable (would topple) hence the bigger the area of the base of support, the further the CoM would have to be moved to make the situation unstable (would topple) so for a rugby player receiving a tackle, he would be more stable if his / her feet were as wide apart as possible so for a rugby player receiving a tackle, he would be more stable if his / her feet were as wide apart as possible also, the higher the CoM, the less stable a person would be, so the rugby player would crouch low to lower his / her CoM to make his / her situation more stable also, the higher the CoM, the less stable a person would be, so the rugby player would crouch low to lower his / her CoM to make his / her situation more stable

35. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 34 3.1.5 Biomechanical movement BALANCE and TOPPLING STABILITY and TOPPLING the CoM must be over the base of support if a person is to be on balance the CoM must be over the base of support if a person is to be on balance so a beam gymnast will need careful control of the position of her CoM if she is not to fall off so a beam gymnast will need careful control of the position of her CoM if she is not to fall off

36. indexpreviousnext AQA AS / A1 Level Physical Education 3.1.5.1 biomechanical principles 35 3.1.5 Biomechanical movement BALANCE and TOPPLING TOPPLING during a swim start, the swimmer topples forward during a swim start, the swimmer topples forward by adjusting the line of action of the weight acting through the CoM so that it falls in front of his / her feet by adjusting the line of action of the weight acting through the CoM so that it falls in front of his / her feet and then allows the toppling to tip him / her forwards into the water and then allows the toppling to tip him / her forwards into the water when the body is almost horizontal, he / she drives hard with the legs on the start platform when the body is almost horizontal, he / she drives hard with the legs on the start platform to propel him / her forward into the race to propel him / her forward into the race