1. Biomechanics The study of cause and effect
FORM 6 PED

3. Why study Biomechanics?
To understand how people can move.
1. To enhance skill performance
elite athletes
physical challenges

4. Why study Biomechanics?
2. To lower the risk for injury
Exercise equipment & technique
shoes & surfaces
braces & orthotics
Automobiles
collisions

5. Why study Biomechanics?
Can a cow really jump over the moon?

6. Define a Force

7. Forces and Levers A force is a push or pull.
When a force acts upon a body (object) it can produce 3 types of movement.
Translation – Moves from A to B.
e.g. A golf shot starts on the tee and finishes on the fairway.

8. Rotation – If force not applied through the centre of gravity the object will rotate e.g. putting spin on a volleyball serve.

9. Deformation – The object loses shape on impact e. g
Deformation – The object loses shape on impact e.g. a squash ball being hit

10. The main force acting on all parts of the body is gravity.
Centre of gravity (COG) can therefore be defined as the point at which all parts of the body are in balance.
In men, the COG is about 57% of standing height, in women 55%. Women have more mass concentrated around the hips and below and this gives them an advantage in balance related activities.

12. These are known as the AXIS OF ROTATION
When we produce rotation as a consequence of a force being applied, the body rotates about the COG.
These are known as the AXIS OF ROTATION

13. The body rotates around three different axes.
Longitudinal
E.g. Pirouette in dance, twist in diving, spinning in ice skating

14. 2. Transverse
e.g. forward / backward roll/ somersault

15. 3. Sagital
e.g. cartwheel, cricket delivery,

16. Levers
A lever is basically a rigid structure, hinged at some part and to which forces are applied at two other points.
Levers consists of three parts.
Resistance
Effort
Falcrum or pivot
The point of support, or axis, about which a lever may be made to rotate

17. FUNCTIONS OF A LEVER Levers perform two main functions:
To increase the resistance that can be moved with a given effort, eg. Crowbar.
To increase the velocity at which an object will move with a given force, eg. Golf club
There are three classes of lever.

18. Levers-First Class
In a first class lever the fulcrum is in the middle and the load and effort is on either side
Think of a see-saw

19. Levers-Second Class
In a second class lever the fulcrum is at the end, with the load in the middle
Think of a wheelbarrow

20. Levers-Third Class
In a third class lever the fulcrum is again at the end, but the effort is in the middle
Think of a pair of tweezers

25. Newton’s Laws of Motion
Sir Isaac Newton ( ) developed 3 laws to explain relationship between the forces acting on a body and the motion of a body.

26. Law 1
“An object at rest tends to remain at rest unless acted upon by some external force”
This is known as Inertia. High level of inertia can be advantageous and disadvantageous in different sports.

27. Law 2
“When a force acts upon a mass, the result is acceleration of that mass”
The greater the force, the greater the acceleration
The smaller the mass, the greater the acceleration
The mass will accelerate in the direction the force is applied
Force = mass x acceleration
(F=MA)

28. Law 3 “For every action, there is an equal and opposite reaction”
These 2 forces always work in pairs
action force
reaction force

29. The big question.. Analysing the Overhead Serve in Volleyball
Try analysing the volleyball serve.
Ask yourself “ How is the biomechanical principle – Newton’s Laws of Motion being applied to the overhead serve in volleyball? Where can I see this being applied?
This will help you to explain how they contribute to the performance of the serve.

30. Principles of Balance and Stability
What is Stability?

31. Stability
Stability is defined as the ability to hold or maintain a position in space.

32. Stability The two main elements in maintaining stability are:
The position of the COG with respect to the base of support.
The direction of the forces involved.

33. Principle 1
The closer the line of gravity is to the centre of the base of support, the greater the probability of maintaining balance.

34. Principle 2
The broader the base of support, the greater the probability of maintaining balance.

35. Principle 3
The probability of maintaining balance is increased when the COG is lowered in relation to the base of support.

36. Principle 4
The further the body part moves away from the line of gravity, the probability of maintaining balance decreases unless another body part moves to compensate for it.

37. Types of Motion
There are 4 main types of motion;

38. A) Linear Motion
When parts of the body move in straight parallel lines. Quite rare in sporting situations.
e.g. tobogganing down a hill, dropping a ball, sliding into first base

39. B) Curvilinear Motion
When points in the body move in curved parallel lines.
e.g. free fall skydiving, path of an arrow
If the path of two points on a body follow straight parallel
lines, the motion is linear. If the path is curved, the motion
is curvilinear.

40. C) Angular Motion
Rotation about an axis that can be internal (axis inside the body) or external (axis outside the body). E.g. swinging on a high bar, a forward roll, hammer throwing, pole vault over bar, softball pitch, fosbury flop.

41. D) General Motion
Linear motion of the body as a result of angular motion of other parts of the body.
e.g. cycling, swimming, using a wheelchair

42. Torque ? Torque is a turning force. Eccentric force produces spin.
It depends on how far the mass is from the axis and the size of the mass.
How do we produce topspin or backspin ?
Where do we hit the ball ?
How can we generate more spin ?

43. Momentum
Momentum is moving inertia. We can rewrite Newton’s 1st law to include momentum.
“An object that is moving will continue to move in the direction the force was applied until another force is applied”
The greater the momentum the greater the force required to stop it e.g. small /large snowball.
Momentum (kgms) = mass (kg) x velocity (ms)

44. Momentum can act when an object is translating. This is linear momentum.
Momentum can act on an object when it is rotating. This is angular momentum.

45. Conservation of Momentum
When objects collide, momentum is conserved throughout.
Momentum before impact = momentum after impact.
MOMENTUM = MASS X VELOCITY
kgms kg ms

46. Use the information on Conservation of Momentum and steps below to calculate the speed of the golf ball after impact.
A golfer swings a 0.35kg club at 30m/s to hit a 0.004kg golf ball off the tee. After impact his club speed drops to 25m/s.
Remember
Momentum before impact = Momentum after impact. (M = m x v)
Club Momentum
Ball Momentum
Total Momentum
Before Impact
After Impact

47. What is the Ball Velocity?
Momentum = mass x velocity
Velocity = momentum
mass

48. Use the information on Conservation of Momentum and steps below to calculate the speed of the hockey stick after impact.
A ice hockey player uses their stick to strike a 500 gram (0.5kg) puck moving at 2m/s toward their opponent’s goal. The stick has a mass of 2kg and possesses stick head velocity of 25m/s before impact. After impact, the stick head velocity decreases to 17m/s.
Remember
Momentum before impact = Momentum after impact. (M = m x v)
Stick Momentum
Puck Momentum
Total Momentum
Before Impact
After Impact