Unit 3 & 4 - Biomechanics Study Notes

UNIT 3 & 4 - Biomechanics 4th edition

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CONTENTS

  • Introduction to Biomechanics

  • Linear Kinetics
      - Newton’s 1st Law
      - Newton’s 2nd Law
      - Momentum
      - Force-time (Impulse)
      - Newton’s 3rd Law
      - Conservation of momentum
      - Coefficient of Restitution

  • Angular Kinetics
      - Angular momentum
      - Moment of inertia
      - Conservation of angular momentum
      - Levers
        - 1st class lever
        - 2nd class lever
        - 3rd class lever
      - Torque

  • Fluid mechanics
      - Turbulent flow
      - Laminar flow
      - Drag
        - Surface drag
        - Pressure drag
        - Wave drag
      - Bernoulli's principle
      - Magnus effect
      - Top spin
      - Back spin
      - Side spin
      - No spin

  • Application of biomechanical principles
      - Balance
      - Coordination
      - Force-motion
      - Force-time
      - Inertia
      - Optimal projection
      - Range of motion
      - Spin

  • References

INTRODUCTION TO BIOMECHANICS

  • What is Biomechanics?
      - The study of motion and the effects of forces relative to the body.
      - Applies laws of mechanics and physics to human performance.
      - Aids in improving mechanical aspects of sports performance.

Benefits of Biomechanics

  • Technique efficiency:
      - Enhances performance through better technique.

  • Injury reduction:
      - Understanding injury causes leads to applying correct technique.

  • Modification of sports equipment:
      - E.g., junior size equipment made lighter for ease of use.   - Technological advancements in cricket bats, golf equipment, tennis racquets, etc., improve power and accuracy.

  • Technological development:
      - Equipment and computer technology assist transition from practice to play (e.g., bowling machines in cricket, video software).

LINEAR KINETICS

  • Definition of momentum:
      - Momentum is defined as the product of mass and velocity.
      - Mathematical expression:
        Momentum=MassimesVelocityMomentum = Mass imes Velocity

  • Conservation of momentum:
      - Related to Newton’s Second Law of Motion.

  • Impulse–momentum relationship:
      - Understanding how impulse affects momentum.

  • Coefficient of restitution:
      - Measures elasticity of collisions.

Force

  • Definition:
      - Force is defined mathematically as:
        F=MAF = MA
      - Force is the interaction that changes the motion of an object.

  • Force applications:
      1. Get objects moving
      2. Stop objects moving
      3. Change direction of moving objects
      4. Change speed of moving objects
      5. Balance other forces to keep an object stationary

Types of Forces

  • Internal Forces:
      - Structure of the body (muscles and tendons) interacting to produce movement.

  • External Forces:
      - Result from interaction between body and environment, such as:   - Gravity, friction, air resistance, water resistance.

Types of External Forces

  1. Contact Forces:
      - E.g., frictional forces, ground reaction forces (GRF), air resistance, water resistance.

  2. Noncontact Forces:
      - E.g., gravity.

Newton’s Laws of Motion

  • Newton’s 1st Law (Law of Inertia):
      - A body remains in its state of rest or motion unless acted upon by a force. E.g.
        - A netball stays in a player's hands until force is applied.

  • Newton’s 2nd Law (Law of Acceleration):
      - Acceleration is directly proportional to the force and inversely proportional to mass.
        - Expressed as:
          F=maF = ma
      - More force = more acceleration; same force, less mass = more acceleration.

  • Newton’s 3rd Law (Action-Reaction):
      - For every action, there is an equal and opposite reaction.

Momentum

  • Definition:
      - The measure of motion possessed by a moving body, calculated as
        Momentum=MassimesVelocityMomentum = Mass imes Velocity.

  • Implications:
      - Greater momentum needs more force to stop or slow down an object.

Impulse-Momentum Relationship

  • Definition:
      - Application of force over time to change momentum of an object.

  • Formula for impulse:
      - Impulse=ForceimesTimeImpulse = Force imes Time
      - Creates momentums: increases, decreases, or takes it back to zero.

Practical Example in Sports

  • Catching a ball:
      - Preferably use smaller peak force over longer period to reduce peak impact and increase catching effectiveness.

ANGULAR KINETICS

  • Angular Momentum:
      - Resistance of a rotating body to change state of motion, related to its angular position.

  • Moment of Inertia:
      - Resistance to change in an object’s rotational motion, defined as
        MomentextofInertia=MassimesRadiusextofRotationMoment ext{ of Inertia} = Mass imes Radius ext{ of Rotation}.

Levers

  • Definition:
      - Levers have three components: Resistance, Axis, and Force.

  • Classes of Levers:
      - 1st Class: Axis between Force and Resistance (e.g., neck).   - 2nd Class: Resistance between Axis and Force (e.g., calf raise).   - 3rd Class: Force between Axis and Resistance (e.g., bicep curl).

Torque

  • Definition:
      - Torque is the turning effect caused by a force applied around a pivot or axis.
      - Formula:
        Torque=ForceimesDistanceTorque = Force imes Distance

  • Maximizing Torque:
      - Apply greater force; increase distance of force application from axis.   

FLUID MECHANICS

  • Fluid Mechanics Definitions:
      - Fluid: any liquid or gas.   - Laminar flow: smooth, orderly flow.   - Turbulent flow: chaotic or erratic flow.

  • Drag Types:
      - Surface Drag: friction between fluid and surface.   - Pressure Drag: differential pressure across an object.   - Wave Drag: resistance from wave generation in water.

Bernoulli’s Principle

  • Definition:
      - Principle that relates the speed of fluid and pressure; as velocity increases, pressure decreases.

Magnus Effect

  • Definition:
      - Effect of spin on an object's trajectory in a fluid; applies Bernoulli's principle to explain the curve in an object's path.

APPLICATION OF BIOMECHANICAL PRINCIPLES

  • Balance:
      - Ability to maintain equilibrium; affected by mass, base of support, height of center of gravity, and position of line of gravity.

  • Coordination:
      - Interaction between body segments for effective movement.

  • Force-Motion and Force-Time:
      - How forces create motion and time over which these forces are applied.

  • Inertia:
      - Resistance to change in motion; reduced moment of inertia aids greater velocity.

  • Optimal Projection:
      - Optimal angle for maximizing distance/travel; typically between 40-43 degrees.

  • Range of Motion:
      - The extent of joint motion; larger range allows more velocity.

  • Spin:
      - Affects the flight path and interaction with surfaces; different types include topspin, backspin, and sidespin.

REFERENCES

  • A collection of various educational texts and resources in the field of physical education and biomechanics suitable for further reading and understanding.