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Physics of Motion and Forces in Sports

Newton’s Laws of Motion

  • Linear and Angular Motion

    • Newton's laws can analyze both linear and angular motion.

  • Collision and Momentum

    • A collision results in a change in momentum in colliding bodies.

  • Friction

    • The force of friction is determined by the coefficient of friction.

  • Work

    • Work results from the application of a force over a distance.

Introduction to Kinematics

  • Kinematics Definition

    • Study of motion, defined as the change in position of a body or object.

  • Types of Motion:

    • Linear Motion: Moving in a straight line (e.g., ice hockey puck).
    • Curvilinear Motion: Moving in a curve (e.g., a shot-put).
    • Angular Motion: Rotational movement around an axis (e.g., gymnast on a high bar).
    • General Motion: Combination of linear and angular motion.

  • Application in Sports: Most common human motion is general due to limb rotations.

Fundamentals of Biomechanics

  • Key Concepts: Speed, velocity, distance, displacement, and acceleration.

Speed in Sports

  • Comparison of Speeds: Examples include Usain Bolt's 200m record and Vendée Globe sailing speeds.

  • Average Speed Calculation:

    • Average speed = Total distance / Total time
    • Speed is a scalar quantity (e.g., 15 km/h).

Velocity vs. Speed

  • Velocity:

    • A vector quantity described by magnitude and direction (e.g., 15 km/h east).
    • Average velocity = Displacement / Time.

  • Scalar vs. Vector:

    • Scalars have only magnitude.
    • Vectors have both magnitude and direction.

Linear Kinematics

  • Distance vs. Displacement:

    • Distance is total path length traveled (scalar).
    • Displacement is straight-line distance from start to endpoint (vector).

  • Calculating Speed and Velocity:

    • Speed = Distance / Time
    • Velocity = Displacement / Time.

Linear Acceleration

  • Acceleration Definition:
    • The rate of change of velocity (vector quantity).
    • For example, a skater increasing speed from 2.0 m/s to 10.0 m/s in 3.0 seconds.

Angular Kinematics

  • Angular Motion:

    • Important in sports involving rotation (e.g., figure skating).
    • Coaches can use angular kinematics to improve performance and reduce injury risk.

  • Angular Displacement and Velocity:

    • Angular displacement: difference between starting and ending positions (in degrees or radians).
    • Angular velocity: rate of change of angular position (vector quantity).

Newton’s Laws of Motion

  • First Law (Inertia):

    • An object remains at rest or constant velocity unless acted upon by an unbalanced force.

  • Second Law:

    • Force = Mass x Acceleration (F=ma).
    • Acceleration is proportional to net force and inversely proportional to mass.

  • Third Law:

    • For every action, there is an equal and opposite reaction.

Applications of Newton’s Laws in Sports

  • Examples:
    • First Law: A ball struck remains in motion unless acted on by external forces.
    • Second Law: More force leads to more acceleration for a given mass.
    • Third Law: An athlete pushing off starting blocks demonstrates action-reaction force.

Momentum

  • Definition:

    • Momentum is the product of mass and velocity (p = mv).
    • It is a vector quantity.

  • Impulse-Momentum Theorem:

    • Impulse is the product of force and time, leading to a change in momentum.

  • Conservation of Momentum:

    • In a closed system, total momentum remains constant (e.g., during collisions).

Centre of Mass

  • Definition:

    • The balance point of a body where mass is evenly distributed.

  • Importance in Sports:

    • Shifting the centre of mass can enhance performance (e.g., high jump techniques).
    • External forces affect the centre of mass during athletic movements.