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.