Week 2 Linear Kinematics

Recap of Topics Covered

• Definition of Sports Biomechanics

• Various topics included in the course

• Importance of biomechanics in sport

What is Biomechanics?

• Study and analysis of human movement patterns in sport (Bartlett et al. 2007)

• Bio: Biological systems

• Mechanics: Study of motion in time and space

• Application of mechanics (maths & physics) to biological systems

• Historically termed kinesiology:

  • Kine: Greek for 'movement'

  • Ology: Study of

• Field is too broad; encompasses functional anatomy and human movement science

Areas of Study in Biomechanics

Functional Anatomy

• Understanding the body's structure and its functions.

Kinematics

• Describes motion without considering forces.

Kinetics

• Involves the analysis of forces and torques acting on a body.

Mechanics

• Examination of movement with respect to linear and angular positions, velocities, and accelerations.

Linear Kinematics

• Focuses on the motion of the human body.

• Not concerned with causes of movement but rather describing:

  • How far, how fast, and consistency of motion.

• Valuable for athletic performance analysis, identifying strengths/weaknesses, and determining the effectiveness of interventions.

Forms of Motion

• Linear (Translational) Motion: All body parts travel the same distance and in same direction.

• Angular (Rotational) Motion: A body or segment rotates about an axis.

• General Motion: Combination of linear motion of the center of mass and rotation of body segments.

• Types of linear motion:

  • Rectilinear: Straight line movement

  • Curvilinear: Movement in a curve, but body remains fixed.

Kinematic Analysis in Biomechanics

Key Terms

• Position: Location in space versus a baseline. Recorded as x, y coordinates (or x, y, z for 3D).

• Reference Systems: A coordinate system must be established for kinematic analysis.

• Position Vector: Defined by components in x and y directions.

• Vector Representation: Vectors depict position, distances, and orientation. Length and direction represented graphically by arrows.

Distance and Displacement

• Distance: Total path covered during motion (scalar)

• Displacement: The straight-line distance between initial and final positions (vector).

Task on Distance and Displacement

Example: Swimming 3 lengths in a 50m pool.

• Distance: Total distance swum.

• Displacement: Straight-line path from start to finish.

Scalar and Vector Quantities

• Scalar Quantities: Defined by magnitude only (e.g., distance, speed, time).

• Vector Quantities: Defined by magnitude and direction (e.g., displacement, velocity, acceleration).

• Examples in Sports Context:

  • Total distance (scalar) vs. displacement from start to end (vector).

Vector Addition

• Vectors can be summed using methods such as:

  • Nose to Tail

  • Parallelogram Method

Speed and Velocity

Definitions

• Speed (Scalar): Total path length divided by time.

• Velocity (Vector): Change in position divided by time.

• Example: Calculate Usain Bolt’s average velocity in 100m sprint.

Acceleration

• Defined as the rate of change of velocity with time.

• Can be positive (increase in speed), negative (deceleration), or zero (constant speed).

Summary of Concepts

• Distance and speed: scalar quantities; displacement and velocity: vector quantities.

• Resultant vector and angle can be calculated using Pythagorean theorem and trigonometry.

• Average acceleration: change in velocity divided by time.

• Kinematics provide a framework for analyzing movements classified by type (linear, angular, general) and measured by specific parameters.