Definition: Describes motion without considering forces causing the motion.
Focus: Position, velocity, and acceleration of objects.
Linear Motion: Analyzes particles or objects moving in straight or curved lines, not around an axis (which would be angular motion).
Key Concepts and Definitions
Position
Position: Location of a particle at a specific point in time.
Distance and Displacement
Distance: Scalar quantity, total path length traveled.
Displacement: Change in position, final minus initial position, vector quantity.
Speed and Velocity
Speed: Scalar, distance over time.
Velocity: Vector, displacement over time, includes direction.
Acceleration
Acceleration: Rate of change of velocity over time, vector quantity.
Coordinate System
Cartesian Coordinates: X, Y, and Z (three-dimensional space).
Example: Tracking motion in two dimensions (X and Y), but can consider Z for three-dimensional analysis.
Analyzing Motion
Digitizing Movement: Tracking motion using coordinates (e.g., a toe kicking a ball).
Modeling Motion: Choice of tracking point (e.g., center of an object) affects analysis.
Displacement and Distance
Displacement in Motion: Focus on change in position, A to B.
Distance in Motion: Total path length, can be longer due to snaking or curved paths.
Biomechanics and Gait Analysis
Gait Cycle: Analyzing the position of the center of gravity during running.
Vertical and Horizontal Movement: Bouncing up and down in walking/running cycles.
Velocity Analysis
Average vs. Instantaneous Velocity
Average: Overall speed across a distance (e.g., 50m race).
Instantaneous: Speed at a specific point (e.g., at 30m mark).
Velocity Units: Meters per second (m/s).
Graphical Analysis
Displacement and Velocity Graphs: Use of slope in graphs to determine velocity and direction.
Acceleration
Definition: Change in velocity, vector quantity (m/sĀ²).
Average vs. Instantaneous Acceleration
Average: Over entire event (e.g., race).
Instantaneous: At a specific moment (e.g., start of race).
Acceleration in Motion: Changes in velocity direction/magnitude.
Practical Examples
Sports Analysis: Using examples from sprinting or baseball to understand velocity and acceleration.
Gait Analysis and Timing
Phases of Gait
Stance Phase: 60% of walking cycle, foot on ground.
Swing Phase: 40% of walking cycle, foot in the air.
Stride Length and Frequency: Determinants of walking/running speed.
Conclusion
Key Focus for Study: Understanding and differentiating between displacement, velocity, and acceleration as these are critical for biomechanics and kinematics analysis.