Angular Kinematics

Angular Motion

All points on a body move in circles about a fixed axis. Examples: whole-body rotation (ice skater), segment rotation (flexion/extension), external axis (child on swing).

Measuring Angles

Goniometer measures joint angles. Joint movement is measured away from anatomical position. Fully extended joint = 0°.

Angular Distance (Scalar)

Length of angular path traveled.

Angular Displacement (Vector)

Change in angular position from start to finish. Defined by magnitude + direction. Units: degrees, radians, revolutions.

Angular Displacement Example

At the end of a bicep curl, when the forearm returns to start, angular displacement = 0.

Angular Velocity

Rate of change in angular position. Formula: angular displacement ÷ time. Units: degrees/sec or revolutions/min.

Angular Acceleration

Rate of change in angular velocity. Formula: change in angular velocity ÷ time. Units: degrees/sec². Can be positive or negative.

Inertia and Angular Motion

Greater inertia → smaller angular acceleration. Smaller inertia → greater angular acceleration.