Angular Kinematics: Angular Motion Lecture Notes

Angular Kinematics

Angular motion: All parts of a body move through the same angle

1. General Motion

• General motion can be categorized into two types:

  • Rotation: Movement around an axis (e.g., spinning).

  • Translation: Movement in a linear path.

2. Centre of Rotation

• The point about which angular motion occurs; this is fundamental in understanding how limbs and body segments move.

3. Measuring Angles

• Angles are essential in the analysis of motion. Various units are employed for measurement:

  • Degrees (°): A standard unit for measuring angles, with a full circle comprising 360 degrees.

  • Radians (rad): Defined such that 1 radian is the angle subtended at the center of a circle by an arc whose length is equal to the circle's radius.

  • Formula for Circumference: C = 2\pi r

  • Therefore, a full circle (360°) can be expressed in radians as 2\pi radians.

  • Revolutions: One complete turn around a point refers to an angle of 360° or 2\pi radians.

4. Absolute Angles

• Definition: Absolute angles refer to the measurement from an external reference frame.

• Commonly measured in the anticlockwise direction from the right horizontal (0° reference).

5. Relative Angles

• Definition: Relative angles denote the angle formed between two limb segments.

• These angles can be defined as:

  • Degrees of flexion at a joint, impacting motion and biomechanics.

  • The specific angle formed at an articulation (joint).