Kin6

• Force System

  Two important points to be aware of: the point of application of the force (where the force is applied) and the line of action of the force (direction)
• Force

  A push or pull on an object
• Vector

  Represented by an arrow, length is proportional to magnitude
• Combination of Vectors

  Vectors may be combined by addition, subtraction, or multiplication to get a new vector called the resultant (R)
• Resultant (R)

  The new vector created by combining other vectors, its direction is towards the bigger force

  
• Types of Force Systems

  • Linear (Collinear)

  2. Parallel (Coplanar)

  3. Concurrent

  
• Linear (Collinear) Force System

  Forces acting along the same action line, may produce tension or compression effect
• Linear Force System (Collinear)

  • A. Forces in the same direction (e.g. Psoas major and iliacus muscles)

  B. Forces in opposite directions (e.g. Trapezius muscle on both sides)
• Parallel (Coplanar) Force System

  Forces acting in the same plane, at two different points, and parallel to each other, but do not share the same action line. Forces produce rotatory effects.

  
• Parallel Force System

  • A. Parallel forces in the same direction (e.g. Hamstring muscles)

  B. Couple force (e.g. Turning steering wheel with two hands)

  
• Concurrent Force System

  Forces meet at the same point of application, do not lie along the same line of action, but form an angle with each other

  
• Concurrent Force System

  • Medial and lateral gastrocnemius

  Anterior, middle, posterior deltoid