1. Kinetics and Kinematics
   1. Kinetics and Kinematics
      1. Kinematics
         1. describes the motion of the bodies and deals with finding out velocities or accelerations for various objects.
      2. Kinetics
         1. deals with the forces or torque applied on a body
   2. Kinematic Concepts for Analyzing Human Motion
      1. Anatomical Reference Planes
         1. A plane
            1. is a two-dimensional surface with
            2. an orientation defined by the spatial
            3. coordinates of three discrete points not all
            4. contained in the same line
         2. Sagittal plane
            1. divides the body vertically
            2. into left and right halves
         3. Coronal plane
            1. splits the body vertically
            2. into front and back halves of equal mass
         4. Transverse plane
            1. separates the body into
            2. top and bottom halves of equal mass
   3. Kinematic Concepts for Analyzing Human Motion
      1. Forms of Motion
         1. . Linear Motion
            1. Pure linear motion involves uniform motion of the system of interest, with all system parts moving in the same direction at the same speed.
            2. If the line is straight, the motion is rectilinear; if the line is curved, the motion is curvilinear.
         2. Angular Motion
            1. is rotation around a central imaginary line known as the axis of rotation
         3. General Motion
            1. When translation and rotation are combined, the resulting movement is general motion.
2. Basic Concepts Related to Kinetics
   1. 1. Inertia
      1. resistance to action or change
      2. the mechanical definition is resistance to acceleration.
      3. is the tendency of a body to maintain its current state of motion
         1. motionless
         2. moving with a constant velocity.
      4. no units of measurement
      5. the amount of inertia a body possesses is directly proportional to its mass.
      6. The more massive an object is
         1. the more it tends to maintain its current state of motion
   2. 2. Mass
      1. is the quantity of matter composing a body.
      2. unit
         1. kilogram (kg)
   3. 3. Force
      1. A force (F) can be thought of as a push or a pull acting on a body.
      2. Each force is characterized by
         1. its magnitude, direction, and point of application to a given body.
      3. example
         1. Body weight
         2. friction
         3. air
         4. water resistance
      4. The action of a force causes a body's mass to accelerate
         1. F = ma
      5. Units
         1. units of mass multiplied by units of acceleration
         2. Newton (N)
            1. which is the amount of force required to accelerate 1 kg of mass at 1 m/s²
            2. 1 N = (1 kg)(1 m/s²)
      6. all forces that commonly act on the human body.
   4. 4. Center of Gravity
      1. A body’s center of gravity, or center of mass,
         1. is the point around which the body’s weight is equally balanced, no matter how the body is positioned.
      2. In motion analyses,
         1. the motion of the center of gravity serves
            1. as an index of total body motion.
      3. From a kinetic perspective, the location of
         1. the center of mass determines the way in
            1. which the body responds to external forces
   5. 5. Weight
      1. the amount of gravitational force exerted on a body.
      2. (ag): wt= mag
      3. units
         1. N or lb.
      4. As the mass of a body increases
         1. its weight increases proportionally.
      5. The factor of proportionality is
         1. the acceleration of gravity
            1. -9.81 m/s².
   6. 6. Pressure
      1. force (F) distributed over a given area (A)
         1. F= A *P
      2. Units
         1. (N/cm²) and Pascals (Pa).
         2. (Pa = N/m²). (psi or lb/in²).
   7. 7. Density
      1. The concept of density combines the mass of a body with the body volume.
      2. Density is defined as mass per unit of volume. The conventional symbol for density is the Greek letter rho (p).
         1. density (p) = mass/volume
      3. Units
         1. (kg/m³)
         2. In the English system
            1. not commonly used. Instead, units of specific weight (weight density) are employed.
   8. 8. Torque
      1. moment of force.
         1. which may be thought of as a rotary force, is the angular equivalent of linear force.
      2. Algebraically
         1. torque is the product of force (F) and the perpendicular distance (d) from the force's line of action to the axis of rotation:
            1. T=Fd
      3. The greater the amount of torque acting at the axis of rotation
         1. the greater the tendency for rotation to occur.
      4. Units
         1. Newton-meters (N-m) or foot-pounds (ft-lb).
   9. 9. Impulse
      1. When a force is applied to a body
         1. the resulting motion of the body is dependent not only on the magnitude of the applied force
         2. also on the duration of force applicatia.
      2. The product of force (F) and time (t)
         1. (J): = Ft
3. Mechanical Loads on the Human Body
   1. Compression
      1. pressing or squeezing force directed axially through a body
   2. Tension
      1. pulling or stretching force directed axially through a body
   3. Shear
      1. force directed parallel to a surface
   4. Mechanical Stress
      1. force within a body, quantified as force divided by the area over which the force acts
      2. The amount of mechanical stress created by a force is inversely related to the size of the area over which the force is spread.
   5. Torsion
      1. load-producing twisting of a body around its longitudinal axis
   6. Bending
      1. asymmetric loading that produces tension on one side of a body's longitudinal axis and compression on the other side
   7. Combined Loads
      1. simultaneous action of more than one of the pure forms of loading
   8. The Effects of Loading
      1. When a force acts on an object, there are two potential effects.
         1. acceleration
         2. deformation (change in shape).
      2. The relationship between the amount of force applied to a structure and the structure’s response is illustrated by a load-deformation curve
      3. yield point (elastic limit)
         1. point on the load deformation curve past which deformation is permanent
      4. acute loading
         1. application of a single force of sufficient magnitude to cause injury to a biological tissue
      5. failure
         1. loss of mechanical continuity
      6. repetitive loading
         1. repeated application of a subacute load that is usually of relatively low magnitude
4. Vector Algebra
   1. A vector
      1. A vector is a quantity that has both magnitude and direction,
      2. represented by arrow-shaped symbols.
      3. The magnitude of a vector is represented by its length and orientation indicates its direction.
      4. Example: Force, weight, pressure, specific weight, and torque are kinetic vector quantities; displacement, velocity, and acceleration
   2. Scalar
      1. quantities possess magnitude but have no particular direction
         1. associated with them.
      2. Example: Mass, volume, length, and speed
   3. Vector Composition
      1. To sum the effects of two or more forces acting on a given
         1. object we can use an
            1. operation is called vector composition
   4. Vector Resolution
      1. When a vector is resolved into perpendicular components
      2. a process known as vector resolution