- Dynamic: an object wants to stay in motion unless acted upon by another force.
Dynamic inertia can be motive or resistive.
- Motive: assists when moving an object (momentum).
- Resistive: forces working against motion.
Constraint: limiting factor and there are two main types:
Environmental constraints
- Spacial
- Temporal
Biomechanical constraints
- Leverage
- Friction
- Gravity
- Morphology
- Time lags (time is takes for a signal to travel from the sensory nerve to the brain and
back to the motor nerve). - Zooms
- Newton’s Second Law of Motion
The relationship between an object’s mass (m), its acceleration (a), and the applied force
(F) is simplified in the formula F= ma. This law states that the direction of the force vector
is in the same direction of the mass’s acceleration vector.
F = ma
- Newton’s Third Law of Motion
For every action there is an equal and opposite reaction.- Center of Gravity
This is depicted as the balance point, or the specific area on which the surrounding forces
are equal to zero. It is seen as the concentration of mass. Although, the center of gravity
changes through all motions seen in the human body, it is typically around the umbilicus,
and moves toward the displaced limb. The closer the center of gravity is to your base
of support, the more stability. Posture attempts to balance the forces in the body so their
sum equals zero.
Law of falling bodies:
The rate that gravity pulls one to the ground. Objects accelerate to the ground regardless
of weight, as long as air is not a factor. The rate of acceleration due to gravity is Z32 ft/sec^2 or
9.8 m/sec^2.