Chapter 4 Flashcards
Law of Inertia - Linear Movement
An object at rest stays at rest and an object in motion statys in motion with the same speed and in the same direction (velocity) unless acted on by an external force.
Law of Inertia- Angular Movement
An object will maintain a constant angular velocity unless acted on by an external torque (moment).
Law of Acceleration - Linear Movement
The linear acceleration of an object is produced by a force directly proportional to that force and inversely proportional to the object’s mass. F=m*a
Law of Acceleration- Angular Movement
The angular acceleration of an object is produced by a torque (moment) directly proportional to that torque and inversely proportional to the object’s moment of inertia. M= I *~
Law of Reaction- Linear Movement
For every force, there is a reaction force equal in magnitude and opposite in direction.
Law of Reaction- Angular Movement
For every torque (moment), there is reaction torque (moment) equal in magnitude and opposite in direction.
How is mechanical work defined?
Work (W) is the product of a force (F) causing a change in position and the magnitude of this linear displacement (d).
(W)= F*d example- if a clients moves a squat bar exactly 2 ft. with 200lb of force, the total work done is 400 ft-lb.
Power is
linearly defined as the product of force and velocity an is a method to quantify the work rate of a client.
P= F x (D/t) = F x V = W/t
Angular Power is
The ability to create a large peak of angular power i.e.- tennis serve requires clients to impart force on a ball with a relatively large lever arm at a high angular velocity.
Angular power = M (angular movement) * work (angular velocity)
Active force is
produced from a sliding-filament theory and may be thought of the amount of force an individual intends to produce and is directly related to the magnitude of the command signal that exits the spinal cord and propagates the muscle.
Passive force
comes from the tendency of a muscle to resist being lengthened. If an external load is placed on a muscle that causes it to lengthen, the material propeties of the muscle and musculotendinous junction will exert a force opposing that lengthening.
Eccentric muscle contraction
lengthening- Eccentric contractions occur when a muscle opposes a stronger force and reverse its initial trajectory. Eccentric contractions are sometimes referred to as braking contractions, negative work, or simply “negatives.” 2 Eccentric contractions are essentially the yin to concentric contractions’ yang
Concentric muscle contraction
a concentric contraction is one in which the tension on a muscle increase as it shortens. 1 Concentric contractions are a central aspect of the growth and development of muscles. As muscle contracts, they begin the process of hypertrophy (“hyper” meaning increased and “trophy” meaning growth).
The total force produced during a movement is a combination of
active and passive muscle forces.
The velocity of muscular contraction also affects
the force output.
