Newton's Third Law: Action-Reaction Principle

Newton's first law is also known as the Law of Inertia.

Forces have 3 components: rotational, linear, and shear.

A body at rest will remain at rest unless acted upon by an external force according to Newton's first law.

A body in dynamic equilibrium has zero acceleration.

A body in static equilibrium has constant velocity.

Rotational movement requires an external torque to change its state according to Newton's first law.

Internal forces are generated by structures located outside the body.

Active forces are typically generated by tension in stretched periarticular connective tissues.

External forces are produced by forces acting from outside the body.

Sir Isaac Newton's observations about forces related to mass and motion were made in the 19th century.

Newton's 'Philosophiae Naturalis Principia Mathematica' provided the basic laws of mechanics for understanding human movement analysis.

Passive forces are generated by stimulated muscles under voluntary control.

Newton's third law states that for every action, there is an equal and opposite reaction.

The law of acceleration (F=ma) is not related to Newton's third law.

The ground reaction force (G) is the same as the foot force.

The effect each body experiences depends on its mass.

The law of action-reaction implies that the forces between two interacting bodies are always equal in magnitude.

Inertia is directly proportional to the amount of energy required to alter the velocity of a body.

Each body has a point known as the center of gravity (COG), where its mass is evenly distributed.

The center of mass (COM) of a body closely coincides with its center of gravity (COG) when subjected to gravity.

The mass moment of inertia depends only on the mass of the body.

The resistance to a change in angular velocity is indicated by the mass moment of inertia.

According to Newton's second law, the linear acceleration of a body is directly proportional to the force causing it.

The angular acceleration of a body is directly proportional to the torque causing it and inversely proportional to the mass-moment of inertia of the body.

If the sum of the forces acting on a body is zero, the body will accelerate in the direction of the resultant force.

The force-acceleration relationship is given by the equation F = m * a.

The torque-acceleration relationship is given by the equation M = I * a.