Q.Define principle of force–time.

The nine biomechanics principles are the minimum set of core principles that apply to all human movement, based on the work of biomechanists such as Norman (1975) and Hudson (1995). They split into principles governing the CREATION of movement (the process) and principles governing the OUTCOME of projectiles (the product).

The process principles are: (1) Force-Motion -- unbalanced forces (and the torques they induce) are needed to create or modify motion; a person standing still has balanced forces and so does not move. (2) Force-Time -- how long a force is applied matters as much as how large it is (Impulse = Force x Time), which is why a hockey sweep shot (more force AND more time) carries more power than a quick hit, and why increasing contact time helps in catching or landing safely. (3) Inertia -- the property of an object to resist a change in its state of motion, measured by mass (linear inertia) or moment of inertia (angular inertia); a heavier shotput has more inertia to overcome than a netball. (4) Range of Motion -- the overall linear or angular motion used in a movement; a reduced range of motion suits low-effort, high-accuracy skills (a dart throw), while an increased range of motion suits maximum force/speed skills (a javelin throw). (5) Balance -- a person's ability to control body position relative to a support base; stability increases with a wider base of support, a lower centre of gravity, and more mass, with the line of gravity falling in the middle of the base (a sumo wrestler's wide, low stance). (6) Coordination Continuum -- whether muscle actions and joint rotations happen simultaneously (favoured for high-force goals, e.g. weightlifting) or sequentially (favoured for high-speed, lower-force goals, e.g. a baseball pitch). (7) Segmental Interaction -- forces …