Download Biomechanical Concepts

Biomechanical Concepts
Acceleration:
The rate at which the velocity of a body changes with time.
Center of Gravity:
The center of gravity is a geometric property of any object. The center of gravity is the average location of the
weight of an object. We can completely describe the motion of any object through space in terms of the
translation of the center of gravity of the object from one place to another and the rotation of the object
about its center of gravity if it is free to rotate. If the object is confined to rotate about some other point, like a
hinge, we can still describe its motion. In flight, both airplanes and rockets rotate about their centers of
gravity. A kite, on the other hand, rotates about the bridle point. But the trim of a kite still depends on the
location of the center of gravity relative to the bridle point, because for every object the weight always acts
through the center of gravity.
Centripetal Force:
 A force that makes a body follows a curved path.
 Centripetal force is generally the cause of circular motion.
Deformation:
Deformation is a change in the shape or size of an object due to an applied force (the deformation energy in
this case is transferred through work) or a change in temperature (the deformation energy in this case is
transferred through heat).
Equilibrium:
The condition of a system in which all competing influences are balanced, in a wide variety of contexts.
Friction:
Four types of friction:
1. Sliding friction: ice skating
2. Rolling friction: bowling
3. Fluid friction (air or liquid): air or water resistance
4. Static friction: initial friction when moving an object
Force:
A force is any influence that causes an object to undergo a certain change, either concerning its movement,
direction, or geometrical construction. In other words, a force can cause an object with mass to change its
velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or a flexible object to deform,
or both. Force can also be described by intuitive concepts such as a push or a pull. A force has both magnitude
and direction, making it a vector quantity. It is measured in the SI unit of newton’s and represented by the
symbol F.
The original form of Newton's second law states that the net force acting upon an object is equal to the rate at
which its momentum changes with time. If the mass of the object is constant, this law implies that the
acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the
net force, and is inversely proportional to the mass of the object. As a formula, this is expressed as:
\vec{F} = m \vec{a} where the arrows imply a vector quantity possessing both magnitude and direction.
Inertia:
The resistance of an object to change its state of being (motion or stillness).
Projectile:
A projectile is any object projected into space (empty or not) by the exertion of a force. Although any object in
motion through space (for example a thrown baseball) may be referred to as a projectile. Mathematical
equations of motion are used to analyze projectile trajectory.
Net Force:
Net force is the overall force acting on an object.
Radius:
The radius of a circle or sphere is the length of a line segment from its center to its perimeter.
Range of Motion:
Range of motion (or ROM), is the distance (linear or angular) that a movable object may normally travel while
properly attached to another. It is also called range of travel, particularly when talking about mechanical
devices and in mechanical engineering fields. For example, a volume knob (a rotary fader) may have a 300°
range of travel from the "off" or muted (fully attenuated) position at lower left, going clockwise to its
maximum-loudness position at lower right.
As used in the biomedical and weightlifting communities, range of motion refers to the distance and direction
a joint can move between the flexed position and the extended position. The act of attempting to increase this
distance through therapeutic exercises (range of motion therapy—stretching from flexion to extension for
physiological gain) is also sometimes called range of motion.
Resistance:
Fluid or gas forces opposing motion and flow
Speed:
The speed of an object is the magnitude of its velocity (the rate of change of its position); it is thus a scalar
quantity. The average speed of an object in an interval of time is the distance travelled by the object divided
by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of
the time interval approaches zero.
Torque:
The tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a
torque can be thought of as a twist to an object. Mathematically, torque is defined as the cross product of the
lever-arm distance and force, which tends to produce rotation.