Center of Mass
CoM & CoG
Center of GravityA point at or near the object through
which the resultant weight of the object passes
Center of Mass point at which the object's mass can
be assumed, for many purposes, to be concentrated
COM
• The point around which a body’s weight is equally balanced in all directions• Also referred to as the center of mass or mass centroid• Need not be physically located inside of a body
Center of Mass
• Specific point at which a system of particles behaves • a concentrated system• a function of only the positions and masses of particles comprising a system.
a) Neutralb) Stablec) Unstable
Center of Gravity
Serves as an index of total body motionBy locating CM can analyze motion of the
entire system as distinguished from the motion of its individual parts
Path of the center of gravity of a runner.
Methods to assess CG
1. Reaction Board technique which is easily applied to static positions
2. Balance Board technique which has limited application and is used for static positions
3. Segmentation method involves an estimation of individual segment masses and positions
Balance Board Technique
Reaction Board Technique
Segmental Method
Position of the end points of all of the body’s segments
Mass of each segmentLocation of CoM within each segment
Segmental Method
14 body segments:TrunkHead and neckRight and left thighsRight and left lower legsRight and left feetRight and left upper armsRight and left lower armsRight and left hands
Each segment has its own CoM