Question
State the characteristics of centre of mass.
✓
Answer
- Centre of mass is a hypothetical point at which entire mass of the body can be assumed to he concentrated.
- Centre of mass is a location, not a physical quantity.
- Centre of mass is particle equivalent of a given object for applying laws of motion.
- Centre of mass is the point at which applied force causes only linear acceleration and not angular acceleration.
- Centre of mass is located at the centroid, for a rigid body of uniform density.
- Centre of mass is located at the geometrical centre, for a symmetric rigid body of uniform density.
- Location of centre of mass can be changed only by an external unbalanced force.
- Internal forces (like during collision or explosion) never change the location of centre of mass.
- Position of the centre of mass depends only upon the distribution of mass, however, to describe its location we may use a coordinate system with a suitable origin.
- For a system of particles, the centre of mass need not coincide with any of the particles.
- While balancing an object on a pivot, the line of action of weight must pass through the centre of mass and the pivot. Quite often, this is an unstable equilibrium.
- Centre of mass of a system of only two particles divides the distance between the particles in an inverse ratio of their masses, i.e., it is closer to the heavier mass.
- Centre of mass is a point about which the summation of moments of masses in the system is zero.
- If there is an axial symmetry for a given object, the centre of mass lies on the axis of symmetry.
- If there are multiple axes of symmetry for a given object, the centre of mass is at their point of intersection.
- Centre of mass need not be within the body.
Example: jumper doing fosbury flop.
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