Q14 of 28 Page 53

The centre of gravity of a body on the earth coincides with its centre of mass for a ‘small’ object whereas for an ‘extended’ object it may not. What is the qualitative meaning of ‘small’ and ‘extended’ in this regard? For which of the following the two coincides? A building, a pond, a lake, a mountain?

Centre of gravity is the point through which the resultant of system of forces (due to weight) of all the particles constituting the body passes for all positions of body.


Centre of mass is a point where whole mass of a body can be concentrated.


When the vertical height of the object is very small as compared to earth’s radius, we call the object small otherwise it is extended.


a) Building and pond are small object so their centre of mass and centre of gravity coincide.


b) Deep lake and mountain are extended objects so their centre of mass doe of mass does not coincide with centre of gravity.


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