question_answer 45)

                  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?                

Answer:

                  Small object means an object whose dimensions are negligible as compared to the radius of earth. Extended object means an object whose dimensions are not negligible as compared to the radius of earth.                 Centre of gravity coincides with the centre of mass in case of a building and a pond.