Does the centre of mass of an object undergoing thermal expansion move? I recently faced the question in an examination. The question is pretty straightforward.
Does the centre of mass of an object undergoing thermal expansion move?

P.S.

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*The solution for this question assumed that centre of mass would not move.

 A: $\vec F_{ext} = M \vec a$ describes the motion of the center of mass (CM), where $\vec F_{ext}$ is the net external force, $M$ is the total mass, and $\vec a$ is the acceleraton of the CM.  With no net external force, the acceleration of the CM is constant; but if the CM has an initial velocity $\vec v$, it is moving and continues moving with constant $\vec v$ with no $\vec F_{ext}$.  The correct answer is the CM will not change velocity; if the velocity is intially zero it will remain zero, but if the initial velocity is not zero it will remain constant and the CM moves with this constant velocity.
A: I think the question is missing an adjective, uniform thermal expansion would not change the center of mass. The way heat is transferred to the body might change the center of mass. Example : a block of butter if heated non uniformly, part of it melting and thus moving the CM due to change of shape.
A: It depends on the composition of the object. If it is made up non-uniformly,of materials with different coefficients of expansion, the center of gravity would move, even if the heat were uniformly distributed.
