Question

A mercury thermometer is placed in a gravity free half without touching. As temperature rises mercury expands and ascend in thermometer. If height ascend by mercury in thermometer is h then by what height centre of mass of mercury and thermometer system descend?

Answer 1

Here thermometer is placed in gravity free region.

So there is no external force on the system.

When there is no force on the system its center of mass will retain its position and does not move if the whole system is initially at rest.

So here the displacement of center of mass of the system will be ZERO.