A uniform rod is placed vertically on a smooth surface and then released. Then,

Question

A uniform rod is placed vertically on a smooth surface and then released. Then, (A) the centre of rod follows straight line path (B) the centre of mass follows circular path (C) the instantaneous axis is passing through the contact point (D) all the above

Tardigrade Admin · Accepted Answer

Since no external force is present on the rod in horizontal direction, the velocity of the centre of mass of rod, in horizontal direction, remains constant i.e., zero.
So, centre of mass of rod drops vertically downwards.

Q. A uniform rod is placed vertically on a smooth surface and then released. Then,

the centre of rod follows straight line path

the centre of mass follows circular path

the instantaneous axis is passing through the contact point

all the above

Since no external force is present on the rod in horizontal direction, the velocity of the centre of mass of rod, in horizontal direction, remains constant i.e., zero. So, centre of mass of rod drops vertically downwards.

Since no external force is present on the rod in horizontal direction, the velocity of the centre of mass of rod, in horizontal direction, remains constant i.e., zero.
So, centre of mass of rod drops vertically downwards.