A stationary uniform rod in the upright position is allowed to fall on a smooth horizontal surface. The figure shows the instantaneous position of the rod. Identify the correct statement. 1) Normal reaction N is equal to Mg 2) N does positive rotational work about the centre of mass 3) A couple of equal and opposite forces acts on the rod 4) All of the above

Options

A. normal reaction N is equal to Mg
B. N does positive rotational work about the centre of mass
C. a couple of equal and opposite forces acts on the rod
D. all of the above.

Explanation

`Mg` can't provide rotatainal motion. This is only `N` which actually provides the rotational motion.