Question

A uniform rod is kept vertically on a horizontal smooth surface at a point O. If it is rotated slightly and released, it falls down on the horizontal surface. The lower end will remain

(a) at O
(b) at a distance less than l/2 from O
(c) at a distance l/2 from O
(d) at a distance larger than l/2 from O.

Answer 1

Answer ⇒ Option (c) . ''At a distance l/2 from O''.

Explanation ⇒ According to the question, the rod is uniform therefore its Center of mass will be in the middle or at the centre i.e. at l/2 distance from the ends.

Now, When the rod is vertical the Centre of the mass will be l/2 distance where l is the length of the rod, vertically above the point O.

Since there is no force in the horizontal direction therefore the centre of the mass will be on the point O, after it falls down.

Hence the lower end will remain at a distance l/2 from O.

Hence, Answer is Option (c).

Hope it helps.