Rotational Motion Question 85
Question: Point masses and are placed at the opposite ends of a rigid rod of length L and negligible mass. The rod is to be set rotating about an axis perpendicular to it. The position of point P on this rod through which the axis should pass, so that the work required to set the rod rotating with angular velocity is minimum, is given by
Options:
A)
B)
C)
D)
Show Answer
Answer:
Correct Answer: D
Solution:
-
As two point masses
and are placed at opposite ends of a rigid rod of length L and negligible mass .Total moment of inertia of the rod
As,
is minimum i.e.When
is minimum, then work done on rotating a rod with angular velocity will be minimum.Shortcut Way The position of point P on rod through which the axis should pass, so that the work required to set the rod rotating with minimum angular velocity
is their centre of mass, we have