Four equal masses M are spaced at equal intervals, £, along a horizontal straight rod whose mass can

Four equal masses M are spaced at equal
intervals, £, along a horizontal straight rod whose mass can be ignored. The
system is to be rotated about a vertical axis passing through the mass at the
left end of the rod and perpendicular to it. (a) What is the moment of inertia
of the system about this axis? (b) What minimum force, applied to the farthest
mass, will impart an angular acceleration a l (c) What is the direction of this
force?