Balancing of Multiple Mass in Single Plane

The single plane balancing is applicable only to thin disks or rotors where unbalance is only
Balancing of rotating and reciprocating parts of an engine is necessary when it runs at
Balancing is a method of correcting or eliminating unwanted inertia forces and couples in rotating and reciprocating parts of the machine
A system of rotating masses is said to be in dynamic balance if any resultant centrifugal force or couple does not exist.
A rigid body is in equilibrium if
Which of the following factors are not responsible for unbalancing in rotating systems?