Question

the resultant force of a couple is zero but the resultant of a couple is not zero.some body tell me with example

Answer 1

take a long rod .
apply force on one corner downwardly .
apply another force of equal magnitude that of 1st force on other corner upwardly.
since both forces are equal and are acting in opposition directions resultant couple of force is 0.
but resultant couple is not 0 because the rod will move due to torque .