Question

what is couple movement

Answer 1

Couple- Couple is a system created when two equal and opposite forces act on body which results into rotatory motion.
As the net force on body is zero therefore there is no linear motion.

Answer 2

, a particle is in mechanical equilibrium if the net force on that particle is zero. By extension, a physical system made up of many parts is in mechanical equilibrium if the net force on each of its individual parts is zero