Equilibrium of Forces?

Question

What are the conditions that must exist to have forces in equilibrium?

Answer 1

1. The vector sum of all the forces must add up to zero.
2. the sum of clockwise moment should equal to the sum of anticlockwise moment.
3. the vector polygon should be complete and cyclic.

Answer 2

The sum of all vectors must be zero,but this is not enough.The
moment of the system with respect to any point must be also zero.
Ex: take two forces equal and paralel but not on the same line.
The make up to a couple not in equilibrium but their vector sum is 0

Answer 3

The forces must add up to zero, and one way to do this is the third law of motion: for every action there is an equal and opposite reaction. Secondly, the sum of torques must also be zero, so that the object does not rotate.

Answer 4

The vector sum of all the forces must add up to zero.

Answer 5

while the vector sum=0. Laying all the rigidity vectors on the physique head to tail, you get a closed polygon. the 1st rigidity vector starts at "0", so then the vector sum finally ends up at "0".