How can we prove that the forces acting on a body can form a closed-up

[asdff529]

How can we prove that the forces acting on a body can form a closed-up polygon?

 

[McLaren Rulez]

If they didn't, then there would be a resultant force. The magnitude of the resultant is zero only if the other forces form a closed polygon. The condition for equilibrium is, of course, no net force

 

[JHamm]

If there are no forces or only two forces on the object then that object could be in equilibrium but the force vectors can't be connected to form a polygon.

 

[McLaren Rulez]

Well you could think of the two forces case as going along a line and back along the same line.

The idea to remember is that the sum of the force vectors is a zero vector for the object in equilibrium.