A static system can be said to be system with forces that act on bodies at rest under equilibrum conditions.
Let's determine the statement that is incorrect.
In a static system, motion do not occur. So, the sum of the forces in all directions of a static system is zero.
For a static system, the y-components and x-components of all external forces tend to sum to zero.
Also, for a static system, the sum of all external force vectors sum to zero.
∑fx = 0
∑fy = 0
Therefore, the statement that is not true for a static system is:
The magnitude of all external force vectors sum to zero.
ANSWER:
The magnitudes of all external force vectors sum to zero.