why different force??

["ahmad_m_eid" <ahmad_m_eid@xxxxxxxxx>]

Dear all 
I use femm in my work in linear generator
when I trace a path around the stator to find the force by "force
from stress tensor" I get a value for the force on stator

when I use the block integration and select all stator blocks anf find
force from " force via weighted stress tensor" I get another value and
away from the first value comes from line integral.

what is the best way to find the force on stator?

how can one explain these different results?