The net force on a body is the resultant of all the force acting on the body, which can be calculated by the vector addition of all the forces as the force is a vector quantity.
Generally, the components of the forces in a single direction (x,y, and z) added together, then the resultant of all the forces can be determined which is the net force.
For example if f1, f2,..fn are n forec action on the body as
f1 = a1 i + b1 j + c1 k
f2= a2 i + b2 j + c2 k
fn = an i + bn j +cn k
Then the net force, F, action on the body
F= f1 + f2+ ... +fn
F= (a1 i + b1 j + c1 k) + (a2 i + b2 j + c2 k)+...+(an i + bn j +cn k)
F=(a1+a2+...an)i+(b1+b2+...+bn)j + (c1+c2+...+cn)k which is the net force.
In this way, the net force can be determined.
