if the alpha is larger than 90 degree ( which means the resultant F is lean towards -x axis , then the angle between the Ax and the line from Ax to A will be less than 90 , am i right ?
If the force is lean towards negative x axis , it means the angle between the force and positive x -axis is more than 90 degree, right ? then how is it possible for it to remain 90 degree?No. It will be exactly 90##^\circ##
(the 90##^\circ## as indicated in figure 2-26 (a) )
ya , i mean the line from Ax to A, not about the line from the origin to A (i.e. A⃗ itself).You were talking about the line from Ax to A, not about the line from the origin to A (i.e. ##\vec A## itself).