A force of -F k acts on O , the origin of the coordinate system. The torque about the point (1,-1) is

Step-by-step solution

Position vector ( r = PO = O -(1 i -1 j )=- i + j ) Torque about point (P, = r F ) ( aligned & =(- i + j ) (-F k ) & OR =F[( i k )-( j k )]=F[- j - i ] & =-F[ i + j ] aligned )