Question

In which condition torque
can be balanced by single force

Answer 1

Torque can be balanced by a moment of force F, in the opposite direction.

The moment of force about the axis of rotation of the object, is in the direction opposite to the given Torque (or angular acceleration), and  r Χ F = - Torque or = - I α
     r = perpendicular distance of Force vector from the axis of rotation of object

            F = -Torque / r Sin Ф, = - I α / r Sin Ф,      where Ф is the angle between r and F.
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Suppose L is the axis about which the torque is calculated.  Let I be the moment of inertial of the body. Let α be the angular acceleration of the object under the influence of torque.  T = I α 

Suppose the torque is  caused by a force or many forces with the total of couple of moments = T = Σ r Χ Fi

Let the force F be at a distance r from the axis of rotation of object, or the direction of T.  

      T = - r Χ F