Equilibrium of Rigid Body
o A force changes the translational state of the motion of the rigid body, i. e. it changes its total linear momentum.
o A torque changes the rotational state of motion of the rigid body, i. e. it changes the total angular momentum of the body
Note: Unless stated otherwise, we shall deal with only external forces and torques.
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A rigid body is said to be in mechanical equilibrium, if both its linear momentum and angular momentum are not changing with time. This means
Total force should be zero => Translational Equilibrium Total torque should be zero => Rotational Equilibrium