Final answer:
The statement 'If an object is in equilibrium, then any portion of the object that one chooses to examine must also be in equilibrium' is true.
Step-by-step explanation:
The statement, 'If an object is in equilibrium, then any portion of the object that one chooses to examine must also be in equilibrium', is True. In static equilibrium, the object remains either at rest or in uniform motion (both translational and rotational) in a selected inertial frame of reference. This means that the net external force on the object is zero, and as a result, any portion of the object will also have a net force of zero.
For example, if we consider a book placed on a balance scale and balanced by a standard 1-kg iron weight, the scale is in equilibrium. If we change the frame of reference to the moon, where gravity is uniform, the balance is still level and the scale remains in equilibrium.
Therefore, any portion of an object in equilibrium will also be in equilibrium.