The incorrect statement about an object in equilibrium is that 'the object must be at rest.' Objects in dynamic equilibrium can be moving with a constant velocity while still being in a state of equilibrium.
The question pertains to the physical concept of equilibrium, particularly as it relates to forces acting on an object. When an object is said to be in equilibrium, this can occur in two possible states: static equilibrium or dynamic equilibrium. In static equilibrium, an object is at rest and no net external forces are acting on it.
On the other hand, dynamic equilibrium describes a situation where an object is moving with a constant velocity, which also means no net external force is acting on it, and the object has no acceleration.
Therefore, the statement that is not true for an object in equilibrium is that 'the object must be at rest.'
An object in equilibrium may be moving at a constant velocity and still satisfy the conditions of equilibrium.