Final answer:
An object in mechanical equilibrium has no net external force acting on it, and hence it either remains at rest or moves with a constant velocity. The correct answer is Option 1) force, velocity, according to Newton's first law of motion.
Step-by-step explanation:
A mechanical equilibrium refers to the condition in which an object has no net external force acting on it. Considering Newton's first law of inertia, an object at rest will remain at rest, and an object in motion will continue to move at a constant velocity unless acted upon by a net external force. Therefore, the correct answer is that an object in mechanical equilibrium is an object having no net external force, with constant velocity of these. So the answer to the student's question would be Option 1) force, velocity.
Notably, the concept of mechanical equilibrium is essential to understanding forces and motion. When an object is in this state, there is no acceleration, which means the velocity (speed and direction) of the object does not change. Objects at rest are in a state of equilibrium, as are objects that move with constant velocity because the forces acting on them are balanced. This principle is encapsulated in the Newton's first law of motion, also known as the law of inertia.