Question

A body is said to be in static Equilibrium
(A) When it is moving around a circular path
(B) When it is at rest
(C) When it is moving with uniform velocity
(D)When it is accelerated by external force

Answer 1

Equilibrium means a body is either at rest or in a uniform motion. For this first consider an inertial frame of reference which doesn’t have translational and rotational motion, then the body is said to be in static equilibrium. At equilibrium the total external force acting on a body is equal to zero and external torque also must be zero.

Complete answer:
The word static means stationary. Thus the static equilibrium is attained when an object is at rest. The forces acting on the object should also be considered in this case. Thus the vector sum of all forces acting on an object is zero in static equilibrium. According to Newton’s law of motion, the object in rest continues to be in rest and the object in motion always continues in motion.
Static equilibrium and dynamic equilibrium are two forms of equilibrium. Where static represents objects in rest and dynamic equilibrium represents objects in motion. That is, in a uniform velocity. These are the two branches of mechanics. In all these cases the total forces acting on the object will be zero.

Hence option (B) is correct.

Note:
The word static means stationary. Thus the static equilibrium is attained when an object is at rest. Equilibrium means a body is either at rest or in a uniform motion. For this first consider an inertial frame of reference which doesn’t have translational and rotational motion, then the body is said to be in static equilibrium. At equilibrium the total external force acting on a body is equal to zero and external torque also must be zero.