“A state of balance where the net force and torque acting on an object or system is zero is called Equilibrium.”
There are two types of equilibrium.
| Static Equilibrium | Dynamic Equilibrium |
|---|---|
| A state in which the sum of forces acting on an object is equal to zero and its velocity is zero. | A state in which the net forces acting on an object are balanced, but its velocity is not necessarily zero. |
| An object hanging at rest from a string, balanced weight on a scale. | An object moving with a constant velocity, a spinning top. |
| No acceleration and the net force is zero. | No net force and the acceleration is zero. |
There are three states of equilibrium given as
| Stable Equilibrium | Unstable Equilibrium | Neutral Equilibrium |
|---|---|---|
| The body is said to be in stable equilibrium if when slightly displaced and then released it returns to its previous position. | The body is said to be in unstable equilibrium when slightly tilted and does not return back to its previous position. | The body is said to be in neutral equilibrium when displaced from the previous position and remains in equilibrium in the new position. |
| A body is in stable equilibrium when: - Its Centre of gravity is at its lowest position - When it is tilted its Centre of gravity rises - It returns back to a stable state by lowering its Centre of gravity |
A body is in unstable equilibrium when: - Its Centre of gravity is at the highest position. - When it is tilted its Centre of gravity is lowered - Its previous position cannot be restored by raising |
A body is said to be in neutral equilibrium when: - Its Center of gravity always remains above the point of contact. - When it is displaced from its previous position it's Centre of gravity remains at the same height. - All the new states in which the body is moved are stable states. |
Stability refers to the ability of an object or system to remain balanced or unchanged in its position, state, or behavior over time.
In most situations, we are interested in maintaining stable equilibrium, or balance. For example, the Design of structures, racing cars, and in working with the human body. Consider a refrigerator if it is tilted slightly it will return back to its original position due to torque on it. But if it is tilted more it will fall down. The critical point is reached when the centre of gravity shifts from one side of the pivot point to the other. When the centre of gravity is on one side of the pivot point, the torque pulls the refrigerator back onto its original base of support If the refrigerator is tilted further, the centre of gravity crosses onto the other side of the pivot point and The torque causes the refrigerator to topple.