The necessary and sufficient condition for a surface to be called as a...
In physics, a free surface is the surface of a fluid that is subject to zero parallel shear stress, such as the boundary between two homogeneous fluids, for example liquid water and the air in the Earth's atmosphere. Unlike liquids, gases cannot form a free surface on their own. So, no stress should be acting on it.
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The necessary and sufficient condition for a surface to be called as a...
Free Surface in Mechanics:
A free surface is a surface which is not in contact with another medium, or is in contact with a medium that is not exerting any stress on it. In mechanics, it is a surface which is not under any stress, and hence any deformation or motion of the surface is solely due to the external forces acting on it.
Necessary and Sufficient Condition:
The necessary and sufficient condition for a surface to be called as a free surface is that no stress should be acting on it. This means that the surface is not under any normal or shear stress, and hence it is not being compressed or stretched in any direction.
Explanation:
When a surface is under stress, it experiences a force per unit area in some direction. If the stress is normal to the surface, then the force is perpendicular to the surface, and if the stress is shear, then the force is parallel to the surface. In either case, the surface is being subjected to a deformation or motion in response to the stress.
However, when there is no stress acting on the surface, then the surface is free to move or deform in any direction based on the external forces acting on it. This is what makes it a free surface.
Conclusion:
In conclusion, the necessary and sufficient condition for a surface to be called as a free surface is that no stress should be acting on it. This condition is important in mechanics, as it helps in analyzing the behavior of surfaces under external forces, and in designing structures that can withstand these forces without deformation or failure.