Understanding Resultant Pressure on Immersed Bodies

The question asks about the specific point within an immersed body where the overall effect of the liquid pressure pushing on it can be considered to act. This resultant pressure force is the sum of all the pressure forces acting on the surface of the body.

Analyzing the Options

Let's look at the provided options and see which one best describes this point:

• Centre of gravity: This is the point where the entire weight of the body is considered to act. It is related to the body's mass distribution, not the external forces from the liquid pressure.
• Centre of buoyancy: This is the point through which the buoyant force acts. The buoyant force is the upward force exerted by the fluid that opposes the weight of a partially or fully immersed object. It is equal to the weight of the fluid displaced by the body and acts through the centroid of the displaced volume. While related to pressure (as buoyancy arises from pressure differences), the question asks for the point where the resultant pressure acts.
• Centre of pressure: This is defined as the point where the resultant hydrostatic force (pressure force) acts on a submerged surface or body. The hydrostatic force is the total force exerted by the fluid pressure on a surface. This point represents the average location of the pressure field on the surface.
• Metacentre: This point is crucial for determining the stability of a floating body. It is the intersection point of the vertical line through the new centre of buoyancy when the body is tilted at a small angle and the original vertical line through the centre of buoyancy. It is not the point of action of the resultant pressure force itself.

Conclusion

Based on the definitions, the point in an immersed body through which the resultant pressure of the liquid may be taken to act is known as the Centre of pressure. This is where the total force due to fluid pressure on the submerged body effectively acts.

Therefore, the correct answer is Centre of pressure.