Question

The center of pressure of surface subjected to fluid pressure is the point
A. on the surface at which resultant pressure acts
B. on the surface at which gravitational force acts
C. equal to volume of liquid displaced
D. none

Answer 1

From the question itself it is very clear that the centre of pressure is basically a point and hence option C doesn’t make any sense. The very name of the point suggests that it should be related to resultant pressure. Now if we know the location on which the resultant pressure acts we will get the answer.

Complete answer:
In the question, we are asked to determine where the point called the centre of pressure of the surface that is subjected to fluid pressure is located.
The point on which the total sum of a pressure field acts on a body is called the center of pressure. This results in a force to act through that point. The value of the integrated vectorial pressure field gives the total force vector acting at the center of pressure. Equivalent force and moment on the body is produced as the original pressure field by the resultant force and the centre of pressure location. In general, the centre of pressure is found to be located on the body. However, it is also possible for it to be present on the outside of the body as in fluid flows there is a chance for the pressure field to exert a moment on the body of such magnitude.
Therefore, we could say that the center of pressure of the surface subjected to fluid pressure is the point on the surface at which resultant pressure acts.

So, the correct answer is “Option A”.

Note:
The centre of pressure is analogous to centre of gravity as it is the average location of pressure variation while center of gravity is the average location of weight of an object. It is most important in any flying object. We have to know the location of the centre of pressure to trim a plane or even to provide stability for a model rocket or a kite.