- #1

kachi

- 9

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## Homework Statement

A circular viewing window of diameter D = 0.4m is placed in the Holding tank. The top of the window is H = 1.2m below the water surface. Find the hydrostatic force acting on the window and locate the corresponding centre of pressure (CP).

There is a diagram attached to the question. I have attached a file with the diagram (hydrostaticq.png).

## Homework Equations

Pressure (kPa):

p = ρ x g x h

ρ density of water at 20 degrees celsius (kg/m^3)

g acceleration due to gravity (m/s^2)

h height (m)

Force (KN):

F = p x A

where,

p = pressure (Pa)

A = area (m^2)

## The Attempt at a Solution

Given:

- Window has a diameter of 0.4m

- Top of window height measures 1.2m

Find:

Hydrostatic force acting on window

Centre of pressure (CP)

Pressure (kPa):

p = ρ x g x h

ρ density of water at 20 degrees celsius = 998 kg/m^3

g acceleration due to gravity = 9.81 m/s^2

h height = 1.2m

Force (KN):

F = p x A

where,

p = pressure

A = area = pi(diameter)^2/4 = pi(0.4m)^2/4= 0.12566m^2

---

p = 998 kg/m^3 x 9.81 m/s^2 x 1.2m

= 11748.456 N/m^2

= 11.75 kPa

F = 11.75 kPa * 0.12566 m^2

= 1.476 KN

**Hydrostatic force acting on window is 1.476 KN**

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Is this correct?

Can someone please explain to me in simple English what Hydrostatic force is? What are some real-life examples of where I can see Hydrostatic force? For example, according the problem above is hydrostatic force, the force from water inflicted on the viewing window?

Also with the center of pressure, can you also please clarify what the 'centroid' and the 'centre of pressure' are? I have a slight understanding of what they are but not that much...

**Locate the centre of pressure:**

Would the centroid be located at the middle of the viewing window? Would the center of pressure be located on the middle of one side of the centroid? I have an image attached where I've marked the points. (hydrostaticq2.png).Thank you in advance for your help. I appreciate it!