Mechanical Engineering - Hydraulics and Fluid Mechanics - Discussion


A water tank contains 1.3 m deep water. The pressure exerted by the water per metre length of the tank is

[A]. 2.89 kN
[B]. 8.29 kN
[C]. 9.28 kN
[D]. 28.9 kN

Answer: Option B


No answer description available for this question.

Suman Biswas said: (Jul 8, 2013)  
We know pressure exerted per unit length = ωH2/2.

So, the pressure of water per metre length = (9. 81x103x1.32) /2.

= 8.29 KN.

Prateek said: (Sep 2, 2016)  
Absolutely right @Suman.

Hema said: (Sep 12, 2016)  
Can anyone explain how that equation comes?

Hartoon said: (Oct 19, 2016)  
@Hema, please refer the book.

Ravindra said: (Nov 17, 2016)  
Pressure diagram is triangular. Base is equal to wh and height h so pressure becomes 1/2 base * height. So pressure becomes wh*h/2.

Amit said: (Feb 12, 2017)  
Thanks for giving the correct explanation.

Vinayak said: (Mar 2, 2017)  
Thank you for giving the solution.

Manish Kumar said: (Mar 4, 2017)  
We know that, pressure= £gh ,where £= density.
Now, pressure exerted by the water (force) = pressure* area = £gh* wh/2 (pre dia is triangular =(1/2)*base*h),

So, pressure exerted per unit lenght(pressure/w) = £gh* h/2 = (1000*9.81*1.3*1.3)/2 = 8.29 kN.

Gupta said: (May 31, 2017)  
Thanks for the explanation.

Narpat said: (Jun 12, 2017)  
Here, w = &rho * g.

Vaibhav said: (Jun 13, 2017)  
Can anyone explain me how that area came?

Vikaah Choudhary said: (Jun 16, 2017)  
Good explanation, thanks @Suman.

Ram said: (Aug 15, 2017)  
Thank you all for the explanation.

Waseem Iqbal said: (Aug 21, 2017)  
Hydraulic force P= rAh'.

Where h' = depth of center of gravity = h/2 in this case.

So P = r (L*h) h/2 = 9.81 * (1.3)^2 /2. ( L cancel out for per meter length).

Arun Kumar said: (Sep 14, 2017)  
Than put,


Naresh said: (Oct 3, 2017)  
Yes right @Arun Kumar.

Here it is not mentioned that tank is a triangular or rectangular or as square tank.

so the pressure at a particular point is given by p=wh^2/2 and density of water is given by pgh.

Jsh said: (Oct 20, 2017)  
Pressure =density *gravity *cg of projected area.
Cg lies at half of height.
Force = pressure * area.
Area = height * length.
Force =ρg(h/2)*h*l.

Sushil Dumka said: (Feb 27, 2018)  
Yes, the answer is right,
8.29 kN.
Pressure diagram becomes triangular and area of triangular is 1/2 wh^2.

Aman Kumar said: (Apr 3, 2018)  
Is it pressure exerted per unit length or pressure force exerted per unit length? Please tell me.

Rakshit Khatri said: (Oct 27, 2018)  
@Aman Kumar.

The pressure exerted by the water per metre length of the tank.

Anomie said: (Feb 2, 2019)  

The pressure cannot have the unit kiloNewton. And the Pressure can only be exerted on an area there is nothing called as the pressure exerted on a unit length.

Niladri Nag said: (Sep 4, 2020)  
Why 1000 is being multiplied with the equation? Anyone explain.

Mohammad Zubair Khan said: (Jan 19, 2021)  
10^3 or 1000 being multiplied to convert the unit from N (Newton) to KN (Kilo Newton).

Abhishek said: (Jul 20, 2021)  
pressure exerted per unit length = ωH2/2.
= (9. 81x103x1.32)/2.
= 8.29 KN.

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