Statement (I): Pipes carrying water are anchored at bends and oth
Statement (I): Pipes carrying water are anchored at bends and other points of un- balanced thrusts.
Statement (II): Pipes are anchored by firmly embedding in massive blocks of concrete or masonry to counter side thrusts due to hydrodynamic forces exerted on the joints.A. Both Statements (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
B. Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)
C. Statement (I) is true but Statement (II) is false
D. Statement (I) is false but Statement (II) is true (II) is true:
Please scroll down to see the correct answer and solution guide.
Right Answer is: A
SOLUTION
Let us consider a pipe which is bent at 900.
Before bend water is flowing in horizontal direction and after bend it flow in vertically upward direction. Due to which there is change in momentum of water in both horizontal and vertical direction.
Fx and Fy are the reactions on pipe
ṁ = mass flow rate
Apply impulse momentum equation ‘x’ and ‘y’ directions.
\(\begin{array}{l} {{\vec F}_{net,\;x}} = \dot m\left( {{{\vec v}_{f,\;x}} - {{\vec v}_{i,\;x}}} \right)\\ {P_1}{A_1} - {F_x} = \dot n\left( {0 - {v_1}} \right)\\ \Rightarrow {F_x} = {P_1}{A_1} + \dot m{v_1} \end{array}\)
Similarlly, for ‘y’ direction: Fnet, y = ṁ (vf,y – vi,y)
Fy = P2 A2 = ṁ (v2 – 0)
These Fx and Fy are to be counteracted by proving pipe anchor at bends and other location where this unbalanced thrust occurs.
As per impulse moment equation, net impulse on pipe is equal to its change in momentum. This unbalanced thrust may lead to bursting of pipe and to prevent this pipe bends are anchored and this is done in many ways as shown below:
1. Hydraulic Shock Absorbers
2. Variable spring hangers and supports
3. Embedding in blocks of concrete or masonry
