Two small circular ofifices of diameters d1 and d2 are placed on one s...
Solution:
Given,
d1 = diameter of the first orifice = ?
d2 = diameter of the second orifice = ?
h1 = depth of the first orifice = 25 cm = 0.25 m
h2 = depth of the second orifice = 1 m
Let us consider the Bernoulli's equation between section 1 and 2 as shown in the figure below.
Where,
v1 and v2 are the velocities of water at sections 1 and 2 respectively.
p1 and p2 are the pressures at sections 1 and 2 respectively.
z1 and z2 are the elevations of sections 1 and 2 respectively.
hf is the head loss due to friction.
g is the acceleration due to gravity.
As the water level in the tank is constant, the pressure at section 1 and 2 will be atmospheric pressure. Therefore,
p1 = p2 = atmospheric pressure
Also, the head loss due to friction can be neglected as the orifices are small.
Thus, the Bernoulli's equation reduces to:
v1^2/2g + z1 = v2^2/2g + z2
As the discharge through both the orifices is the same, we have:
v1A1 = v2A2
Where,
A1 = cross-sectional area of the first orifice = πd1^2/4
A2 = cross-sectional area of the second orifice = πd2^2/4
Substituting the values of A1 and A2 in the above equation, we get:
v1d1^2 = v2d2^2
Substituting this in the Bernoulli's equation, we get:
d1^2/d2^2 = h2/h1
Substituting the given values, we get:
d1^2/d2^2 = 4
Taking the square root of both sides, we get:
d1/d2 = 2
Therefore, the ratio of the diameters d1 and d2 will be 2:1. Hence, option (C) is the correct answer.