This set of Fluid Mechanics Questions and Answers for Entrance exams focuses on “Classification of Orifice & Hydraulic Coefficients”.
1. When is orifice called ‘large orifice’?
a) If the head of liquid is less than 5 times the depth of orifice
b) If the head of liquid is less than 2.5 times the depth of orifice
c) If the head of liquid is less Hence, 4 times the depth of orifice
d) If the head of liquid is less than 1.5 times the depth of orifice
View Answer
Explanation: It is the correct parametric definition for ‘large orifice’.
2. In case of any orifice, velocity always remains constant and hence discharge can be calculated.
a) True
b) False
View Answer
Explanation: In case of large orifice, velocity always remains variable and hence discharge cannot be calculated.
3. Find the discharge through a rectangular orifice 2.2 m wide and 1.3 m deep fitted to a easier tank. The water level in a team is 2.5 m above the top edge of orifice.
a) 13.9 m3/s
b) 11.5 m3/s
c) 16.9 m3/s
d) 8.7 m3/s
View Answer
Explanation: Q = 2/3 Cd *b*√2g* (H21.5 – H11.5)
Here,
H1 = 3.8
H2 = 2.5
b = 2.2
Hence, Q = 13.9 m3/s.
4. Find the discharge through a rectangular orifice 3.2 m wide and 1.7 m deep fitted to a easier tank. The water level in a team is 3.3 m above the top edge of orifice. Take Cd = 0.6
a) 29.4 m3/s
b) 58.5 m3/s
c) 67.9 m3/s
d) 78.7 m3/s
View Answer
Explanation: Q = 2/3 Cd *b*√2g* (H21.5 – H11.5)
Here,
H1 = 5
H2 = 3.3
b = 3.2
Hence, Q = 29.4 m3/s.
5. Find the discharge through totally drowned orifice of width 2.3 m if the difference of water levels on both side of the orifice be 40 cm. The height of water from to and bottom of the orifice are 2.6 m and 2.75 m respectively.
a) .56 m3/s
b) .64 m3/s
c) .75 m3/s
d) .55 m3/s
View Answer
Explanation: Q = Cd * b * (H2 – H1) √2gH
Here, b = 2.3
H2 = 2.75
H1 = 2.6
H = 40
Q = .56 m3/s.
6. Find the discharge through totally drowned orifice of width 3.3 m if the difference of water levels on both side of the orifice be 50 cm. The height of water from to and bottom of the orifice are 2.25 m and 2.67 m respectively.
a) 2.8 m3/s
b) 2.7 m3/s
c) 2.6 m3/s
d) 2.5 m3/s
View Answer
Explanation: Q = Cd * b * (H2 – H1) √2gH
Here, b = 3.3
H2 = 2.67
H1 = 2.25
H = 50
Q = 2.6 m3/s.
7. A rectangular orifice of 2 m width and 1.2 m deep is fitted in one side of large tank. The easier level on one side of the orifice is 3m above the top edge of the orifice while on the other side of the orifice the water level is 0.5 m below it’s top edge. Calculate discharge if Cd = .64
a) 4.95 m3/s
b) 5.67 m3/s
c) 3.56 m3/s
d) 6.75 m3/s
View Answer
Explanation: Explanation: Q = Cd * b * (H2 – H) √2gH
Here, b = 2
H2 = 4.2
H = 3.5
Q = 4.94 m3/s.
8. The time taken to empty the tank is independent of Cd but depends only on the height and acceleration due to gravity.
a) True
b) False
View Answer
Explanation: The time taken to empty the tank is dependent on Cd as well as depends only on the height and acceleration due to gravity.
9. The discharge rate is independent of the height difference and dependent only on the height.
a) True
b) False
View Answer
Explanation: The discharge rate is dependent of the height difference and dependent only on the height.
10. In case of submerged orifice the discharge is substantially dependent on temperature of fluid
a) True
b) False
View Answer
Explanation: Discharge is dependent on temperature but minimally.
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