Engineering Questions with Answers - Multiple Choice Questions

# Environmental Engineering MCQ – Minimum and Maximum Velocity of Flow

1 - Question

_______ is the velocity at which the solid matter in sewage remained in suspended form.
a) Settling velocity
b) Self cleansing velocity
c) Mean velocity
d) Non Scouring velocity

Explanation: Self cleansing velocity is the minimum velocity, which is required to keep the solid particles in suspended form otherwise they will settle and result in clogging.

2 - Question

The expression for the self cleansing velocity is given by ____________
a) (8*B* (G-1) *g*d/f)1/3
b) (8*B* (G-1) *g*d/f) 2
c) (8*B* (G-1) *g*d/f)
d) (8*B* (G-1) *g*d/f)1/2

Explanation: The self cleansing velocity V is given by V = (8*B* (G-1) *g*d/f) 1/2 Where, G is the specific gravity, g is the acceleration due to gravity, d is the diameter of sewer and f is the Darcy Weisbach friction factor.

3 - Question

The self cleansing velocity required for coarse sand is __________
a) 10cm/Sec
b) 20cm/Sec
c) 30cm/Sec
d) 40cm/Sec

Explanation: The self cleansing velocity required for coarse sand is 20cm/Sec which is higher than fine sand having 15cm/Sec.

4 - Question

In which of the following, the self cleansing velocity is maximum?
a) Angular stones
b) Fine sand
c) Fine clay
d) Fine gravel

Explanation: The self cleansing velocity for angular stones is 100cm/Sec while of fine sand, fine clay and fine gravel are 15cm/Sec, 7.5cm/Sec and 30cm/Sec respectively.

5 - Question

The diameter of the sewer is 23cm. What should be the self cleansing velocity?
a) 10cm/Sec
b) 40cm/Sec
c) 100cm/Sec
d) 130cm/Sec

Explanation: When the diameter of the sewer is between 15cm and 25cm, the self cleansing velocity is 100cm/Sec.

6 - Question

What should be the diameter of the sewer when the self cleansing velocity is 60cm/Sec?
a) 10cm
b) 20cm
c) >60cm
d) 100cm

Explanation: The self cleansing velocity varies inversely with the diameter of the sewer and when the diameter is above 60, the self cleansing velocity is 60cm/Sec whereas, for 15cm diameter of the sewer, it is 100cm/Sec.

7 - Question

The maximum velocity at which no abrasion takes place is called _______
a) Settling velocity
b) Self cleansing velocity
c) Mean velocity
d) Non Scouring velocity

Explanation: The non scouring velocity is the maximum velocity at which no scouring action takes place. It depends on the material used in the construction of sewers.

8 - Question

The non scouring velocity is 260cm/Sec. The type of material of the sewer is __________
a) Earth channels
b) Stone ware sewers
c) Brick lined sewer
d) Cement concrete sewer

Explanation: The non scouring velocity for cement concrete sewer lies between 250cm/Sec to 300 cm/Sec.

9 - Question

The non scouring velocity required for cast iron sewer pipes is __________
a) 50cm/Sec
b) 350cm/Sec
c) 160cm/Sec
d) 220cm/Sec