Q3.Ultimate BOD of a river water sample is 20 mg/L. BOD rate constant (natural log) is 0.15 day-1.
The respective values of BOD (in %) exerted and remaining after 7 days are:
Q5.The average surface area of a reservoir in the month of June is 20 km2. In the same month, the
average rate of inflow is 10 m3 /s, outflow rate is 15 m3/s, monthly rainfall is 10 cm, monthly
seepage loss is 1.8 cm and the storage change is 16 million m3
. The evaporation (in cm) in that
month is
Q6.A plane flow has velocity components u = 1/T1, v = -y/T2 and w = 0 and x, y and z directions
respectively, where T1 (≠0) and T2 (≠0) are constants having the dimensions of time. The
given flow is incompressible if
Q7.Group I lists a few devices while Group II provides information about their uses. Match the
devices with their corresponding use.
Answer : Option DExplaination / Solution:
Aneometer → wind speed
Hygrometer → water vapour content of air
Pilot tube → flow velocity at a specific point in the flow stream
Tensionmeter → Capillary potential of soil water
Q8.A venturimeter having a throat diameter of 0.1 m is used to estimate the flow rate of a
horizontal pipe having a diameter of 0.2 m. For an observed pressure difference of 2 m of
water head and coefficient of discharge equal to unity, assuming that the energy losses are
negligible, the flow rate (in m3 /s) through the pipe is approximately equal to
Q9.With reference to a standard Cartesian (x, y) plane, the parabolic velocity distribution profile
of fully developed laminar flow in x-direction between two parallel, stationary and identical
plates that are separated by distance, h, is given by the expression
In this equation, the y = 0 axis lies equidistant between the plates at a distance h/2 from the
two plates, p is the pressure variable and µ is the dynamic viscosity term. The maximum and
average velocities are, respectively
Q10.A waste water stream (flow = 2 m3 /s, ultimate BOD = 90 mg/l) is joining a small river (flow
= 12 m3 /s, ultimate BOD = 5 mg/l). Both water streams get mixed up instantaneously. Crosssectional
area of the river is 50 m2 . Assuming the de-oxygenation rate constant, k' = 0.25/day,
the BOD (in mg/l) of the river water, 10 km downstream of the mixing point is
Answer : Option CExplaination / Solution:
Total Question/Mark :
Scored Mark :
Mark for Correct Answer : 1
Mark for Wrong Answer : -0.5
Mark for Left Answer : 0