Civil Engineering - Hydraulics - Discussion

Discussion Forum : Hydraulics - Section 1 (Q.No. 5)
5.
If the atmospheric pressure on the surface of an oil tank (sp. gr. 0.8) is 0.1 kg/cm2, the pressure at a depth of 2.5 m, is
1 metre of water
2 metres of water
3 metres of water
3.5 metres of water
4.0 metres of water.
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
42 comments Page 2 of 5.

Amare yihunie said:   7 years ago
Specific gravity oil = 0.8.

Density of oil=0.8*1000=800 kg/m3
Atmospheric pressure at surface of oil=0.1 kg/cm2=0.1*10000*10=20,000 pascal
Pressure of oil at depth of 2.5 m = 800 * 2.5 * 10 = 10,000 pascal.

Total pressure = 10,000 + 20,000 = 30000 pascal.

In terms of water depth pressure = density of water * depth of water * gravity.

The Depth of water = pressure/density * gravity = 30,000/(10000*10) = 3 meter.
(1)

Nani Abdul said:   7 years ago
Patm + (0.8)(2.5m)(9810N/m3) = Hh2o(9810N/m3).

Patm = 0.1Kg/cm2 --> 1000Kg/m2.
Patm = 1000Kg/m2(9.81m/s2) --> 9810N/m2 (Pa).

9810N/m2 + (0.8)(2.5m)(9810N/m3) = Hh2o(9810N/m3).
Hh20 = (9810N/m2 + (0.8)(2.5m)(9810N/m3))/9810N/m3.
Hh20 = 3mts.
(1)

Komala sai said:   9 years ago
Patm = 0.1kg/cm^2
=> 1000kg/m^2.

Poil = (0.8 * 1000) * 2.5
= 2000 kg/m^2.

Finally in terms of water = (1000 + 2000) ÷ 1000,
= 3m of water.
(1)

Ccjayesh said:   10 years ago
Pa = 0.1 kg/cm2 = 1000 kg/m2.

Poil = 800*2.5 = 2000 kg/m2.

Total = 3000 kg/m2 = 3000/1000 = 3 meters of water.

Kanishk said:   1 decade ago
How come the answer is C?

Initial Pressure in terms of ht. of water column= 1000/(1000*10)=0.1 m --- (i).

Pressure @ 2.5 m depth in oil tank = 2.5*800*10.

Representing above pressure as ht of water column, the answer comes out to be 2.0 m --- (ii).

(i) + (ii) = 2.1m.

Hitesh kumar said:   1 decade ago
Total pressure = ((.1*10^4)/1000)+(.8*2.5) = 3.

KUMAR said:   1 decade ago
Initial pressure is 1000 kg/m^2.

Pressure at 2.5 m depth is 19620 kg/m^2.

Total pressure at a depth 2.5 m is = 19620+1000 = 20620 kg/m^2.

Depth in terms of water = 20620/(1000*9.81) = 2.1 m.

Ruben said:   1 decade ago
From Basic Hydro static principle (FM text book by Frank m White).

P = Pa-Gamma (Z2-Z1).

Where Pa = Atmospheric pressure in n/m2 Z1 = 0 (Reference surface) and Z2 = negative downwards.

= (0.98 n/m2-7848(-2.5)).

= 19620.8 pa.

H = (19620.8/(1000*9.81)) = 2 m of water.

Nikita patil said:   1 decade ago
How do you calculate the pressure at the given height? Please explain me.

Manpraveen said:   1 decade ago
P = $gh.

Pressure for oil = 0.8*1000*9.81*2.5 = 19620 n/m^2.

Pressure for water = 1000*9.81*h = 19620.

H1 = 19620/9810 = 2 m.

H2 = atmospheric head = p/$g.

H2 = 1000*9.81/1000*9.81= 1 m.

Total head = H1+H2 = 2+1 = 3 m (Answer).


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