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.

Pawan pandey said:   5 years ago
0.1*10^4 kg/m2= 1000 kg/m2.
0.8*1000*2.5= 2000 kg/m2,
1000+2000= 3000 kg/m2 ( pressure ),
3000/1000= 3 m of water.

Ravinder said:   5 years ago
Patm=0.1kg/cm^2=10,000Kg/m^2.
Pressure at 2.5m=0.8*1000*0.8*2.5=19620Kg/m^2.
Total pressure at 2.5m=10,000+19620=29620Kg/m^2.
But in option, we need pressure in terms of head=Pressure/(Density*g)
H=29620/(9.81*1000)=3.1~3m of water column.

Saurabh kaday said:   5 years ago
Don't understand clearly.

Anyone, please solve it by standard formula with step by step with meaning.

Govind said:   5 years ago
The pressure at the bottom is 2.5x0.8x9.81= 19.62 KN/M3.
Initial pressure at top= 0.1 kg/cm2= 0.1x98.06=9.80 KN/M3.
Total pressure at Bottom =19.62+9.80 =29.42 KN/M3.
Head= 29.4/9.81 =2.99 =3.00 Metre.
(1)

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)

Prashant said:   7 years ago
How (total pressure/atm pressure) is equal to the pressure head of water?

Please explain anyone.

Thanks.

WAQAR AHMED AWAN said:   8 years ago
We know that;

1kg=9.81N and 1m=100cm.
let atmosppheric pressure at top surface be; P1=denssity*g*h=0.1kg/cm2=0.1*9.81*100*100=9810N/m2.
let pressure at heigt of 2.5m be p2=0.8*1000*9.81*2.5=19620N/M2.
now total pressureP =p1+p2=9810+19620=29430N/m2.
NOW pressure in terms of water =P/p1=29430/9810=3m so option C is correct.

Gurmeet said:   8 years ago
Simply P = density * gh.

Suresh yadav said:   8 years ago
Yes, your answer is correct. Thank you @Dipesh.


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