Civil Engineering - Hydraulics - Discussion

2. 

A cylindrical vessel 40 cm high is revolved about its vertical axis so that the water touches the bottom when it just spills out. If the radius of the cylinder is 5 cm, the angular velocity of rotation, is

[A]. 2 rad/sec
[B]. 3 rad/sec
[C]. 4 rad/sec
[D]. 5 rad/sec
[E]. none of these.

Answer: Option A

Explanation:

No answer description available for this question.

Vaish said: (Nov 16, 2015)  
(4*g*h/3).

Abhi said: (Mar 19, 2016)  
y = yo + [(ω^2 x r^2)/(2 x g)].

0.4 = 0 + [(ω^2 x r^2)/(2 x g)].

0.4*2*9.81/0.05 = ω^2.

ω = 12.52 rad/sec.

M.S.Bainsla said: (Dec 25, 2016)  
2 rad/sec is correct. I agree.

Priya said: (May 12, 2017)  
Please explain it clearly.

Mrutyunjay said: (May 31, 2017)  
How? Please explain.

Arun said: (Aug 21, 2017)  
How 2rad/sec is correct? Explain.

Anurag said: (Feb 19, 2018)  
Explain how.

Priya said: (Mar 21, 2018)  
It should be (4/3*g*h).

Anshu said: (Jun 14, 2018)  
√ ((0.4*2*9.81)-0.05) = 2.79.

Hence answer is A correct.

Rohit said: (Jul 12, 2018)  
(4/3 * r * h) * 3.14/180.

Putting the values;

4/3 * 40 * 2.23 * 3.14/180.
= 2.08 rad/sec.

Shubham said: (Jul 26, 2018)  
Formula is.

Vessel height =( angula velocity"2 * radius"2)/2g.

Deepak said: (Nov 6, 2018)  
According to me, it is 125.28 radian/sec.

Anurag said: (Feb 2, 2019)  
12.52 rad/sec is the right answer.

Vasudev said: (Jul 16, 2019)  
I also got 12.52. Here h equals 40 cm equals omega square x r square which is 5 cm divided by 2x 10 m per sec square.

Muhammad Saqib said: (Sep 20, 2019)  
Explain how 2rad/sec correct? Please explain me.

Lalit Pathade said: (Oct 17, 2019)  
Vessel height =( angula velocity^2 * radius^2)/2g.
(40) =(angular velocity ^2 * (sqrt(5)) ^2) /(2*9.81).
Angular velocity = 2rad/sec.

Kiran said: (Feb 17, 2020)  
@ Deepak. You are close to the answer. Just covert the units. 125.28 is in rad/min. Divide by 60 to get 2 rad/sec.

12.28/60 ~ 2 rad/sec.

Kanya said: (Feb 19, 2020)  
@Kiran, 12.28รท60 = 0.2 not 2.

Sunil Padhy said: (May 6, 2020)  
We know,

If a cylinder is rotated with constant angular velocity (v)by the application of external torque. It is called forced vortex motion (V).

Or H = (v^2 x R^2 )/(2g).
Then v= π{2gH/( R^2)}.
To get rad/sec multiple (π/180).

Slr said: (Dec 1, 2020)  
Correct ans is 125.28 rad/sec.

Equate all in meters for ease.
The equation is:
H - y(min) = (w^2 x R^2)/(2g)
So, here y(min) =0.
Therefore 0.4 = (w^2 x .0005)/(2 x 9.81)
Solve it, you directly get an answer in rad/sec. There's nothing to convert.
After solving. w= 125.28 rad/sec.

You need to convert to rad/sec if you get an answer in degree.
180°= π rad/sec
1°= π/180 rad/sec.

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