Toppling of cylinder containing fluid

1. Mar 9, 2014

Tanya Sharma

1. The problem statement, all variables and given/known data

A light cylindrical vessel of radius r is kept on a rough horizontal surface with sufficient friction so that it cannot slide but can topple. It is filled with water up to a height 2h and a small hole of area a is punched in it so that the water coming out of it falls at the maximum distance from its wall along horizontal surface. Water comes out horizontally from the hole. The value of h for which the cylinder topples is (are)

A)πr3/2a
B)2πr3/a
C)3πr3/2a
D)4πr3/3a

2. Relevant equations

3. The attempt at a solution

Using Bernoulli's principle ,velocity of the fluid coming out of the hole v= √(2gy) where y be the distance of the hole from the top .

Now since water coming out of it falls at the maximum distance from the cylinder wall along horizontal surface ,we need to maximize the distance S = (√(2gy))(√(2(2h-y)/g) .

From this we get y=h

Water coming out of the hole gives an impulse Fdt = (dm)v to the rest of the fluid ,where dm = ρA(dx)

Fdt = ρA(dx)v
or F = ρAv2

If the block has to topple about the rightmost point P , then there has to be a net torque about that point.

i.e ρAv2h - ρπr2(2h)gr ≥0

or 2ρgAh2≥2ρgπr3h

or h≥πr3/A

But this is none of the given options .

I am not sure if my reasoning and approach is correct .

I would be grateful if somebody could help me with the problem .

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Last edited: Mar 9, 2014
2. Mar 10, 2014

BvU

Completely agree with you, but the formulation of the question apparently allows multiple answers....
(a bit corny way of detracting good students, this question!)

3. Mar 10, 2014

phoenixXL

So,are all the three (b), (c) and (d) correct ?

4. Mar 10, 2014

Tanya Sharma

Thanks for the input.

5. Mar 14, 2014

Tanya Sharma

Would someone like to give opinion on my work in post#1 ?

6. Mar 14, 2014

BvU

Apart from that it's excellent ? I would go with XL and circle b, c and d.
If only I could regain my credibility again....

7. Mar 16, 2014

Thanks BvU