Rotating cone filled with water

AI Thread Summary
The discussion revolves around determining the optimal position to drill a hole in a rotating cone filled with water to maximize the distance the water sprays. The user applies the Bernoulli equation to derive the velocity of water at the hole, considering factors like height and rotation. There is uncertainty about whether the Bernoulli equation is correctly applied, particularly regarding the incorporation of rotational velocity. The user also explores using Lagrange multipliers to solve the problem but struggles with the calculations. The conversation highlights the influence of cone shape on spray distance and the complexities of fluid dynamics in a rotating system.
largich
Messages
2
Reaction score
0
I have a cone filled with liqid with radius R and height H rotating with \omega. Where do we have to drill a hole that the water would spray to the maximum distance from the cone?

I used the Bernoulli equation obtainig
p_0+0.5 \rho {v_1}^2=p_0+0.5 \rho v^2
v is the speed at the hole, getting

v^2=2g(H-h-h^2-r^2\frac{\omega^2}{2g})=2g(H-h-h^2\frac{(tg{\alpha})^2}\omega^2}{2g}),
where tg{\alpha}=R/H.
I taught using Lagrange multiplicator, where the constraint is the water falling on the floor prom the upward cone:

\psi=v sin{\alpha} t+gt^2/2-h=0.

Further more:
F=v_x t+\lambda(v sin{\alpha} t+gt^2/2-h)
=v cos{\alpha}+\lambda(v sin{\alpha} t+gt^2/2-h)
Solution should be obtained by
\frac{\partial F}{partial t} and

\frac{\partial F}{partial v}, v=v(h),
but i can't solve it.
Did I make the concept wrong? Any ideas would be helpfull.

PS: The cone is standing on its tip and it is opened at the top.
 
Physics news on Phys.org
Two things will help to spray that water; the pressure which increases as we go down the cone, and the angular momentum which increases as we go up the cone. With a very flat cone I should imagine the best place is near the top; With a very sharp cone I guess the best place is near the bottom. There should be an angle at which it doesn't matter.
 
Thank you. I agree. But the problem is solving the equation. Is the use of Bernoulli eq. even correct. Do I incorporate the rotation velocity in Bernoulli eq. or as a separate contribution?
 
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Struggling to make relation between elastic force and height'
Hello guys this is what I tried so far. I used the UTS to calculate the force it needs when the rope tears. My idea was to make a relationship/ function that would give me the force depending on height. Yeah i couldnt find a way to solve it. I also thought about how I could use hooks law (how it was given to me in my script) with the thought of instead of having two part of a rope id have one singular rope from the middle to the top where I could find the difference in height. But the...
Back
Top