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Physics Question

 
 
JackK
 
Reply Sat 13 Sep, 2014 08:29 pm
Hey guys, here is an interesting physics problem I found in a textbook. How would you guys solve it?

Here is the picture that goes with the problem:
http://pbrd.co/1m4FPzc

The problem:
A sealed cauldron with water inside is heated by fire and steam is generated. The steam causes the cauldron to spin at high rates. The steam escapes through two spouts as shown in the diagram. The container has a radius of 0.20 m and a mass of 10 kg. The 2 spouts have an insignificant mass, but they extend 0.10 m above the surface of the container. The cauldron is hollow. Disregard the moment of inertia of the steam inside.

The questions:
What is the moment of inertia of the container?
If the pressure inside reaches 1.5 atm, what is the angular accel? (Area of spouts to be circles w/ radius 0.010 m.)
How much energy is inside the container?
If the energy was converted to rotational kinetic energy, what would be the angular velocity?
Explain the full energy cycle of the cauldron (start at where energy originates, explain transformations of energy, and explain what happens after the fire is put out.)
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Type: Question • Score: 1 • Views: 594 • Replies: 11
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One Eyed Mind
 
  1  
Reply Sat 13 Sep, 2014 08:33 pm
And this is why modern science had failed Nikola Tesla.

Life is to be simplified; not complicated.
JackK
 
  1  
Reply Sat 13 Sep, 2014 09:08 pm
@One Eyed Mind,
Lol yep. But I still want to know how to solve it. Giancoli doesn't give any explanation on it whatsoever.
One Eyed Mind
 
  1  
Reply Sat 13 Sep, 2014 09:11 pm
@JackK,
I assure you, I would like to help, but numbers and names never have been my strong suite - my brain destroys labels and it "feels" the imagination I have; it cannot "see" the imagination. So shapes, color, distinctions, patterns, vibrations, is what I feel.

Gladly, I have contributed in some way. Just not in the way you intended.
JackK
 
  1  
Reply Sat 13 Sep, 2014 09:20 pm
@One Eyed Mind,
aah thats true. Do you know anyone who could help out in this area?
roger
 
  1  
Reply Sat 13 Sep, 2014 09:26 pm
@JackK,
I know one or two that could help - if they happen to see the post.
One Eyed Mind
 
  1  
Reply Sat 13 Sep, 2014 09:26 pm
@JackK,
From what I have seen, if you see someone by the name "Engineer" come in, you are in good hands.
JackK
 
  1  
Reply Sun 14 Sep, 2014 12:41 am
@roger,
thanks
0 Replies
 
JackK
 
  1  
Reply Sun 14 Sep, 2014 12:41 am
@One Eyed Mind,
ok ill look out for him
0 Replies
 
engineer
 
  1  
Reply Mon 15 Sep, 2014 01:17 pm
@JackK,
I'm not going to promise all of this is correct, but this is my take.

Quote:
What is the moment of inertia of the container?

The moment of inertia of a hollow sphere is 2/3 mr^2 = 0.267 kg m^2.

Quote:
How much energy is inside the container?

Let's assume it is an ideal gas. The energy content = cv nRT where cv is the dimensionless heat capacity ~ 2.5 for water. nRT = PV from the ideal gas law. P=1.5 and V = 4/3 pi r^3 = .0335 m^3. One atm.m^3 = 101,325 joules. That makes the energy (2.5)(1.5)(.0335)(101325) = 12.7 kJ.

Quote:
If the energy was converted to rotational kinetic energy, what would be the angular velocity?

Energy = 1/2 I w^2
12.7 kJ = .5 ( 0.267 kg m^2) w^2
w = 975 radians/sec
0 Replies
 
contrex
 
  1  
Reply Mon 15 Sep, 2014 01:28 pm
@One Eyed Mind,
One Eyed Mind wrote:
Gladly, I have contributed in some way. Just not in the way you intended.

You have contributed nothing.
One Eyed Mind
 
  1  
Reply Mon 15 Sep, 2014 06:03 pm
@contrex,
According to your very small scope, of course.

Expand and maybe you'll see.
0 Replies
 
 

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