Exam III Practice Problems (liquids and pressures)

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SUMMARY

The forum discussion revolves around solving physics problems related to liquids and pressures, specifically using the Bernoulli equation and concepts of buoyancy. Participants clarify the forces acting on a block submerged in water, including tension, weight, and buoyant force, while referencing Archimedes' principle. The discussion emphasizes the importance of understanding free body diagrams and conservation of energy in solving these problems. Key equations and principles, such as the relationship between buoyant force and displaced fluid weight, are highlighted as essential for accurate problem-solving.

PREREQUISITES
  • Understanding of Bernoulli's equation and its applications in fluid dynamics.
  • Knowledge of Archimedes' principle regarding buoyancy and displaced fluid.
  • Ability to draw and interpret free body diagrams for analyzing forces.
  • Familiarity with conservation of energy principles in physics.
NEXT STEPS
  • Study the application of Bernoulli's equation in various fluid dynamics scenarios.
  • Explore detailed examples of buoyancy calculations using Archimedes' principle.
  • Practice drawing and analyzing free body diagrams for complex systems.
  • Review conservation of energy problems, focusing on potential and kinetic energy transformations.
USEFUL FOR

Students preparing for physics exams, particularly those focusing on fluid mechanics, as well as educators seeking to reinforce concepts of buoyancy and energy conservation in their teaching materials.

  • #91
http://online.physics.uiuc.edu/cgi/courses/shell/phys101/spring06/prep2a.pl?practice/exam3/sp99 19, absolutely makes no sense. The steel marble will take room in the cup right? thus making the intial level higher unless the water overflows but they never stated that
 
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  • #92
Alt+F4 said:
http://online.physics.uiuc.edu/cgi/courses/shell/phys101/spring06/prep2a.pl?practice/exam3/fa02 14. So i just said K = 2, W = 2 M = 2 and found an imaginary Etotal.

then i found the kinetic energy of .01 and when i divide Etot / 4 i get the kinetic energy that my equation gave. What am i doing wrong
How did you find the KE at 0.01m? Hint: Consider the change in potential energy as the position changes, then use that to find the KE.
 
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  • #93
Alt+F4 said:
http://online.physics.uiuc.edu/cgi/courses/shell/phys101/spring06/prep2a.pl?practice/exam3/sp01 Question 18

what i did was

pgy = .5p v^2

(1000)(9.8)(.03) = .5(1000)(V^2)

V = .77


Ans: .75

So why am i off by .2



last question. Any hints?
 
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  • #94
Alt+F4 said:
http://online.physics.uiuc.edu/cgi/courses/shell/phys101/spring06/prep2a.pl?practice/exam3/sp99 19, absolutely makes no sense. The steel marble will take room in the cup right? thus making the intial level higher unless the water overflows but they never stated that
Sure the marble takes up room in the cup, but which raises the water level more: having the marble imbedded in the ice, or having the marble tossed in the water? (Hint: Which situation displaces more water?)
 
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  • #95
Alt+F4 said:
last question. Any hints?
You are only off by 0.02 m/s. Your method looks OK to me.
 
  • #96
Doc Al said:
Sure the marble takes up room in the cup, but which raises the water level more: having the marble imbedded in the ice, or having the marble tossed in the water? (Hint: Which situation displaces more water?)
okay so question 18, i understand that it will be the same as inital level, but then 19 there is an object in there that will take room so it will push the water up. I still don't see why the water would be lower? What happened to the water that was at the intial level?

Okay maybe this will clear it, when there saying slightly, how slight are we talking about?
 
  • #97
Alt+F4 said:
okay so question 18, i understand that it will be the same as inital level,
Why is that? What determines the volume of displaced fluid?

but then 19 there is an object in there that will take room so it will push the water up.
It's not just the fact that "it takes room" that's the key. How about this: Imagine a bathtub of water and a big toy boat floating in it. If I take a bowling ball, which will raise the water level in the bathtub more: (1) dropping the ball in the water, or (2) putting the ball on the boat so that the whole thing floats?

The key is: How much water is displaced?
 
  • #98
Thanks everyone for your help, I just aced another exam. I'll be back in a week for finals
 

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