Exam III Practice Problems (liquids and pressures)

Click For Summary

Homework Help Overview

The discussion revolves around practice problems related to liquids and pressures, specifically focusing on concepts such as buoyancy, tension in fluids, and the application of Bernoulli's equation. Participants are preparing for an upcoming exam and are seeking clarification on various physics problems.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the forces acting on a block submerged in a fluid, including tension, buoyancy, and weight. Questions arise about the application of the Bernoulli equation and the relevance of free body diagrams. Some participants express confusion over terminology and the use of equations related to fluid dynamics.

Discussion Status

There is an ongoing exchange of ideas with some participants providing guidance on identifying forces and applying principles like Archimedes' principle. Others are exploring different interpretations of the problems and questioning their understanding of the concepts involved.

Contextual Notes

Participants mention constraints such as the lack of a textbook and reliance on trial and error due to limited resources. There are also references to specific practice questions from an online resource, indicating that the discussion is grounded in specific exam preparation.

  • #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
 
Last edited by a moderator:
Physics news on Phys.org
  • #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.
 
Last edited by a moderator:
  • #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?
 
Last edited by a moderator:
  • #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?)
 
Last edited by a moderator:
  • #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
 

Similar threads

Replies
53
Views
6K
  • · Replies 112 ·
4
Replies
112
Views
11K
  • · Replies 66 ·
3
Replies
66
Views
7K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 34 ·
2
Replies
34
Views
5K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 18 ·
Replies
18
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K