# Search results for query: *

• Users: Qube
• Order by date
1. ### Normal Stress in Rods Experiencing Temperature Changes

Now here is the part where I'm sort of stumped myself: Could someone let me know if my reasoning is valid? The professor explained it during office hours and all I got out of that was that something cancels out and the answer is 0.
2. ### Proper free-body diagram for a shaft experiencing multiple torques

I don't see a direct constraint on Tmax in this problem that is given. I'm still unclear on what you mean by: The only constraint I see is on torsional shear, which is a function of Tmax.
3. ### Proper free-body diagram for a shaft experiencing multiple torques

1500-T<Tmax I'm still unclear on what you mean, sorry.
4. ### Proper free-body diagram for a shaft experiencing multiple torques

I don't understand, but I'll give it a try. Are you saying to plug 900-T, 1500-T, and 1800-T into the equation, shear=Tc/J and try to maximize the value of T?
5. ### Proper free-body diagram for a shaft experiencing multiple torques

Okay, scratch all that. I managed to figure it out by finding similar problems. Thank you for the guidance. I hope that this post of mine is error-free! We need to start by applying the right-hand rule to the applied torques, with the sign convention that a torque directed away from point E is...
6. ### Proper free-body diagram for a shaft experiencing multiple torques

Okay, I reworked the problem. I drew a torque diagram. It seems that the maximum possible value of the unknown torque, T1, is 327 Nm. From there, it seems that the internal shear stress in section CD is about 47 MPa, and the internal torque in DE causes the bar to hit its shear stress limit...
7. ### Proper free-body diagram for a shaft experiencing multiple torques

Thanks! You are right, it is J=pi*c^4/2. I will rework this problem and see if I get the right answer this time...
8. ### Proper free-body diagram for a shaft experiencing multiple torques

I wish to draw a proper free-body diagram for this shaft. However, my FBD does not agree with the solutions manual. If someone could point out where I erred, that would be great. This is what I drew: From my FBD, it is clear that the maximum torque is present in section DE of the shaft. We...
9. ### Finding the maximum height of a projectile

Can we alternatively use energy methods to solve for the height of the water?
10. ### Finding the maximum height of a projectile

I got a non-response response, so I guess I'll just chalk this up to YET another case of bottom-barrel textbook editors doing bottom-barrel work in writing questions and solutions. Book in question is Hibbeler's Dynamics, 14th edition. I used Hibbeler's Statics text last semester, and the...
11. ### Finding the maximum height of a projectile

It seems that to solve the problem as stated would actually involve finding an equation relating the angle, theta, and the height on the wall, h. And then you would take the partial derivative of height equation with respect to theta to find the extrema. I'm currently awaiting a response :).
12. ### Finding the maximum height of a projectile

That's a great question, and from my discussions and research, I was told that this assumption is incorrect in this problem. That being said, the book's solution manual makes that assumption, and so does my Dynamics professor: But it seems that even if we take this assumption as valid (which...
13. ### Finding the maximum height of a projectile

Using the equations for constant acceleration, we can write the following set of equations for this problem: We have the following known physical constraints: Solving the above system of equations and constraints with a computer algebra system: So, all the solutions I found make...
14. ### Finding the final y-position of a projectile

Thanks, so what's the takeaway here for finding the final position of a particle that lands on a hill? We have the book, which asks for "(x,-y)," and the book comes up with the "-y" displacement equation. We have a famous professor on YouTube solving for "(x,y)" and he comes up with the same...
15. ### Finding the final y-position of a projectile

Here's a much more condensed version of what I'm asking: who's correct, the book or the teacher's method? The points of impact are are in x and y. Time is "t."
16. ### Finding the final y-position of a projectile

Summary:: After firing a projectile from the top of a hill, where does it land on the hill? I disagree with the professor in approach and final result. Problem Statement: Relevant Formulas: Attempt to Solve: I'm very familiar with these types of problems. I'm not here for help solving...
17. ### Engineering Should one include friction in this free-body diagram?

Problem statement: Attempt at a solution: 1) There are no relevant moments that need to be drawn in this free-body diagram. 2) There is tension in the chain DE that is pointed away from the truck, i.e. from D to E. 3) There are "ground" reaction forces at points A and B pointed up toward...
18. ### Converting source intensity to the maximum reach of beam flux

We can solve for the maximum 5 lux illumination distance with the above equation. E = 10.76*(35,000/d^2) d = 275 feet (approximately). However, the 5 lux illumination distance is not 275 feet. The 35,000 cd value is not an axial intensity value. It is at a point that is slightly down and to...

B
20. ### Electropositivity - 2nd opinion needed

Homework Statement I have a significant problem with the following excerpt from a general chemistry text: Note that ON stands for oxidation number (state). The excerpt is with regard to polyatomic anions - specifically, chloride ion and its related polyatomic anions. >It now follows that as...
21. ### Diels-Alder - Explanation?

Yes I'm sure he didn't mention orbitals at all.
22. ### Diels-Alder - Explanation?

Homework Statement This is my prof's explanation of Diels-Alder ... below is the mechanism and some resonance structures he drew to explain the concerted movement of electrons to the class ... Homework Equations Nucleophiles attack electrophiles. Electrons in HOMOs go into LUMOs. The...
23. ### Stability of Sulfides

Homework Statement The attempt at a solution 1) Is the above excerpt describing pi-backbonding? It seems to be describing some form of backbonding because the electron density is moving away from the positively charged metal cation (rather unexpected based on superficial Columbic analysis)...
24. ### Mechanism of saponification

Well, I didn't want to go through the entire mechanism from start to finish since the beginning isn't relevant. It all begins the same way - nucleophilic attack at the carbonyl carbon.
25. ### Mechanism of saponification

Questions: 1) How's my reasoning? 2) Who's right in reality?
26. ### Mechanism of saponification

Homework Statement Problem: I am told that the first mechanism is operative in saponification. The Attempt at a Solution However, this strikes me as wrong because the first mechanism involves the formation of dianion. Using hydroxide ion to abstract a proton and make that particular...
27. ### Steric Effects on Basicity

Yep, I realized that solvation is a factor. I mentioned this to my professor and although he did not outright disagree with me about solvation, he dismissed it as being basically too advanced for the students. I could definitely see sterics having an effect on solvation of the conjugate base...
28. ### Steric Effects on Basicity

Homework Statement How do sterics affect basicity? Homework Equations Sterics has to do with kinetics. Basicity is a thermodynamic property. Nucleophilicity is a kinetic property. The Attempt at a Solution So is the answer "sterics don't affect basicity"? I can't see why sterics...
29. ### PH dependence of reduction of oxygen

Isn't the activity of the proton higher in acidic solution than in basic solution?
30. ### PH dependence of reduction of oxygen

So if I'm understanding you correctly the reduction of H+ in water solution to hydrogen gas is dependent on the availability of protons. It is easier to take a positive charge from a positively charged molecule rather than a positive charge from a neutral molecule, so the reduction of H+ in...
31. ### PH dependence of reduction of oxygen

Gotcha. Does this have to do with the Ka values of hydronium ion and water?
32. ### PH dependence of reduction of oxygen

Why much easier? Isn't it the same HO bond?
33. ### PH dependence of reduction of oxygen

Why not just take protons from water then? There are 50 plus moles of water even in most acidic solutions ... Excluding things like 18 M sulfuric acid.
34. ### PH dependence of reduction of oxygen

Cool. So why does the potential decrease relative to the standard hydrogen electrode as the pH goes up for the oxidation of hydrogen protons? I'm guessing that it's easier taking hydrogen from hydronium ion in acidic solution than it is taking hydrogen from water in basic solution, since...
35. ### PH dependence of reduction of oxygen

Sweet. Regarding the Nernst equation and how it predicts potential to decrease with increases in pH: Is the protonation of oxygen dependent on kinetic or thermodynamic factors? I'm guessing thermodynamic factors because in more basic medium, the thermodynamic potential for protonation...

Anyone
37. ### PH dependence of reduction of oxygen

Homework Statement Why is this true? Why is it that the reduction of oxygen is more favored in acidic solution rather than in basic solution? Homework Equations Acids are proton donors. The Attempt at a Solution Does this have anything to do with the fact that the...
38. ### Polarity of the Binary Halogen Acids

Does the polarity of the binary halogen acids increase or decrease down the group? I have one argument for decrease based solely on electronegativity considerations. I have one argument for increase based on orbital overlap and electron density. Taking electron density in an orbital to be...
39. ### Naming of Haloalkane (Disputed)

Thank you for the thorough response. It seems that our textbooks greatly simplify naming considerations to picking out the longest chain. My teacher also changed the answer to 4-(1-chloroethyl)-4-methylheptane. Oh well.
40. ### Naming of Haloalkane (Disputed)

My teacher insists the name of this compound is (2S)-chloro-3-methyl-3-propylhexane Shouldn't it be 4-(1-chloroethyl)-4-methylheptane? (Ignore R,S configuration for now). Chemoffice also tells me 4-(1-chloroethyl)-4-methylheptane. I think it's the latter because I've consulted three...
41. ### Does the Textbook Answer Make Sense? 3 Carbons

Which textbook is this?
42. ### Polar or nonpolar?

Molecules can have dipoles and yet be non-polar. For example, carbon dioxide has two permanent dipoles yet it is non-polar.
43. ### Most Exothermic Combustion of Hydrocarbon

You're right! I missed that the cis isomer had both methyls in equatorial positions; I don't know how I overlooked that. Thanks!
44. ### Most Exothermic Combustion of Hydrocarbon

Flipping the chair of course changes how the ring is numbered and the axial/equatorial configurations. I hope you know what you're talking about.
45. ### What is the difference between acid,base,salt, amphoteric and neutral?

These terms can be found in any chemistry textbook or the IUPAC Gold Book, which is available readily online.
46. ### Nomenclature - IUPAC and Common Names

Homework Statement What if we stuck with the IUPAC name and called the isopropyl group a 1-methylethyl group? That would definitely reverse the alphabetical priorities; because the substituents here on the hydrocarbon are on equivalent positions, we must give the lower number to the...
47. ### Lewis structure of SO2

http://en.wikipedia.org/wiki/Hypervalent_molecule
48. ### Lewis structure of SO2

Atoms generally don't expand their octets. Unless you're dealing with d-block elements.
49. ### Lewis structure of SO2

It's because the d-orbitals aren't generally accessed by sulfur. The d-orbitals are too high in energy. So sulfur just sticks with structures that are best described using charge-separated Lewis structures.
50. ### Lewis structure of SO2

Perhaps not to the more calculation-inclined chemists!