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Homework Help

For assistance with (but not answers to) homework problems.

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A simple reminder to all: this is the "Homework Help" forum, not the "Homework Answers" forum. We will not do your work for you, only point you in the right direction. Posts that do give the answers may be removed.

  1. Started by richard13,

    Hi there. Got a problem. I have the equation P equals rho x omega x upsilon x s Problem is that I do not know what each of the symbols correspond to and what units I need to put them in as. Can anyone help or point me in the right direction. I have been looking for the answer for this one for ages. Its possibly shown in a different way elsewhere? Many Thanks Rich

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  2. Started by richard13,

    Hi, wonder if anyon could help? I am looking to find the displacement amplitude of a speaker. I have the diameter of the speaker, the frequency, air pressure and density and asumed speed of sound. Anyone point me in the right direction for an equation to fit this? THanks Richard

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  3. Started by Fortissimo,

    Guys I'm doing an introduction to statistics course and I'm sort of stumped. I can manage the calculation aspect as its more straight forward but when u have to prove stuff, I'm hopeless. Any help with this please, Prove that if event A and event B are not mutually exclusive, then P(A or B) = P(AUB) = P(A) + P(B) - P(AnB) Would appreciate any help. Thanks.

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  4. Started by Baykko,

    The covalent radius of an aluminum atom is 1.18 x 10^-8 cm. Assuming that in aluminum foil,the atoms are packed one on top of each other, how many atoms thick is a sheet of aluminum foil? (if aluminum thickness= 0.0017) for this.. ive tried dividing the thickness with the radius/diameter, giving me answer of around 14k and 7k but not sure if that is correct or what is the right way to solve it. then i have no idea what to do for this problem, A cube of aluminum of side 2.00cm has a mass of 21.60g. Using the covalent radius of an aluminum atom, calculate the volume of the "empty space" inside the cube.

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  5. how many times can we differentiate this splitted function on point x=0 ?? [math] f(x) = \{ x^{2n} \sin (\frac{1}{x}) ,x \ne 0 [/math] on {0,x=0}

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  6. Started by Mb94,

    Hi. I just started year 10 and we already have an assignment. This year I need to do well in Science to get into physics, so I figured I should get all the help i can for my assignments. We have to write a 300+ word essay ("response") to this statement: "Hydrogen and bio-fuels are the only transport fuels that even putatively tackle both global worming and oil depletion, and they appear to be completely inadequate to the task" The Main question is: Do you think that hydrogen and biofuels are the only fuels available to ward off the consequences of running out of oil and climate change? Your discussion should include an analysis of the hydrogen and biofuels indus…

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  7. Started by gd,

    may i know the full answer for this....it was posted earlier by candiishop bt i cant see the full answer...here is the question : Predict what would happen to erythrocytes placed in a solution containing 300mOsm/L urea and 300mOsm/L sucrose (i.e. a total of 600mOsm/L of particles in one solution; and remember that this is NOT made by mixing equal volumes of 300mOsm/L urea and 300mOsm/L sucrose). Fully explain your answer.

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  8. Started by jesusfreak0428,

    Ok I don't know if I'm gonna sound dumb, but I am doing my 6th grade science experiement and i need to know what the control is. I am going to test tap, bottled, fountain, and toilet water. I want to see which one has more bacteria and which is more drinkable, i read somewhere that toilet water is just about the same as fountain i want to know. Can somoen tell me what the control is because i cant figure it out

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  9. Started by Tracker,

    This is a question I have worked on in Stats and my answer does not line up with the solution manuals. [math] P(A' \cap B' \cap C) = P© - P(A \cap C) - P(B \cap C) + P(A \cap B \cap C) [/math] My answer there is a negative before [math] P(A \cap B \cap C) [/math]

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  10. Hey, just wondered if you guys could clear something up for me:D When using the beer lambert law, should you use the Absorbance value at Lambda max, ie the highest absorbance? (because presumably using different values would lead to different molar absorption coefficients, which isn't good)

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  11. Started by blazinfury,

    Suppose two quantities, A and B, have diff dimentions. Determine which of the following arithmetic operations could be physically meaningful (select all that apply). 1. AB 2. A/B 3. B-B 4. A-B 5. A+B I have tried choices 123 and 13, yet both were wrong. I know that 4 and 5 are wrong because you are subtracting different units. I thought that 2 was wrong because what if B=0, then it would be undefined. For 3, you are subtracting within the same unit, so it has to be correct. I am not sure at this point. Any advice is welcome.

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  12. Started by transgalactic,

    i am given two differentiable function f and g . prove that for u(x)=max(f(x),g(x)) and v(x)=min(f(x),g(x)) there is one sided derivatives ??

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  13. Started by glo1000,

    First off, I am sorry for being blunt with my questions but I am honestly stumped. Can anyone lend a thought? The first question I have no idea how to even get started. Estimate the copy number of pET22b+ in the average E.coli cell. You may assume that there are approximately 1 X 109 E.coli cells in each mL of overnight-saturated culture. The size of the pET22b+ plasmid is ~5500 bases, the size of the insert is ~500-800 bases, and the average molecular weight of a nucleotide base pair is 660 g/mol. Or this question: How could you use this sequence to design a 5’ primer that could sequence your own DNA to determine if you have any genetic polymorphisms in yo…

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  14. Started by carl1,

    Compound B is acetylcholine, a neurotransmitter found in the human body. It binds to receptors, leading to nerve stimulation. COMPOUND B CH3 O | || H3C- N+- CH2- CH2- O-C- CH3 | CH3 (in case the thread does not show correctly, the CH3 with the single line underneath places above the N+, the O with the two || below it places above the C and the CH3 with the line above it places below the N+) (i) Name two types of interaction, other than van der Waals or hydrophobic interactions, by which compound B could bind to the receptors. (ii) Identify two different types of g…

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  15. Started by aaronaldo,

    I need to work out a perctange yield for my experiment, however i am having trouble balancing the equation. H2SO4 + C6H5Br + HNO3 --------------> C6H4BrNO2 + H2O this is what i have so far.. but there is no S on the right side of the equation.... im very confused.

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  16. Started by transgalactic,

    http://img265.imageshack.us/img265/5461/63848612xp9.gif

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  17. I am trying to prove the follow two questions without using the differentiation formulas for inverse trig. or inverse hyperbolic functions. [math] \arcsin(u) = \arctan(\frac{u}{\sqrt{1 - u^2}}) [/math] I have been looking at it as [math] \frac{opp}{adj} = \frac{opp}{hyp} [/math] but something in my steps is off. I am also trying to solve [math] \frac{d}{dx}[\tan(\arcsin(x))] = \frac{1}{(1 - x^2)^\frac{3}{2}} [/math]

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  18. Started by Ryan23,

    How do you make 200ml of a 0.1M solution of a substance that has a molecular weight of 121.1g/mol?

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  19. Started by transgalactic,

    here is the question and how i tried to solve it??

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  20. Started by yo_wazzup41,

    Find the lattice enthalpy of MgF2(s) Mg(s) + F2(g) -------- MgF2(s) -1102 kJmol-1 1/2F2(g) -------- F (g) + 79 kJmol-1 F(g) + e- -------- F-(g) -348 kJmol-1 Mg (s) -------- Mg(g) +150 kJmol-1 Mg (s) -------- Mg^2+ (g) + 2e- +2186 kJmol-1 My calculation is : -1102 + 79*2 + 348 *2 - 150 -2186 and my answer is :- 2584 but the modal answer is -2821 can anyone please help me thankx

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  21. Hi, hopefully someone can help me with this question: 1. Write an equation to show the reaction between ethanol, C2H5OH and methyllithium, CH3Li. In this reaction, ethanol is a Lewis acid and CH3Li is a Lewis base. Draw all non-bonding electrons and show electron flow with curved arrows. I basically can't figure out the equation: should it produce CH4 and C2H5OLi or LiOH and C5H8? Also then, I need help with the electron flow. Thanks in advance, K.

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  22. Started by yo_wazzup41,

    acid is used as a catalyst for the reaction between propanone and iodine. what is the purpose of adding sodium hydrogencarbonate too in the reaction? im doing a report and i dont know how to answer this question can anyone help me thanks

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  23. Started by Ugouka,

    Well, in my Honors Physics class, we just did a project with little hotwheels cars and rocket engines. Out objective was...well...to make them go as fast as possible. Our teacher basically gave us power tools and rocket engines to play with..because that couldn't go wrong or anything:rolleyes:. Anyway, I'm just curious if you guys have any suggestions on how to improve the design we used for our group. Our track had to be 5 meters long and we used photogates to record our time. The gates were spread out 1 meter apart to give us the average speed. What my group did was this: We took 5 meters of 2X4 wood and attached a wall to both ends of the track. At the start s…

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