Homework Help

Consider the following: Two objects rest on a wooden plank. One object is twice as heavy as the other. The heavier object is designated "H" while the lighter object is designated "L." A rope is attached to the center of the plank. A crane hoists the rope. Obviously, the plank will tilt. Which object will begin to slide first? The answer, which I found via the static friction coefficent formula (below), is that both objects will begin to slide at the same time. However, why is this the case? Doesn't inertia (the tendancy of objects to resist changes in motion) play into this scenario? While mass does not have an effect on friction, it certainly …

I was going through my engineering book and came across this free body diagram of a structural member. What I don't get is that how did they come up with the 6200N reaction force at the ends of the whole structure? Any help in understanding this would be great. Oh and sorry for the blurry image. My phone is not that great at taking pictures at night =(

I'm doing an online chemistry course and we were directed to do a lab involving cleaning pennies. Basically it involves placing dull pennies in a solution of vinegar and salt to clean the pennies. I know the pennies become dull due to the copper becoming oxidized from reacting with the acetic acid. I've done a bit of searching online as to why we add salt to the solution. I've seen comments that the chlorine in the salt mixed with the hydrogen in the acetic acid to make some HCl, however I've seen many comments saying this is untrue, but I've seen no alternatives as to the function of the salt. My only guess is that the salt speeds up the reaction because of its a…

Why do some elements have 1 electron on the outer shell while there can be more electrons in the previous shell? For example, all the alkali metals.

I am faced with the question: The vapor pressure of pure ethanol at 60 °C is 0.459 atm. Raoult's Law predicts that a solution prepared by dissolving 10.0 mmol naphthalene (nonvolatile) in 90.0 mmol ethanol will have a vapor pressure of __________ atm. If I convert the milimolar to molar I get: 0.01 mol Nap. 0.09 mol Eth. and 0.10 mol total Thus the mole fractions should be: X_Nap. = 0.01 / 0.10 = 0.10 X_ Eth. = 0.09 / 0.10 = 0.90 Which according to Raoult's Law Vapor Pressure of Soln. = Sum of Vapor Partial pressures 0.459 atm * X_Nap. -{0.10} or 0.459 * 0.10 = 0.0459 Partial Pressure Nap. 0.459 atm * X_Eth. -{0.90} or 0.459…

i help to find the bond type of polyatomic ions but first i need to find the difference in electronegativity of them. I have no clue how to do this. ammonium sulfate (NH4)2SO4 magnesium phosphate Mg3(PO4) There are more but i want to know how to do those first. can anybody help me... i need to know how to do this this doesnt help me at all... whatever

I have a chamistry final tomorrow and was trying to study. I my professor's notes, I found an altered form of the ideal gas equation PV=nRT. It's been quite a while since I've had a good math course, so I'm wondering if someone here can show me how PV=nRT is rearranged to give n/v = P/RT I'm having this problem because I don't remember some basic math tricks. Been a while. I'd like to understand how this equation is derived. Thanks in advance for the help.

Hey guys, this is my last homework assignment of the semester and it's on counting. I'm having a little trouble doing it. 1) A bridge hand consists of 13 cards from a standard 52 card deck. How many bridge hands contain cards from exactly two suits? I said step 1) pick suits (4 over 2) as in pick 2 suits from 4 suits step 2)pick cards (26 over 13) as in pick 13 cards from the 26 cards of the two suits you picked in step 1. Answer: (4 over 2)*(26 over 13) This one I feel pretty good about. 2)A club has 25 members: 10 men and 15 women. In how many ways can a committee of 5 be formed. Answer: (25 over 5) as in of all 25 people pick 5 f…

Hello, I have an assigment and need your help.. please help me , Noor,

I have a question on membrane fusion. http://tinypic.com/view.php?pic=fao4nk&s=6 During cell-cell fusion, proximity and localized membrane disruption are key events. Look at the accompanying picture and describe the flow of transport that must have occurred to allow formation of the final cell from the original cells and vesicles. For every fusion event, you must identify the proteins involved in trafficking and use them correctly. HINT: Remember that fusion events will MAKE new sections in the target cell or vesicle So, i know membrane-membrane recognition, proximity,Disruption of bilyar, i.e hemifusion, fully bilayer fusion are all requirements for f…

Ok we're doing diels-alder reactions and I have this reaction I'm not sure if there is no reaction or if i do have the correct answer here. 1,3-butadiene + trans-1,2-N=_CCH=CHC=_N =_ are triple bonds. I came up with a Hexene that has 2 CH2N groups on the 3,4 carbons that are trans to eachother and of course the double bond at the 1 carbon. I came up with the correct soultion right or was it no reaction for some reason that I can't see?

HI, please help me..i comsume a lot of time to think this but i still cant slove it~~~~ Consider a combinational logic circuit with three inputs a,b and c, and six outputs u,v,w,x,y,and z.The input is an unsigned number between 0and 7,and the output is the sequare of the input.The most significant bit of the input is a,and the most significant bit of the output is u.Create a truth table for the six function.

I've a few homework questions involving multiple integrals. I think most of my problems come from the limits of the integrals. Pointers would be most welcome. This is the 1st one. [math]\int \int_D2xydxdy[/math] where D is the bounded region between [math]y=\frac{1}{2}x^2[/math], [math]x+y=4[/math] and the [math]x[/math]-axis. Wasn't sure whether to split the integral or change the order if integration here (but both should work, right?), so i tried both and got very different answers. So changing the order of integration i make the limits: [math]\int_2^{-4} \int_{4-x}^{\frac{1}{2}x^2}2xydydx[/math] For which eventually i get 2752 - seems too big. Sp…

I have this assignment asking us to find the polyhedron described by the equation |x|+|y|+|z|=1. The question also asked us to justify the answer. After some calculation, I got the result that the polyhedron is a cube. I have the feeling that I am wrong with the answer as the top student in our class has a different answer. Below are my attempt to solve the question: From http://en.wikipedia.org/wiki/Octant_(solid_geometry), I got 8 different plane equations: x+y+z=1 -x+y+z=1 -x-y+z=1 -x-y-z=1 x-y+z=1 x+y-z=1 x-y-z=1 -x+y-z=1 So, with the knowledge of plane algebra, the normal for each plane is: (1,1,1) (-1,1,1) (-1,-1,1) (-1,-1,-1) (1,-1,1) (1,1,-1) (1,-…

Question: Which of the following types of functional groups react with Grignard reagents: alkenes; terminal alkynes; non-terminal alkynes; alcohols; alkanes; tertiary amines; secondary amines? I know that grignard reagents are strong bases and nucleophiles, and so they will react with alcohols, terminal alkynes, and secondary amines definitely. Alkenes, alkanes, and non-terminal alkynes will not react, right? The one I'm not sure about is the tertiary amine...I have not seen an example of a grignard reagent reacting with one but I don't see why not...too crowded, charge distribution, I'm not sure?? Is my thinking correct on this?? Thanks!

Hi, First of all i want to say sorry if my language is not good enough to explain because English is not my mother language And sorry if I post this in a wrong sub-forum So I have an assignment from my college about Physics, specifically Fluids In a team of about 7-8 people We have to make a mini air balloon based on Archimedes principle.. And the minimum requirements are : 1.) Able to fly 0,5 meter above its initial position 2.) Fly about 1 minute 3.) Max Mass of the source of heat : 20 gram The questions are : 1.) What material that if burnt or act as a heat source could produce great energy in a minimum mass ? So the thing that is commonly used is …

I have a MS, IR, NMR problem and I don't know where to go from here. I have everything that I know for sure written on the doc and I'm pretty much stuck trying to figure out this structure. I've never done any NMR, IR, or MS before so this is pretty confusing right now. Any direction on the C13 spectral data would be fantastic and does what I have written so far seem correct? So far the closest thing I've got to the answer is a tert-butyl group attached to a carbon with a double bond O an OH coming off of it. This comes out to the relative formula mass of 102 but there's only 2 types of H where as the H NMR says there should be different kinds of H.

Ok the question goes the diels-alder mechanism is best described as a. proceeding stepwise by cation intermediate b. proceeding stepwise by radical intermediate c. proceeding by a syn cycloaddition d. proceeding by an anionic radical cycloaddition e. Proceeding by a "no mechanism" electrophilic addition I know that a and b are incorrect because if it was stepwise then the stereochemistry would not be retained the reaction wouldn't work out. I'm leanin toward E as the answer but I'm not positive.

I've already submitted this question to yahoo answers, but didn't get the answer i was looking for. The question was, "When something sublimates, does it actually skip the liquid state?" Most of the answers were something like, "No, sublimation means it skips the liquid state." I already know this from 8th grade chemistry, but it still doesn't make sense to me. So I'm going to rephrase the question for those willing to answer my question When a solid melts, the spaces between the particles widen and turns into a liquid, right? And when a liquid evaporates, the space between the particles widens even more and turns into a gas, right? Sorry I;m stating the obvious and n…

Hello! I'm a 4th year high school student. Our physics teacher required us to do a Science Investigative Research. The topic of our research was "Magnetic Fan". It's quite simple. We will use the movement caused by magnets to rotate the blade of a mechanical fan. But we have a problem. IT DOESN'T WORK! We used this design: We were hoping to get some help from the forum. Remember: the fan blade should rotate AND magnets should have a significant part in rotating it. Thanks in advance to anyone who will help us!

Hi Everyone, i have this assignment due in 2 weeks its on recreating a Model in class of the Michelson-Morley experiment to detect the aether. My first problem after a lot of research on youtube clips and just general study is, why? I understand that they were trying to prove that light needs a medium to travel therefore they were trying to discovder the actual medium it does. I did go to my teacher and asked her and she said a way to Model the experiement would be to hang a pendulum off a string have a fan blowing against it and release the pendulum each time, however im struggling to see what relevance that has with the experiment. So Could someone please tell m…

Q : In a group of 50 persons,14 drink tea but not coffee and 30 drink tea. Find: (i) how many drink tea and coffee both; (ii) how many drink coffee but not tea. i think the answer to (i) is n(T intersection C) = 30 -14 = 16 what is the answer to (ii) ? i cannot solve the question - either (a) i'm an idiot! or (b) i don't understand the question [ i don't know whether (b) necessarily imply (a) even when English is not my mother tongue] © ( this option is avoided for obvious reasons! ) so somebody plzzzzzzzzzzz help!!!!!!!!!!!!!!!!!!!!!1

Hello , I prepare my thesis whose subject is: simulation of vortex tube performance. I use a group of equations that have been referred on the thesis :''QUANTITATIVE OBSERVATIONS ON MULTIPLE FLOW STRUCTURES INSIDE RANQUE HILSCH VORTEX TUBE'', but i met some problems in the implementetion of them. Has anybody any idea about the coefficients of friction that are used in this thesis in the last pages? Thank you in advance.

Dear all, I am new to this forum and very happy to find such a community to chat with and to start with, ask for help! (I hope I'm in the right section) I was wondering if its possbile someone can help me download a book about electrophoresis from Wiley library called : Mechanisms of protein silver staining in polyacrylamide gels: A 10-year synthesis. Dr. Thierry Rabilloud*. ELECTROPHORESIS, Volume 11, Issue 10, pages 785–794, 1990 If possible, you can send it to my email: mghazaly@minapharm.com Thank you

Hello! I am, in relation to a big assignment in my school, supposed to do a comparative analysis, and two/three rhetorical analysises in relation to the cold war. I am writing about the USA-soviet relations during the period 1980-1990~. Therefore, I am looking for some material to analyze - the goal with the comparative analysis is to show a change in Reagan's opinion on Soviet, through his speech. I have already chosen the "evil empire speech" and I am currently considering "the brandenburg speech". However, I am very interested in getting some ideas for material(speeches) that could be interesting and relevant in my assignment. Cheers mnlaursen