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  • Users: bard
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  1. B

    Volume help!

    Find the region enclosed by x=3y and x=-y^2+4. Set up integrals both shell and disc that represent the volume when this region is revolved about y=4. i got the shell method, how would i represent the disc method> pi integral(-4,1) (3y-4)^2-(-y^2)^2 --this is wat i got for disc method...
  2. B

    Related rates and sand

    Sand is falling onto a cone-shaped pile at the rate of 9pi cubic feet per minute. the diameter of the base is always 3 times the height of the cone. At what rate is the height of the pile changing when the pile is 12 feet high. work: dV/dt=+9 ft^3/min d=3h then r=3h/2 dr/dt=(3/2)...
  3. B

    Please help check work

    Can someone please check my work, thank you Discuss any discontinuities. classify each discontinuity as removable or nonremovable. (this is a peicewise function) f(x)={sin(x), x<-3(pi)/2 {tan(x/2), -3(pi)/2<x(less than or equal to)0 {(-3x+1)/(x-2), 1<x<3 {-sqrt(x+6), x(greater than or...
  4. B

    Peicewise limit help

    ok so lim(x->1+)=(1+1)=2 lim(x->1-)=(1+1)=2 so the limit exists, i don't understand how that helps in finding the overall limit of F(x) at 1.
  5. B

    Peicewise limit help

    sorry that should be x+1
  6. B

    Peicewise limit help

    F(x)= 2x^2, x<1 3, X=1 X+, x>1 Find lim(x-->1) f(X) f(1)= not exactly sure how to do this. would not f(1) be just 3, since it is defined as that in the function. I am not sure about how to take that limit. Thanks
  7. B

    Limit lim(x->pi/4) tan(2x) =tan(pi/2)

    lim(x->pi/4) tan(2x) =tan(pi/2) wat to do after this, it is undefined
  8. B

    Signalling help

    This seems similar to A. If it connects to the ends then we can liken this phenomenon to the telephone cord ends acting as the synapses. Is this correct?
  9. B

    Signalling help

    I just need someone to please check if my answers are correct. Cells communicate in ways that are analogous to human communication. Decide which of the following forms of human communication are analogous to autocrine, paracine, endocrine , and synaptic signaling. A) a telephone...
  10. B

    Bio Help Please

    INtermediate filaments function as tension-bearing elements to help maintain cell shape and rigidity, and serve to anchor in place several organelles, including the nucleus and desmosomes Ok if this is true then wouldn't a nerve cell in the spinal cord of a mouse need the filaments to...
  11. B

    Bio Help Please

    Which of the following types of cells would you expect to contain a high density of cytoplasmic intermediate filaments? A) Free living amoeba (the answer is no, but why? Is it because the amoeba has to move) B) Human skin epithelial cell C) smooth cell in the digestive tract of a...
  12. B

    Proteins synthesized in a cell

    So then all three instances would have to pass through the rough ER?
  13. B

    Proteins synthesized in a cell

    The ribosomes are what make it look rough I believe
  14. B

    Proteins synthesized in a cell

    Yes I know that it is the rough endoplasmic reticulum that is involved in protein synthesis
  15. B

    Proteins synthesized in a cell

    Actually, for C, it says secreted outisde the cell. Then I believe it would follow the same pathway, Cytoplasm-ER(synthesis of soluble proteins)-Golgi-(the packaging) and then from there sent to other parts of body. And for A, is it that it will stay in the cytoplasm where there are ribosomes...
  16. B

    Proteins synthesized in a cell

    I have been asked to describe the pathway the following types of proteins follow and where they are synthesized in the cell. (a) Soluble proteins meant to remain in cytoplasm- Here wouldn't this follow the pathway cytoplasm-ER-golgi-exocytosis\ (b) membrane proteins meant to remain...
  17. B

    Protein to Protein Interactions

    How do protein to protein interactions and/or protein-nucleic acid interactions underlie the cellular processes of Replication, transcription, and metabloism. Well i know that protein -protein reactions underlie all processes in the cell. For example i think in translation the ribosome is...
  18. B

    Monomer Help Please

    I was hoping for a further explanation of why they save energy by this process. Thank You
  19. B

    Monomer Help Please

    Hi, Why is it better for a cell to synthesize polymers such as proteins carbohydrates by linking together monomers than to synthesize them from scratch> I believe it is because it would take too much energy to link them together from scratch. Since they already have these monomers the...
  20. B

    Importance of conformational changes during catalysis

    Hi everyone, my teacher talked about the importance of conformational changes during catalysis. But I don't understand the importance of the changes. Can someone help me understand?
  21. B

    Calculate delta h of this eq

    calculate delta h of this eq 2N2 + 5o2 -> 2N2O5 giventhis data h2 + 1/2o2 -> h20 and delta h of that is -285.5 n2o5 + h2o -> 2nho3 delta h -76.5 and 1/2n2 + 3/2 o2 + 1/2h2 -> hno3 delta h -170.3
  22. B

    DNA binding proteins

    In general how do DNA-Binding proteins bind to DNA? Many DNA-binding proteins bind to specific sequences of DNA bases. How do the proteins accomplish this sequence recognition. My answer: In general, DNA binding proteins possesses certain structural motifs, such as helixes, which enable...
  23. B

    Antifreeze proteins help

    Anyone know the answer to this ridiculous problem Antarctic notothenioid fish avoid freezing in their perpetually icy environment because of an antifreeze protein that circulates in their blood. This evolutionary adaptation has allowed these fish to rise to dominance in the freezing southern...
  24. B

    Cholesterol and CIS Double Bonds

    anyone have an idea?
  25. B

    Cholesterol and CIS Double Bonds

    Ok someone tell me if I understand the concept correctly. Two factors determine the fluidity of the cell membrane 1) The CIS double bonds determine the fluidity of the membrane. The more cis double bonds you have, the more fluid the cell membrane will be. 2) cholesterol plays an...
  26. B

    Biology help please

    what is the difference between amino acids on their own and amino acids that have been incorporated into a polypeptide chain? My answer is that amino acids on their on do nothing. However when they interact they create a protein which eventually takes on a particular function. why does...
  27. B

    Amino acids on their own vs in a polypeptide chain?

    Bio Help! what is the difference between amino acids on their own and amino acids that have been incorporated into a polypeptide chain? My answer is that amino acids on their on do nothing. However when they interact they create a protein which eventually takes on a particular function...
  28. B

    Series representation and other problems

    Thank You AKG, I need help with the following problem if you care to assist. the integral of 2 sin(lnx)+ 1/x. u=ln(x). du=1/x so 2sin(u)+du=-2cos(u)+u=-2cos(lnx)+ln(x) also the integral(from pi/2 to 0) of sinx+tanx. I get this is really sin(x)+sin(x)/cos(x). so u=cos(x). du=-sinx dx...
  29. B

    Series representation and other problems

    \displaystyle{\lim_{n\to\infty}\frac{n}{\sum_{k=1}^n\frac{1}{k(k+2)}}}
  30. B

    Series representation and other problems

    find the series for sin(x)/x. I believe this would just mean dividing the series representation of sin(x) by x, therefore sin(x)/x=1-x^2/3!+x^4/5!-x^6/7!...=sigma(x^2n/(2n+1)!) how then would we find the radius of convergence and interval of convergence. is the series n/sigma(1/k(k+2))...
  31. B

    Help-physics to get started

    Hi Doc Al, Almost solved it the a i use here will be angular acceleration so net torque=T*R or Ia=T*R Ia=(mg-mRa)R Ia=mgr-mR^2a Ia+mgR^2a=mgr a(Ia+mR^2)=mgr a=mgr/I+mR^2 for acceleration the tension is a=mR^2g/(I+mr^2)
  32. B

    Help-physics to get started

    An object of mass m is tied to a light string wound around a wheel that has a moment of inertia I and radius R. The wheel bearing is frictionless and the string does not slip. find the tension and the acceleration of the object. I think mg-T=ma and that I=MR^2 thats all i know can...
  33. B

    Help-santa claus problem

    ok i understand. What i don't understand is how to write a "physics story". I guess that i have to describe what's going on in the problem?
  34. B

    Help-santa claus problem

    Chubby Santa(mass 100kg) decides to have some fun and slides 9.0 m down a snowy roof)starting from rest. There is a 135 n fricitional force between santa and the roof. After sliding the 9.0 meters he collides with and clings to, an elf (mass 50kg) who was sitting on the roof edge. They both fall...
  35. B

    Check answer for momentum prob

    yah i got the answer as -.57m/s. thnx
  36. B

    Check answer for momentum prob

    then i would get a negative v since v'=325-450/40=-3.125m/s
  37. B

    Check answer for momentum prob

    so the m_{2}v_{2) becomes negative? i don't understand what u mean by "direction matters"
  38. B

    Check answer for momentum prob

    A 130-KG tackler moving at 2.5 m/s meets head on(and tackles) a 90 k-g halfback moving at 5.0 m/s. What will be their mutual speed immediatley after the collison? someone please check my work m_{1}v_{1}+m_{2}v_{2}=v'(m_{1}+m_{2}) so v'=\frac{325+450}{220} v'=3.52 m/s
  39. B

    Billiard ball Momentum help

    Hey Doc Al, thnx for helping me through this process :). I got \theta_{2}=-33 v'_{B}=.81 m/s
  40. B

    Billiard ball Momentum help

    yes i plugged in numbers and i got .068=v'_{B}\cos\theta'_{2 -.72=v'_{B}\sin\theta'_{2} thats all i can do to simplify
  41. B

    Billiard ball Momentum help

    can someone help me in simplifying these equations? thnx
  42. B

    Billiard ball Momentum help

    well I am not sure whether this problem has a definite answer(as in 1.2 or 3.4 etc)or whther I am suposed to solve in terms of variables
  43. B

    Billiard ball Momentum help

    A billiard ball of mass m_{A}=0.400kg moving with a speed v_{A} =1.8m/s strikes a second ball, initially at rest, of mass M_{B}=0.500kg. As a result of the collision, the first ball is deflected off at an angle of 30\deg with a speed of v'_{A}=1.1 m/s. a) taking the x-axis as the positive...
  44. B

    Spring help-please

    So the kinetic energy would be 1/2*184(0.052)^2=.25J
  45. B

    Spring help-please

    so the total energy would be 1/2 KA^2
  46. B

    Problem of Springs

    thnx a lot man
  47. B

    Problem of Springs

    yes but i get v=0 when i do the derivative. is this correct? thnx for ur help
  48. B

    Problem of Springs

    ok so i have to take the derivative x=3.0\cos(5\pi t+\pi) so the derivative of that would be 3.0*-\sin(5\pi(0.5)+\pi)*d/dx(5\pi(0.5)+\pi
  49. B

    Problem of Springs

    yes i need to calculuate velocity, but i don't know how to get it.
  50. B

    Problem of Springs

    I have no idea what you are talking about? are my other answers correct?
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