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  1. U

    Balmer Series & Lyman Series

    The formula is 1/lamba = R (1/2^2 - 1/n^2) sorry if that doesnt make sense But i will put in the number 2 in n for one wavelength and infinity for the other wavelength - and then subtract the 2 answers to get the wavelength range? Is this along the right lines?
  2. U

    Radioactive Decay

    In the textbook in a previous example - it says that the C-14 activity in a living tree is 255 Bq - that is where i got that value from but i wasnt sure if i could use that value in this question - ie is it always 255 Bq in living trees?!? The half-life is in s^-1 - therefore the answer...
  3. U

    Balmer Series & Lyman Series

    Yeh but what i dont understand is how many different energy levels there are for each of the series? Like does it go on forever or does it stop at a certain number? Ie they start at n = 2 or n = 3, but where do they stop? Do they go up to infinity? Is it as simple as plugging the number in for...
  4. U

    Balmer Series & Lyman Series

    Q: What are the widths of the wavelength intervals over which (a) the Lyman series and (b) the Balmer series extend? (Each width begins at the longest wavelength and ends at the series limit.) (c) What are the widths of the corresponding frequency intervals? Express the frequency intervals in...
  5. U

    Radioactive Decay

    Q: A 50-g chunk of charcoal is found in the buried remains of an ancient city destroyed by invaders. The carbon-14 activity of the sample is 200 decays/min. Roughly when was the city destroyed? A: I used R = Ro*e^(-lambda*t) and t1/2 = ln2/lambda t1/2 = 3.834*10^-12 s-1 and 200...
  6. U

    Minimum amount of energy necessary to remove a proton from 42-Ca atom

    Q: What is the minimum amount of energy necessary to remove a proton from the nucleus of a 42-Ca atom, thereby converting it into a 41-K atom? The former has a mass of 41.958618 u, the latter 40.961825 u, and the hydrogen atom has a mass of 1.007825 u. My answer: 42-Ca --> 41-K + 1-H...
  7. U

    Frequency of EMR

    This is what my demonstrator told me to use?
  8. U

    Frequency of EMR

    Can some please review this question and tell me if the working looks correct? Please advise of any mistakes i may have made. Thanks Q: UV radiation (wavelength = 250 nm) falls on a metal target, and electrons are liberated. If the maximum kinetic energy of these electrons is 1.00*10^-19 J...
  9. U

    Approximate the minimum kinetic energy of an electron

    Q: Approximate the minimum kinetic energy of an electron confined to a region the size of an atom (0.10 nm) How would one go about solving this? What equations/principles are involved and how do we use them? Seems like a simple question but i have no idea where to start? :confused...
  10. U

    Electrical Potential Energy

    I dont know how to do it - with the small amount of info given? Can someone show me how to work it out please? Thanks! :smile:
  11. U

    Gauss' Law and Flux Question

    What happens in each of the situations though? i.e in parts a) b) and c) - what is different in each of them? And how do you explain these observations in terms of Gauss' Law and Flux? Thanks :smile:
  12. U

    Cell Membrane Question

    The membrane of a cell is electrically equivalent to a parallel plate capacitor. A typical cell has a spherical shape with a radius 10 μm and it has a potential of −60 mV with respect to outside. The thickness of the membrane is about 0.01 μm, and it has a dielectric constant of 2. Find: (a)...
  13. U

    Electrical Potential Energy

    I have no idea what principles i am supposed to use in this question? Could someone show me how to do this question please? Thanks :smile: Calculate the electrical potential energy of two protons separated by 1 nm, and compare it with their gravitational potential energy. Estimate how heavy...
  14. U

    Gauss' Law and Flux Question

    I dont really understand Gauss' law - any help with this question would be appreciated? Coaxial cables are made of a copper wire in the center and a concentric cylindrical shell of copper outside, with insulating material in between and outside the shell. The charge per unit length of the...
  15. U

    Blood Transfusion!

    how does this find the height? I thought this involved Poisieulles Equation to find L?
  16. U

    Blood Transfusion!

    Hi, i dont know how to do this question - some help would be appreciated. Q: A patient is to be given a blood transfusion. The blood is to flow through a tube from a raised flexible bag to a needle inserted in the vein. The inside diameter of the 40mm-long needle is 0.40mm and the required...
  17. U

    Water flowing in a pipe

    Does anyone have any ideas on how to explain part b to this question? What would you say? Thanks
  18. U

    Water flowing in a pipe

    So i let R = 0.8 on one side, and the final pressure as what im trying to find, and then on the other side i let R=1 as thats at the initial radius, and let the pressure equal 1 here asell and then solve for Final Pressure? Thanks!
  19. U

    Ice cube in a glass of water

    So what i have sounds right?
  20. U

    Water flowing in a pipe

    I need some help with this question. Q: Poiseuille's equation shows that for laminar flow the volume flow rate through a pipe in proportional to the product of the pressure difference and the fourth power of the radius. The viscosity of water is 1.0*10^-3 Pa.s a) Water in a pipe is flowing...
  21. U

    Ice cube in a glass of water

    Some help with this question please? a) An ice cube floats in a glass of water. When the ice melts, will the water level in the glass rise, fall, or remain unchanged? Justify your answer. b) If the ice had been made from pure water, and the water in the glass was salt water (denser than...
  22. U

    Vertical SHM

    Sorry - i didnt read your later posts!
  23. U

    Vertical SHM

    Using the answer from the quadratic is obviously not the amplitude - it was incorrect. So where do i go from here? What does the speed of the plate have to do with the amplitude? The total mechanical energy of the scale at the point of maximum displacement is given by 1/2*k*A^2 , where k is the...
  24. U

    Vertical SHM

    So is this positive x value now the displacement after the ham hits the plate? Is it also the amplitude or is this just the new equilibrium position from where the plate and ham are at rest?
  25. U

    Vertical SHM

    Im not sure if im doing the right thing here? :eek: Can anyone show me how this question is solved?
  26. U

    Vertical SHM

    So then U = mg(h+x) therefore: 0.3*9.8*(0.25+x) = 1/2*200*x^2 So then do you solve for x, using the quadratic formula? I get x = 0.455 or x = -0.16 Which one would then be the displacement? I got these answers from: 100x^2 - 29.4x -7.35 Am i doing the right thing now?
  27. U

    Vertical SHM

    But then if mgh = 1/2kA^2 that means for the ham: 0.3*9.8*0.25 = 1/2*200*A^2? I dont understand? Ive done that before but it doesnt work? But what you are saying is to work out how far the ham goes past the 0.25m? I still dont understand how to get that?
  28. U

    Vertical SHM

    Sorry can you show how to find x - the lowest position (after the ham hits it)?
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