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  1. U

    Gauss' Law Help

    This Q is actually the charge on the outer surface (d) . For inner surface (c), it will be negative of the charge on solid sphere. Add both of these to get the net charge. That will be the answer to (b)
  2. U

    Finding the wave speeds

    v=√(T/¢) T= tension in wire ¢= mass per unit length
  3. U

    Gauss' Law Help

    Go ahead and use it. See if you can get the answer. (∫E.dS=q/ε(o)) or you could simply use the formula you mentioned it in relevant equations. I'm not supposed to spoonfeed you. Check the answer in your textbook.
  4. U

    Gauss' Law Help

    Assume that the solid sphere and induced charges are not present at all (since the have no effect). Only a spherical conductor is present with charge on its outer surface.
  5. U

    Gauss' Law Help

    Your answer to b part is wrong. There will be induced charge on the inner surface of the shell so that the field due to solid sphere and induced charge is 0 everywhere outside it. So the field at 50 cm is only due to the charge on outer surface. Use it to calculate net charge on shell.
  6. U

    Show that Euler-Mascheroni sequence is decreasing &monotonic

    What if you integrate it from n to n+1? Also can you think of the area of rectangle formed with height 1/(n+1) and width (n+1)-n? Just compare them on the graph of f(x)=1/x
  7. U

    Lagrange's mean value theorem problem

    Yah... Was just thinking the same and was about to post it... :P
  8. U

    Lagrange's mean value theorem problem

    But your h(x) had solved the problem. What was the error??
  9. U

    Lagrange's mean value theorem problem

    Thanks mate!! Solved it... But how did you think of that function h(x)??
  10. U

    Lagrange's mean value theorem problem

    Homework Statement Homework Equations Lagrange's mean value theorem The Attempt at a Solution Applying LMVT, There exists c belonging to (0,1) which satisfies f'(c) = f(1)-f(0)/1 = -f(0) But this gets me nowhere close to the options... :(
  11. U

    Definite integration problem

    Oh yah... Thanks ... I solved it... But have a look at this file... I couldn't get an answer for this...
  12. U

    Definite integration problem

    Oh yes... By mistake i typed the integration symbol after it. Cosec a should be inside the integral. So, how should i proceed??
  13. U

    Definite integration problem

    Homework Statement ∫dt/(t^2 +2tcos a + 1) (Limits of the integral are from 0 to 1) (0<a<π) Homework Equations The Attempt at a Solution Put t=sin a dt=cosa da ∫dt/(t^2 +2tcos a + 1) = ∫cos a da/(sin^2 a + sin 2a + 1) [ limits of integration changed to 0 to π/2] = ((cosec a)/2) ∫sin 2a...
  14. U

    Does the colour of light change with a change in medium

    Thanks!! www.physicsforums.com/showthread.php?t=459065 this thread also helped me. Thanks for giving the link.
  15. U

    Lens maker's equation used correctly?

    @Danny :the equation which you are using seems to be derived from thin lens equation where you neglect thickness as it's too small compared to Radii of curvature.
  16. U

    Lens maker's equation used correctly?

    When I calculated the answer, it came out to be 40.9 cm. Strange!! I used the lensmaker equation given in Wikipedia. These were my results : f= 900/37 cm, u=-60 cm (given) So, using lens formula v = 40.9cm. And yes you need to use the thickness. See the lensmaker's equation in Wikipedia!!!
  17. U

    Does the colour of light change with a change in medium

    Homework Statement This is just my doubt and not really a question. We know that speed of light changes upon change in medium of propagation. Its wavelength also changes. But its frequency doesn't change. So, does the colour of light change upon change in the medium of propagation...
  18. U

    Lewis acids and bases

    hi all! I am not able to understand what's a Lewis acid and a Lewis base. tell me if these are Lewis acids or Lewis bases and tell me the reason. HCl, H2SO4, H3PO4, CO2, HCN. my approach: first 3 I'm not able to decide. 4th one I thought to be Lewis base as 2lone pairs of electrons left in...
  19. U

    Change in velocity of light with change in optical density

    hey guys! we know that velocity of a wave = wavelength x frequency. and speed of light changes with change in optical density. so there must be change in either frequency or wavelength or both. which of these quantities change with change in optical density? and why?
  20. U

    Propagation of light as wave

    thanks for replying and explaining. :-)
  21. U

    Propagation of light as wave

    huy there! everyone says that light has wave particle duality. it means light is a wave and also consists of a particle. now, wave is a disturbance in a medium. but, we know that light can travel without a medium. then why do we say it is a wave? (i know that it is a non mechanical wave then why...
  22. U

    A small postage stamp is placed in front of a concave mirror

    hey i have helped you out in my previous post atoreta88. if you still have problem then post it.
  23. U

    A simple projectile question

    i cannot believe what a silly mistake i was doing. i was taking everything in feet and second but was taking acceleration in y direction in metre/second square. now i have solved the problem and got the correct answer. the acceleration should be 33 ft/s^2 (approx.).
  24. U

    A small postage stamp is placed in front of a concave mirror

    first of all what type of image are you talking about. is it real or virtual? if it is a real image: (a) do you know where the image lies if the object is at centre of curvature? aren't image and object at the same distance from the pole of mirror. if you exactly know what 'R' is, then you...
  25. U

    Why artificial gravity is not possible?

    i totally agree with what cjameshuff said. scientist are looking forward to build a rotating spaceship to send people to mars thus reducing the risk of muscle weakening or decay.
  26. U

    A simple projectile question

    yah, if the question asks for that then i am done with the problem. it's quite easy. thanks a lot!
  27. U

    100 hotel rooms and 100 guests?

    thank you very much !!!!!!!!!!!!!
  28. U

    A simple projectile question

    ok i have proceeded in this way. just check where am i wrong:- u (in both x and y directions) = 64/root 2 feet/sec distance of the ball from goalpost = 40 yards = 120 feet a (in x direciton)=0 therefore, 120 = 64/root 2 x t + 1/2 x 0 x t^2 => t = 15 x root 2 / 8 second therefore, s (in y...
  29. U

    Electric field and work done

    well i have a suggestion for you. first, read the question carefully and note down all the bits of information. like in the above case: work done and charge. then think of an equation relating the information and the question. this will help a lot.
  30. U

    Combination and permutation

    thank you! but the second one has been done correctly by lanedance. in that one the second block which i mentioned is not a block so the correct answer is that of lanedance. check that out
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