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  1. H

    Insulating spherical shell prob!

    A small, insulating, spherical shell with inner radius a and outer radius b is concentric with a larger insulating spherical shell with inner radius c and outer radius d. The inner shell has total charge +q distributed uniformly over its volume, and the outer shell has charge -q distributed...
  2. H

    Point Charges

    ohh i understand now! thankyou@!!!
  3. H

    Point Charges

    A point charge q1 -4 nC is at the point x = 0.600 m, y = 0.800 m, and a second point charge q2 +6 nC is at the point x = 0.600 m, y = 0. I need to calculate the magnitude of the net electric field at the origin due to these two point charges. |...
  4. H

    How would I calculate the magnitude of the electric field?

    An electron is released from rest in a uniform electric field. The electron accelerates vertically upward, traveling 4.50 m in the first 3 us (microsecond??) after it is released. Part A What is the magnitude of the electric field? How would I calculate the magnitude of the electric field...
  5. H

    Charged Balls

    Then I would believe that both A and D are negatively charged and when placed near eachother they will repel?
  6. H

    Charged Balls

    There is a ball (A) is carrying a uniformly distributed unknown charge(wich may be zero) and an uncharged copper ball (D). A positive test charge (T) experiences highly attraction with ball (A) and (D). What is the nature of the force between balls A and D if they are brought very close...
  7. H

    Speed of Heartwall in body

    would f2 = the given 90 beats and f0 = the given frequency? 1.95x10^6? v = given speed of sound in body 1500 m/s after when i used those , i get an answer that is very very big.
  8. H

    Speed of Heartwall in body

    I used the second equation that you have explained; however this time I get .069227 here is what I did 1500/(1500+Vheart) * 1.95x10^6 = 90 + 1.95*10^6 Am I using the equations incorrectly?
  9. H

    Speed of Heartwall in body

    A sound wave travels at a frequency 1.95 Mhz through a pregnant woman's abdomen and is reflected from the fetal heart wall of her unborn baby. The heart wall is moving toward the sound receiver as the heart beats. The reflected sound is then mixed with the transmitted sound, and 90.0 beats per...
  10. H

    Ear Damage from a Small Firecracker

    So the area is not a circle?
  11. H

    Ear Damage from a Small Firecracker

    Lets say there is a small firecracker that emits 1200 of peak power. What is the peak intensity B in decibels at a distance of 1 m from the firecracker? This is what i have tried: B = 10log(I/Io) I = 1200/pi Since I = power/area and the area is pir^2, pi(1m)^2 Io=( 10^-12...
  12. H

    Wire problem

    humm so the general formula for lambda should be ns right? so that would make Tension = (m/s)(nsf)^2 ? however, in this problem is it possible to find the value of n?
  13. H

    Wire problem

    Whoops, I meant Tension = (m/s)((lambda)f)^2 From my notes, I have k= 2pi/(lambda) = 2pif/v Then I tried Since v = omega/k (m/s)(omega/k)^2 = Tension Since omega = 2pi/f (m/s)(2pif/k)^2 = Tension now I am stuck with k I cant seem to find a way that allows k or lambda...
  14. H

    Wire problem

    For the first part, solving for T , I get Tension = (lambdaf)^2/(m/s) Second part, Im still stuck with (lambda)f Does this mean I have to solve for lambda in using terms such as the s?
  15. H

    Wire problem

    A wire with mass (m) is stretched so that its ends are tied down at points a distance (s) apart. The wire vibrates in its fundamental mode with frequency (f) and with an amplitude at the antinodes of (A). [] How would I compute for the tension of the wire? since f =...
  16. H

    Probability and Multinomial Coefficients

    Oh now i understand the first problem, it is similiar the the deck of cards problem where there is 13 face values and 4 suits. So 4*13 = 52 facevalues. But in this problem instead of face values and suits, we have different variables and turns out to be 3*3*2 = 18 tests? Is that...
  17. H

    Probability and Multinomial Coefficients

    For the first question would it be correct if it was 3!*3!*2!? For my second question, would it be correct if it was 4! * 4?
  18. H

    Probability and Multinomial Coefficients

    Another question, how man ways can 8 people be seated in a row if there are 4 married couples and each couple must sit together? First since there is 4 couples, there can be 4! ways to sit Second since each couple can switch seats with each other, that gives it another 4! so the final...
  19. H

    Probability and Multinomial Coefficients

    An experimenter wishes to investigate the effect of three variables, pressure, temperature, and the type of catalyst, on the yield in a refining process. If the experimenter intends to use three temperature settings and three pressure settings and two types of catalysts, how many experimental...
  20. H

    Ant on a Tightrope

    g/ ( ( ( (2pi)(sqrt(T_s/mu) ) / (lambda) )^2 ) that is what i got for A min, would that be correct?
  21. H

    Amplitude of a Wave

    oh nevermind I just found the thread to this problem https://www.physicsforums.com/showthread.php?t=76470&highlight=ant+tightrope
  22. H

    Amplitude of a Wave

    anyone please?
  23. H

    Amplitude of a Wave

    anyone please?
  24. H

    Amplitude of a Wave

    A large ant is standing on the middle of a circus tightrope that is stretched with (T) tension . The rope has mass per unit length (u). Wanting to shake the ant off the rope, a tightrope walker moves her foot up and down near the end of the tightrope, generating a sinusoidal transverse wave of...
  25. H

    Superposition of waves

    Humm from what i see, it seems that the wave its moving vertically, oscillating. Is that correct? I am not too sure how to graph these. I graphed sin(x)cos(0.01) and then sin(x)cos((1/12)*(2pi))
  26. H

    Superposition of waves

    After finding the superposition forumla for Asin(kx-wt) and Asin(kx+wt), which is 2Asin(kx)cos(wt), How do I tell which direction is the wave traveling?
  27. H

    Superposition of waves

    anyone please?
  28. H

    Superposition of waves

    oh i saw where i made my mistake the answer should be 2Asin(kx)cos(wt)? Now after I get that how would I find the ye(x), called the envelope, depends only on position and yt(x) depends only on time yt(x) should be a trigonometric function of unit amplitude. I need to express...
  29. H

    Superposition of waves

    Humm would I use this identity sin(A + B)= sinA cosB + cosA sinB so Asin(kx-wt) = -AsinkxAcoswt -AcoskxAsinwt Asin(kx+wt) = AsinkxAcoswt +AcoskxAsinwt But wouldnt that equal to zero?
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