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  1. rakeru

    Finding Constants to Solution Given 2nd Order, Nonlinear DE

    Alright, I ended up with A=+/- 1 and B=1/sqrt(2).
  2. rakeru

    Finding Constants to Solution Given 2nd Order, Nonlinear DE

    Ahhh yes. I understand! Thank you very much :)
  3. rakeru

    Finding Constants to Solution Given 2nd Order, Nonlinear DE

    I keep getting that phi is zero.
  4. rakeru

    Finding Constants to Solution Given 2nd Order, Nonlinear DE

    The second derivative is phi''=-2AB^2tanh(Bx)sech^2(Bx)= -2AB^2tanh(Bx)+2AB^2tanh^3(Bx) and so tanh(Bx)[2AB^2-A]+tanh^3(Bx)[-2AB^2+A^3]=0
  5. rakeru

    Finding Constants to Solution Given 2nd Order, Nonlinear DE

    d^2phi/dx^2= -2AB^2tanh(Bx), correct? Now I have gotten the equation tanh(Bx)[2AB^2-A+A^3tanh^2(Bx)]=0 I set 2AB^2-A+A^3tanh^2(Bx)=0 tanh(Bx)= sqrt[2B-1]/A But now what? Was I supposed to change the tanh^2(Bx) into 1-sech^2(Bx)?
  6. rakeru

    Finding Constants to Solution Given 2nd Order, Nonlinear DE

    Homework Statement Okay, here's the deal: I have been given a second order nonlinear differential equation, and I have also been given the general solution with constants A and B. I am supposed to find the constants A and B. The solution represents a fermion at rest, since the solution does...
  7. rakeru

    Recommendation Moral Dilemma

    Hello! I am wondering if anyone can help me decide what to do about this problem. I'm at a college majoring in physics, and I'm almost done with my two years. I'm applying to different universities,and I have a professor that wishes to write me a recommendation for when I transfer. He asked me...
  8. rakeru

    Is the Derivative of a Function a Differential Equation?

    I am talking about first order ones.. I don't know how to solve second order ones.
  9. rakeru

    Is the Derivative of a Function a Differential Equation?

    Is the derivative of a function a differential equation? I guess it would be because it involves a derivative, right? Would the solution to the equation just be the original function? Is solving a differential equation just another way of integrating? Like with finding solutions of separable...
  10. rakeru

    Rolling Ball and Proportionality Between Distance and Time

    Thanks a lot. I didn't know it was so complicated. Thanks again.
  11. rakeru

    Rolling Ball and Proportionality Between Distance and Time

    Homework Statement A ball starts from rest and rolls down a hill with uniform acceleration, traveling 130m during the second 6.0s of its motion. How far did it roll during the first 6.0s of motion? Homework Equations I guess: v=v(0)+at v^2=v(0)^2+2ay x=x(0)+v(0)t+0.5at^2 The Attempt at...
  12. rakeru

    Two values for m for which a line is tangent to a parabola

    Homework Statement Hi! I am doing some problems to practice for a math competition, and I'm wondering if I did this correctly. I don't really have an answer sheet, so I have no way of knowing whether I'm right. If you would please review it, that would be cool! It reads: There are...
  13. rakeru

    Schools French Universities For Physics

    Hello! I'm wondering if anyone knows any universities in France that have a great physics department. I'm currently in my second year of college getting my associates degree, and I'm looking at options in France for my bachelors. My French professor is always talking about French...
  14. rakeru

    Does it matter if L + epsilon is not in the range of the function?

    Uhm, okay. So... who is right??? I don't quite understand what L-ε < f(x) < L -ε means. Do you mean L - ε < f(x) < L + ε ???
  15. rakeru

    Does it matter if L + epsilon is not in the range of the function?

    Homework Statement Use a graphing calculator to find \delta when 0<|x - \pi/2|<\delta and |sin(x) - 1|<0.2 Homework Equations I don't think there are any other than the format of the previous information: 0<|x-a|<\delta and |f(x)-L|<\epsilon The Attempt at a Solution Okay...
  16. rakeru

    Finding the point where the net electric field is zero

    Oh, okay! Thank you very much! :)
  17. rakeru

    Finding the point where the net electric field is zero

    Homework Statement The question wasn't really written down. It was a question asked after an explanation, and it really wasn't straightforward. I'm going to try to make it into a intelligible thing. If there is a +3 charge and a -1 charge at a distance from one another, where to the right...
  18. rakeru

    Finding a Coefficient in an Expansion (n-j is negative?)

    Oh my god! Yes! I see!! Thank you!!! I wonder why my teacher did it like that, though. Thanks! :)
  19. rakeru

    Finding a Coefficient in an Expansion (n-j is negative?)

    In that case, j would be just four, right?
  20. rakeru

    Finding a Coefficient in an Expansion (n-j is negative?)

    Hmm well.. that's how my professor did it. So after trying multiple times with different values for n and j, I got the right one. I ended up using n=7 and j=4. At first I tried n=14 and j=8. Nope. Then, I tried n=14 and j=4. Nope. Then, I tried n=7 and j=4! It worked... I'm still not so sure...
  21. rakeru

    Finding a Coefficient in an Expansion (n-j is negative?)

    Homework Statement Find the coefficient of x8 in the expansion of (x2-3)7 Homework Equations This one: (n n-j) an-jxj The Attempt at a Solution Hi! Well, I know that x= x2 a= -3 n= 7 and apparently, j=8. This is what confuses me. n-j is a negative number.. how would...
  22. rakeru

    History of Physics

    Thank you so much :) I'm going to check it out :)
  23. rakeru

    History of Physics

    Hello! I've recently begun to read a lot of nonfiction books. I'm currently reading a book about stories told by Richard Feynman about his amazing life. It's hilarious and so clever. I would absolutely LOVE to read a book on the history of physics!! I think it's really fascinating. Could...
  24. rakeru

    Tension and Acceleration with a Pulley and Two Masses

    I mean, I think it would be equal.. but I'm not sure. Apparently it would be zero if the string has negligible mass.
  25. rakeru

    Tension and Acceleration with a Pulley and Two Masses

    Homework Statement If there is a mass on a frictionless table connected by a string to another mass hanging from a pulley off the side of the table, is the net force on the string zero? Is the force of tension equal on both sides if the system is accelerating? Would both objects accelerate...
  26. rakeru

    Pre-Calculus and Trigonometry

    Hmm... Everyone I know at my school avoids math like if it were a disease. If I take them separate, I'd pay around a hundred dollars more. I'm guessing that wouldn't be much of a problem. Yeah, I totally need to take them. I'm thinking of taking both separately. I need to take them in the...
  27. rakeru

    Pre-Calculus and Trigonometry

    Hi! I am currently taking a math class called college algebra. Here's the little description thing: MAC1105 - This course introduces the student to the concept of functions and their graphs. Students will graph linear, quadratic, rational, exponential, logarithmic, radical, power, and...
  28. rakeru

    Why do people say that the person would be weightless?

    I don't understand that, but hopefully in the future I will.. I guess if the object is on the surface I would just use mg, but if the object is far from the surface I'd use GmM/r^2 ?
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