What is Unknowns: Definition and 155 Discussions

The Tomb of the Unknown Soldier is a monument dedicated to deceased U.S. service members whose remains have not been identified. It is located in Arlington National Cemetery in Virginia, United States. The World War I "Unknown" is a recipient of the Medal of Honor, the Victoria Cross, and several other foreign nations' highest service awards. The U.S. Unknowns who were interred are also recipients of the Medal of Honor, presented by U.S. presidents who presided over their funerals. The monument has no officially designated name.

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  1. E

    Nodal Analysis 1 equation 2 Unknowns Problem

    http://imgur.com/W9sWTv7V=IR, that is all I think 3. I have put my ground at the bottom branch. I have tried to write a KCL for the top branch but end up with 0=0 when I substitute in equivalencies. My KCL: (V1+5Ix-0)/20+2+Ix=0. (V1+5Ix)/20=-2-Ix. So 0=0. I am not sure if I am writing my KCL...
  2. K

    Using the ideal gas law with two unknowns

    Homework Statement You are given a closed container containing a single atom ideal gas. The volume is V1= 0,45*10^(-3) m^3 Pressure p1 is 3,2 MPa Temperature, T1, is 892 K The volume of the gas is increased to V2= 8*V1 Find the pressure and temperature after the increase of volume...
  3. G

    Statics problem - too many unknowns?

    Homework Statement See attachment. Find the tension in the string that is keeping this weird contraption together. The left stick has mass m, the right stick has mass 2m. m, θ and L are known quantities. Homework Equations The Attempt at a Solution Tried starting with the right...
  4. E

    MATLAB MATLAB 3 equations and 3 unknowns

    Hello, I have never really used MATLAB before, and I was assigned some homework on it. While I was able to solve most of them, I was unable to solve this one in particular, even after searching the internet and documentation, there was many kinds that I was left confused. Does anyone know...
  5. S

    3 x 3 matrix with unknowns. Conditions for invertibility.

    I've attached 2 images above. The first is the problem itself and the answer. It's question 9. So, I tried solving this question using the method of finding the inverse of a n x n matrix by augmenting it with the identity matrix of the same dimensions and then applying row ops in an attempt to...
  6. J

    Linear Algebra, Cramers Rule - Solving for unknowns in a matrix

    Hello everyone, I have a linear algebra question regarding Cramer's rule. Homework Statement Using Cramer's rule, solve for x' and y' in terms of x and y. \begin{cases} x = x' cos \theta - y' sin \theta\\ y = x' sin \theta + y'cos \theta \end{cases} 2. Homework Equations ##sin^2 \theta...
  7. T

    Number of unknowns - Coordinate Transforms

    In general relativity, what are the total number of unknowns for a generic coordinate transform? Is it just 4 * 4 = 16? Is there a way to break those down into combinations of types, such as boosts, rotations, reflections (parity?), etc, or is it just left wide open from an interpretive...
  8. D

    Confused About Solving 3 Unknowns Using Given Formulas | Step-by-Step Guide

    Homework Statement Hello all, I'm trying to solve for 3 unknowns x,y,z. We are given these formulas: http://screencast.com/t/Y8QobUXVB3S3 Homework Equations Please see link provided above. The Attempt at a Solution I first rearrage for root(x) then I rearrange equation 2 for root(y), I...
  9. D

    First Chapter of Text: distance formula with unknowns (13x,-23x) (6x,x) x>0

    Homework Statement Find the distance between P and Q P(13x,-23x), Q(6x,6), x>0 *This came from Chapter 1 Linear Functions, Equations, and inequalities Section 1.1 Real Numbers and the Rectangular coordinate System of A Graphical Approach to Precalculus with Limits by Hornsby et alHomework...
  10. Z

    Understanding Algebraic Unknowns in Physics Problems

    Homework Statement The unknowns below read as "m sub 1", "rub sub 2" etc. The maths part of a physics problem states: r1/v1 = r2/v2 Combining these with equation : m1r1 = m2r2 gives: v1/v2 = r1/r2 = m2/m1 Homework Equations The Attempt at a Solution Would anyone be able to explain to me...
  11. S

    Solving equation with two unknowns?

    Hello, Okay, I have finally worked out a decent curve to work with which is in accordance with my previous post called "How to create a simple mathematical model". According to the attachment in this thread, I have deemed the following equation format as respective to the curve in my...
  12. W

    What Secrets Could a Giant Spaceship Uncover in Saturn's Rings?

    I am using this in a science fiction novel I am working on for National Novel Writing Month, most of my novel is "soft" but I want to know what we could actually know in this situation. If it helps any the spaceship is about the size of 20 Earths and its going through Saturn.
  13. P

    Multiplying matrices with unknowns

    |1 | |4| |0 | |5| |1| |6 | A|-1 |= |5| ' A |-1|= |3| and A |1|= |8 | |0 | |0| | 1| |5| |1| |11| The first question is, determine the dimensions of A. So I can tell it is a 3x3 Then I'm asked to determine the columns of A, I'm not sure about...
  14. J

    How is it possible to solve this system of 2 equations with 4 unknowns?

    I've always been taught that to solve for 4 unknowns, you need 4 equations. This question seems to suggest that there are in fact solutions. Here's the problem and my work so far. The most I can seem to do is eliminate one variable, I'm not sure how to shake a second one out, let alone all 4.
  15. Hepth

    Error propagation with two functions, two unknowns.

    If I have two independent variables x,y, and two measurements, m1, m2 with errors. And the dependence is thus: m_1 \pm \delta m_1 = f[x,y] m_2 \pm \delta m_2 = g[x,y] Now in my case, f and g are complicated expressions of x and y with no simple solution. (Actually I think i can...
  16. M

    Question on reducing 3 equations with 3 unknowns

    Say I have a system of equations of the following form: a_1 A^2 + b_1 B^2 + c_1 C^2 + d_1 = f_1 a_2 A^2 + b_2 B^2 + c_2 C^2 + d_2 = f_2 a_3 A^2 + b_3 B^2 + c_3 C^2 + d_3 = f_3 Where a,b,c,d,f are coefficients, and A,B and C are unknown variables. 1. Can we write them in terms of two variables...
  17. B

    Solving set of non-linear equations with two unknowns in MATLAB

    Hi, I have two non-linear equations with two unknowns, i.e., tau and p. both equations are: p=1-(1-tau).^(n-1) and tau - 2*(1-2*p) ./ ( (1-2*p)*(W+1)+(p*W).*(1-(2*p).^m)). I am interested to find the value of tau. After doing some research on internet I came to know that these...
  18. K

    Simultaneous equations with 3 Unknowns

    Help chaps I am having a bad time with this. I can appreciate this is basic, however i can not get my head around it. Im scrubbing up on my maths as i was thinking of doing a HND in Engineering. I am working my way through K.A. Stroud's Engineering Mathematics and simply can't get to grips...
  19. O

    Projectile Motion So many Unknowns

    Homework Statement Need Help I have been trying to solve this problem for a while now. I know the quadratic formula has to be used in order to solve this problem but I am having trouble getting started. Question A soccer ball is kicked from the ground level at an angle, such that the wall is...
  20. F

    Finding relative velocity when there are multiple unknowns

    Homework Statement Two spaceships, each measuring 300 m in its own rest frame, pass by each other traveling in opposite directions. Instruments on board spaceship A determine that the front of spaceship A requires 1 microsecond to traverse the full length of B. What is the relative velocity...
  21. M

    Elastic 2D Collision with Lots of Unknowns

    Homework Statement Mass m1, moving to the right, collides with mass m2, which is at rest before the collision. The masses are m1 = 0.1 kg and m2 = 0.2 kg. The scattering angle of m1 will be 30 degrees above the horizontal. a) Calculate the recoil angle phi of m_2. b) Calculate the recoil...
  22. S

    MATLAB Equation with 3 unknowns. how do i find the maximum solution using matlab?

    Equation with 3 unknowns. how do i find the maximum solution using matlab?? Hello, Im stuck in matlab, i have an equation with 3 unknowns. how can i get the maximum answer possible? Is there a way with a 3D graph?? Equation: F = ( sqrt((b^2 + c^2) -(2b c cos(y))) x M ) / (b c sin(y))...
  23. C

    Solve 3 equations in three unknowns I, W, and L

    Homework Statement Solve 3 equations in three unknowns I, W, and L to find the critical value of L. ***Please See attachment 'differential.gif'**** also note, that I wrote all this using 'mathtype', if its of importance for any to know. Homework Equations Please see attachment...
  24. Hepth

    3 Equations with 2 Unknowns

    I have 3 equations with two unknowns of the form: r_i == f_i (g,\beta) Where g and \beta are the independent unknown variables and r_i are known experimentally, but have some error associated with them, say something like 4.3 \pm 0.3 and there are other errors associated with constants inside...
  25. C

    How to graph potential energy for 2 atoms in diatomic molecule w/ 3 unknowns

    Homework Statement The potential energy of two atoms in a diatomic molecule is approximated by U(r)=a/r^12 - b/r^6, where r is the spacing between the atoms and a and b are positive constants. Find the force F(r) on one atom as a function of r. Make two graphs one of U(r)...
  26. T

    3 unknowns, 3 equations, failure on algebraic method

    Homework Statement This example comes straight out of the book. Can someone show intermediate steps? Fx = 0: -0.0933Tab - 0.0846Tac + P = 0 Fy = 0: +0.778Tab + 0.705Tac - 1962N = 0 Fz = 0: +0.622Tab - 0.705Tac = 0 Book solution: P = 235 N, Tab = 1401N, Tac = 1236N Homework...
  27. B

    3 Questions Regarding a particular system of unknowns x,y,z

    Homework Statement Ok the system we are working with is x-2y =1 x-y+az=2 ay+9z=b Homework Equations 1.)> For which values of a does the system have a unique solution? 2.)> For which pairs of values (a,b) does the system have more than one solution? 3.)>Why is it that the...
  28. F

    1 equation, 2 unknowns, need integer solution

    Homework Statement I needed to solve this single equation with two unknowns. 199x - 98y = -5 0< x <=99 0< y <=99 I typed the equation into Wolfram Alpha and got an integer solution of: x = 98n + 31 y = 199n +63 when n is an integer Since I know my restriction on x and y I can...
  29. M

    Statics machine equilibrium: support reaction- I have too many unknowns

    Please help Due in 2 hours. Statics machine equilibrium: reactions- too many unknowns Homework Statement The woman using the lat pulldown machine is holding the 80-lb weight stationary in the position shown. What are the reactions at the built-in support E and pin support F? (A and C are...
  30. P

    Three Unknowns and Three Equations

    Hi, I am working on an investigation for school and, before proceeding (or better, before trying again) I wanted to know if this would work. I have a graph and a proposed model with three variables: A/1 + Be(-Mx) x being time. Is it possible for me to find out these three unknowns...
  31. F

    What Angle Was the Second Projectile Fired to Collide with the First?

    Homework Statement A projectile is fired at an angle 60 degrees above the horizontal with a speed of 60m/s. A 0.5 second later, another projectile fired at the same speed but at a different angle. The two projectiles collide at some point (x,y). Find the angle the second projectile was fired...
  32. R

    Two unknowns in trigonometric calculation?

    Homework Statement A boat leaves the harbor going 60 degrees north-east with the speed 20km/h. 3 hours later, another boat leaves a harbor 160km to the east with a speed of 70km/h. What course should the second boat have to meet the first? Homework Equations Not 100% sure what equations would...
  33. M

    Finding partial derivative with 4 unknowns in 4 equations

    I'm trying to figure out Ch 4, Sec. 7, Q 25.c of Mathematical Methods in the Physical Sciences, 3rd Ed. It's not homework I'm working on since I'm not in school. Assume that f\left(x, y, z\right) = 0 If x, y and z are each functions of t, show that \left(\frac{\partial y}{\partial...
  34. V

    Efficient Solutions for Systems of 3 Equations and 3 Unknowns with Squares

    Hi, I'm wondering what is the quickest/easiest way to solve a system of 3 equations and 3 unknowns that involves squares. Preferably not by hand. Can I use the matrix feature on my TI84, or do I need to use software like Matlab? This set of equations came up while I was trying to solve a...
  35. M

    How can I solve 4 equations with 4 unknowns?

    Homework Statement First of all hi, I was working some mathematics and ended up with 4 unknowns with 4 equations. I tried substituting equations but ended up with squared unknowns. The following is what i ended up with so far. The Attempt at a Solution Any help on how to solve...
  36. Femme_physics

    Statics - When 2 unknowns and 2 equations cancel each other out

    I hate it when that happens, but whenever I make 2 equations and 2 unknowns, setting the sum of all torques at the known force (rather than the support) and do sum of all forces equation (either of x or y) I get complete canceling of terms and 0 = 0. What does it mean...
  37. S

    Solving for 2 unknowns, 2 equations in rectangular form

    Homework Statement Find I(a) and I(b) for the equaions below: 90 = -j5(I(a)) + j25(I(b)) 60 = (20+j5)(I(a)) - j5(I(b)) Homework Equations Equations in rectangular form The Attempt at a Solution I've tried solving this for one variable and then plugging the answer into the second...
  38. B

    Solving 3x3 Matrix: Solving 3 Equations-3 Unknowns

    Homework Statement http://img220.imageshack.us/img220/8187/questiong.jpg NOTE: I's are the unknowns, R's and emfs are given Homework Equations The Attempt at a Solution [PLAIN][PLAIN]http://img4.imageshack.us/img4/2180/solutionv.jpg Using Junction, loop rule to come up...
  39. C

    How to solve a system of 3 equations for 3 unknowns

    Homework Statement The variables of interest are : Constants are a, b, c, and g Unknowns are x, m, and L The intent is to define x, m, and L in terms of a, b, c, and g. Homework Equations The three dependent equations are : (1) x + g*m = c (2) [x / (a^2)] + L = 0...
  40. W

    Finding the Exact Location: Using Equations and Angles to Solve for Two Unknowns

    How would one go about to solve two equations with two unknows, x and y, where the two equations are of the following form: A/B = c7 where: A = (c1-x)^2 + (c2-y)^2 + (c3-x)^2 + (c4-y)^2 + c5 and B= SQRT{[c6 + (c1-x)^2 + (c2-y)^2 ][c7 + (c3-x)^2 + (c4-y)^2 ]}...
  41. T

    I/P convertor equation finding 2 unknowns

    Homework Statement Basically its all on the attached sheet as i don't know how to stick images in the post. im having trouble finding two distances x and y (x+y= 100mm) just need a little help rearranging the equation on the attached word doc. But ‘A’ passes through origin...
  42. L

    System of 4 quadratic equations with 4 unknowns

    Hi all, I am trying to generalize a geometric concept found on page 7 from Steven Weinberg's "Gravitation and Cosmology" from 2 to 3 dimensions. At the end I am stuck with the following set of equations: 1: a1+a2z32+a3z3z4+a4z42=0 2: b1+b2z32+b3z3z5+b4z52=0 3: c1+c2z32+c3z3z6+c4z62=0...
  43. C

    Solving for Hall Petch Unknowns

    The lower yield point for an iron that has an average grain diameter of 5x10^-2mm is 135 MPa. At a grain diameter of 8x10^-3, the yield point increases to 260 MPa. At what grain diameter will the lower yield point be 205 MPa? Homework Equations Hall-Petch Equation: σy = σo + ky(d^-(1/2)) The...
  44. B

    Circular motion with unknowns and picture

    Homework Statement An ice cube slides on a frictionless sphere. It is placed at the top at of the sphere with radius (R), and given an instantaneous push at speed (S). At what angle(x) from vertical does the ice cube leave the surface of the sphere? Radius = R Speed/Velocity = v angle = x...
  45. Q

    Solve for d: "Finding Unknowns in Equations with Sin and Cos

    Homework Statement I have this equation, but I'm having trouble solving for the unknown :/ I know that d is 109; I just don't know how to get it. see below Homework Equations -dsin35 = -4.9(dcos35/25)^2 The Attempt at a Solution -dsin35 = -4.9d^2 cos^2(35)/25^2 -dsin35 = -4.9d^2 cos(35) x...
  46. B

    2 equations, 2 unknowns: from hell

    Homework Statement This seemingly-innocuous system came up in a quantum mechanics problem: \left. \begin{array}{l} (1 - \sqrt 2 ){C_1} + {C_2} = 0\\ {C_1} - (1 + \sqrt 2 ){C_2} = 0 \end{array} \right] I want to find out what C1 and C2 are. Simple, right? Well... Homework Equations...
  47. L

    A system of equations with more unknowns than equations

    Hello, It is known that a system of linear equations is considered overdetermined if there are more equations than unknowns... My question simply stated: is there a term to describe a system of linear equations if there are more equations than unknowns? Google seems to struggle when my...
  48. U

    2 equations, 3 unknowns - finding 2 ratios of unknowns

    Homework Statement I have two equations with three unknowns. Obviously, this is indeterminate and not all three variables can be independently solved. However, I only need (want) to solve for two ratios of the three unknowns. I am writing greatly simplified versions of the equations below...
  49. N

    Is it possible to solve a system of three equations with two unknowns?

    Hello! How do I determine if there is a solution to the following simultaneous equation?: 2a+3b=7 5a+7b=19 9a+5b=32 I have given a specific example but I was interested in the general case. I am confused because I have seen examples with two equations and two unkowns where it has been...
  50. G

    Matrix equation with two unknowns

    Hello I have a problem regarding matrix equations. In my assigment two products of matrices are given, but none of the factors. [X]'[X] = [A] (2x2) [y]'[X] = [B] (1x2) I know how to solve a matrix equation with one unknown. AX = B and take the inverse etc. But can you give me some...
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