What is Point: Definition and 1000 Discussions

The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.
When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of substances to supercool, the freezing point can easily appear to be below its actual value. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice, that is, the melting point."

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  1. cathal84

    Show that f has a stationary point at (0, 0) for every k ∈ R

    Homework Statement Let f(x, y) = x^2 + kxy + y^2 , where k is some constant in R. i. Show that f has a stationary point at (0, 0) for every k ∈ R Homework Equations ... The Attempt at a Solution I may have the solution or i may have gone completely wrong I am not entirely sure. i first found...
  2. binbagsss

    I Scattering, 4 point correlator, number of distinct Feynman diagrams

    In order to compute the scattering probability that two particles of type 1 (associated to ##\phi_1(x)##) which come from the far past with the momenta ##p1## and## p2##, to scatter and evolve into two particles of type 2 (associated to ##\phi_2(x)##) with the momenta ##p3## and ##p4## , I am...
  3. M

    MHB Finding the x-value of Max, Min, & Inflexion Point

    i know how to do the first two parts the x value of the max is 0 and of the minimum is 8 and 4 is the x value of the inflexion point. however i don't know how to do part 3
  4. M

    MHB Stationary Points of x-2xsinx: 0-3pi

    what are the stationary points of x-2xsinx in the interval of [0,3pi] i differentiated it and let it equal to 0 . i get when i let 1-2x cosx-2sinx equal 0 i can't solve it
  5. Schaus

    Electric potential at a point due to two charges

    Homework Statement What is the electric potential at P due to charges Q1 and Q2...
  6. I

    Calculating saturation and dew point given pressure and temperature

    Hi guys and gals. Hobbyist, not a student. I've had great input here in the past. Thank you in advance for any direction and help figuring this out. -Seth- 1. Homework Statement I'd like to learn how to calculate relative humidity, saturation, and dew point under differing pressures and...
  7. A

    Work done in moving a 1C positive charge from one point to another

    Homework Statement Determine the Work done by the electric field E = axX - ay2y in moving a unit positive charge from position p1 (-2,0,0) to position p2 (5,-1,3) the distances are in m Homework EquationsThe Attempt at a Solution I'm not really experienced with forums therefore my attempted...
  8. I

    What is point of Durham tubes in a Nitrate reduction test?

    Lab manual is confusing me, and I'm not sure if its actually wrong, or the wording is bad, or if this is because I'm not understanding something. It says: "Before a broth can be tested for nitrate reductase activity it must be examined for evidence of denitrification. This is simply a visual...
  9. kelvin490

    MATLAB How to make 2D plot of points with different colors?

    I want to make a 2D plot of points with different x, y coordinates and have colors depending on a separate variable. I have make column vectors for x and y coordinates and another column containing 1 or -1. I would like to represent the points with 1 as red and -1 as blue points. I have codes as...
  10. Cocoleia

    Find the level curve through the point on the gradient

    Homework Statement Homework EquationsThe Attempt at a Solution The answer is F. I don't how to get this. I know that it is perpendicular and must have a horizontal tangent. How do I come to this answer?[/B]
  11. pesslovany

    Application of Gauss' law - point charge in hollow sphere

    Firstly I appologize, that I am not native english speaker and I don't study physics(but cybernetics we are getting just some general knowledge about physics), but hopeffuly I will write this right. Homework Statement We know that inside of a conductive object is protected from influence of...
  12. C

    I Convergence of Taylor series in a point implies analyticity

    Suppose that the Taylor series of a function ##f: (a,b) \subset \mathbb{R} \to \mathbb{R}## (with ##f \in C^{\infty}##), centered in a point ##x_0 \in (a,b)## converges to ##f(x)## ##\forall x \in (x_0-r, x_0+r)## with ##r >0##. That is $$f(x)=\sum_{n \geq 0} \frac{f^{(n)}(x_0)}{n!} (x-x_0)^n...
  13. S

    Point body of mass hung from a ceiling on two ropes

    Homework Statement An object weighing 8.0 N is supported by two rope, which form the angles a and b to the horizontal, with tensions T1 and T2. angle a = 30 degrees angle b = 60 degrees I have calculated these values: T1 = 4N T2 = 6.93N How do I find the maximum tension of the obtained...
  14. P

    MHB What Is the Nine Point Center Theorem?

    I'm having a little trouble starting on this problem. Can someone help? I was trying to solve it out, but I just ended up telling how to draw the center. Attached is the problem:
  15. R

    MHB Finding Critical Point: x for y=3e^(-2x)−5e^(-4x)

    y = 3e^(−2x) −5e^(−4x) y'= −6e^(−2x)+20e^(−4x) How do I find the critical point at x? The answer is (1/2)ln(10/3) but I don't know how to get that answer Thank you
  16. dfklajsdfald

    Finding the Value of axb on the Unit Circle | Round to the Nearest Thousandths

    Homework Statement the point (log a, log b) exists on the unit circle. find the value of axb. round to the nearest thousandths. Homework Equations x2 + y2 = 1 The Attempt at a Solution x2+y2 = 1 loga2+logb2 =1 2loga+2logb = 1 2(loga+logb) = 1 loga + log b = 0.5 logb = 0.5−loga now i try...
  17. A

    A Euler beam dynamic equation under point load

    Hi So the problem I have is I want to get the equation of motion of a vibrating beam under a nonlinear "Point" force. The equation would be like this for a distributed load (Which is not the case) But I want the load to be at a point at x=L So I have to options. Add an impulse dirac function...
  18. H

    Intensity at a point on the screen

    Homework Statement Monochromatic light of wavelength 592 nm from a distant source passes through a slit that is 0.0290 mm wide. In the resulting diffraction pattern, the intensity at the center of the central maximum (θ = 0∘) is 3.00×10−5 W/m2 . What is the intensity at a point on the screen...
  19. G

    New Near Point with Corrective Lens?

    Homework Statement So I've calculated the person's corrective lens to need the power of -2.00D now I must find the new near point with the corrective lens on. The initial near point is 15cm and I converted the -2.00D into cm, which is -50cm (I hope). Homework Equations I've used this formula...
  20. Vitani11

    What is the magnetic field at point P?

    Homework Statement A closed loop carries a current of 8.0 A in the counterclockwise direction. The radius of the outer arc is 0.6m and that of the inner arc is 0.40m. What is the magnetic field at P? Homework Equations F = ILxB F = qV x B R = outer radius r = inner radius The Attempt at a...
  21. M

    Min. distance from a point to a line in 3d

    Homework Statement There's a person on the ground in (0,0,0). An object comes from the sky and hits the ground at (a,b,0), but continues propagating, that is, it does not stop. I need to find the minimum distance between the person and the object. All we know is that the person is in (0,0,0)...
  22. N

    MHB Find xf^7(x)''(0): Chain Rule Explanation

    Assume we known that f(0) = 1 and f'(0)=2 Find xf^7(x)''(0) Will chain rule work here? is the u=xf^7 and y = u^7 I don't know if I am going in the right direction.
  23. Kernul

    Equation of line parallel to another passing through a point

    Homework Statement Write the parametric and cartesian equations of the line passing through ##P = (-\frac{3}{10}, 0, \frac{1}{10})## and parallel to $$r : \begin{cases} 10x + 4y - 3 = 0 \\ x + z = 0 \end{cases}$$ Homework EquationsThe Attempt at a Solution Since the two lines have to be...
  24. NihalRi

    Two point charges and electric potential difference

    Homework Statement In an experiment modeling point charges I had to find equipotential lines. I did so using a voltmeter. The results looked like this: Not a good quality picture, but the equipotential line on the right says 1.3 mV and the one on the left says 2.3mV. From this I had to...
  25. PhanicKnight

    [College Physics] Electric field and point charge

    Homework Statement Around a point charge there are three points: A, B and C. Determine the electric field vector for those points. Also, determine the force vector for q0 if it was in point B. Q = 10 µC, a = 1 m, b = sqrt(3) m, q0 = 10 pC 2. The attempt at a solution Here is the attempt at a...
  26. F

    Shear stress at centroid vs other point

    [ Mod Note: moving this to Physics H/W ] Homework Statement for this question , I'm having problem with the shear stress at point E and shear stress at centorid. normally , the shear stress at the centoid will be maximum . But , in my working , I found that the shear stress at the centroid is...
  27. F

    Shear stress at particular point in beam

    Homework Statement In the example , I suspect the selected A (area) is wrong... From the notes , A' is the area of top (or bottom ) portion of the member cross sectional area . But , in the example , we could see that the selected area is located to the right of the point where shear stress is...
  28. Rod Alexei

    Point charge between two parallel plates (capacitor)

    1. Homework Statement A fixed parallel plate capacitor is charged. A point charge is starting to move with an initial speed 1.0 m/s at shown initial position. The capacitance is 5.0 F. The mass of the point charge is 0.80 kg. Assume that the plate length is infinite. No gravity. The initial...
  29. A

    How far from the starting point do the pieces fall on ground

    Homework Statement An object is thrown with speed 20 m/Sunder the angle pi/3 rad with the horisontal direction. In the highest point, the object is divised into two pieces with same weights. One of them, after the division has the speed 0. How far from the starting point do the pieces fall on...
  30. VMP

    Point mass rotating about a pole with a spring

    Homework Statement In the beginning a point mass is rotating in a circle of radius L. The spring is providing the centripetal force (\vec{F}=-k\vec{r}) and the mass rotates with constant speed. At some point in time, a stick of radius a (a<<L)lands near the center of the circle in such a way...
  31. terryds

    Wave Problem (time for a point to move half a wavelength)

    Homework Statement If a wave y(x, t) = (6.0 mm) sin(kx + (600 rad/s)t + θ) travels along a string, how much time does any given point on the string take to move between displacements y=+2.0 mm and y=-2.0 mm? Homework Equations ω=2πf (but it's not necessary in this problem, this problem just...
  32. I

    Proving that three closed orbits must contain a fixed point

    A smooth vector field on the phase plane is known to have exactly three closed orbit. Two of the cycles, C1 and C2 lie inside the third cycle C3. However C1 does not lie inside C2, nor vice-versa. What is the configuration of the orbits? Show that there must be at least one fixed point bounded...
  33. T

    MHB Find the Slope of a Curve y=f(x) at (a,f(a)) - Determine a f

    The limit below represents the slope of a curve y=​f(x) at the point​ (a,f(a)). Determine a​ f After finding the f(x) and a, I did this:8(3^2+3h(3)+3h(3)+h^2)-72 dividing by h getting h(8h^2+144) dividing by h; canceling the h's and the plugging in the limit h --> 0 getting 144. But I am...
  34. P

    Understanding Far Points and Lens Power in Correcting Myopia

    Homework Statement While carrying contact lenses of D=-2.00 diopters, a nearsighted person takes a vision test and finds that his/her far point is 10.0m a) what is the person's far point without contact lenses? b) what lens power is required to correct the myopia fully? Homework Equations 1/f...
  35. C

    Adjustment in levelling for same point vs unknown point

    Homework Statement in photo 391 , we can see that the levelling work is back to the same point , which is TBM1 . so , the adjustment of correction is (Bs -Fs ) / number of points ... But in 392-394 , the levelling work is from a known point to a different point ... I'm wondering that is the...
  36. S

    Esters' high boiling point

    Why does 3-methylbutyl ethanoate have a higher boiling point than 3-methylbutan-1-ol and ethanoic acid? Attempt at a solution: I know that the ester has a marginally greater molar mass but I wasn't sure if this is the only deciding factor, particularly considering the strength of the other...
  37. evinda

    MHB Find the function at the point (0,0)

    Hello! (Wave) Let $v(x,y)$ be a harmonic function in $\mathbb{R}^2$. I want to compute $v(0,0)$ given that $v|_{x^2+y^2=1}=\sin{\phi}+1$, where $x= \cos{\phi}, y=\sin{\phi}, \phi \in [0,2 \pi)$. I I thought that we could use the following theorem. $(\star) \Delta u=0 \text{ in } B_R(0)...
  38. toforfiltum

    Newton's method to approximate critical point

    Homework Statement Let ##F(x,y)=4sin(xy)+x^3+y^3## Use Newton's method to approximate the critical point that lies near ##(x,y)=(-1,-1)## Homework EquationsThe Attempt at a Solution I have a problem here because the derivative is not a square matrix. Hence, I can't find the inverse needed for...
  39. Drakkith

    Slope of a Line Tangent to a Level Curve at a Point

    Homework Statement The equation ## f(x,y) = f(a,b) ## defines a level curve through a point ## (a,b) ## where ## \nabla f(a,b) \neq \vec 0##. Use implicit differentiation and the chain rule to show that the slope of the line tangent to this curve at the point ##(a,b)## is ##-f_x(a,b)/f_y(a,b)##...
  40. N

    I How does a Point Force Affect a Piezoelectric?

    So, let's imagine we have a sphere of metal with a piezoelectric film all around the outside of it. If we applied a point force to one area of the sphere, how would the piezoelectric material react? Would it compress or expand at that point, and how can we measure the force based on the response...
  41. R

    Moment about a point in an incline plane

    Homework Statement Force F = 460 N acts perpendicular to the inclined plane Determine the moment produced by F about point A. Enter the x, y, and z components of the moment separated by commas. Homework EquationsThe Attempt at a Solution r(CA)=4j-3k u(CA)=4/5j-3/5k r(CB)=-3i+4j...
  42. Bishamonten

    Finding the point on the line of intersection between planes

    Homework Statement Given two planes, P1, P2. Find parametric equations for the line of intersection between the two planes. Homework Equations P1 = 2x -3y + 4z = 3 P2 = x + 4y - 2z = 7 The Attempt at a Solution Let N1 be the normal vector to P1, and N2 be the normal vector to P2. Then, N1...
  43. Pallatinus

    Show that the gradient is perpendicular to a point

    Homework Statement ##W = x^2+5y^2## Show that ##\nabla W## is perpendicular to the level curves of W at ##(X_0, 0)## Homework Equations ##\nabla f(x,y) = <\frac {\partial f} {\partial x} , \frac {\partial f} {\partial y}>## The Attempt at a Solution I know that the gradient is always...
  44. D

    Melting point and boiling point

    Why there is huge difference in M.P. and B.P. Of Oxygen (M.P. - 54K,B.P.- 90K) and sulphur (M.P. - 393 K, B.P. - 718 K)
  45. toforfiltum

    Approximating equation for tangent plane at a point

    Homework Statement Suppose that you have the following information concerning a differentiable function ##f##: ##f(2,3)=12##, ##\space## ##f(1.98,3)=12.1##, ##\space## ##f(2,3.01)=12.2## a) Give an approximate equation for the plane tangent to the graph of ##f## at ##(2,3,12)##. b) Use the...
  46. R

    Moment about a point of a hammer

    Homework Statement In order to pull out the nail at B, the force F exerted on the handle of the hammer must produce a clockwise moment of 590 lb⋅in about point A.(Figure 1) Determine the required magnitude of force F. Homework EquationsThe Attempt at a Solution M=590lb*in -590=...
  47. R

    Moment about a point of a crane

    Homework Statement The towline exerts a force of P = 5.8 kN at the end of the 8-m-long crane boom. If θ = 30∘ determine the placement x of the hook at B so that this force creates a maximum moment about point O. Homework EquationsThe Attempt at a Solution M(max)= 8(5800) = 4.64kN*m My...
  48. A

    Finding the point of equilibrium

    Homework Statement As a stunt coordinator with a background in physics, you have been asked to determine whether Man can make it across the river and whether the rope will hold his weight. Man is rather small, with a mass of only about 48.7 kg, including his equipment. The crossing distance is...
  49. Vanessa Avila

    Statics: Finding the moment on point B?

    Homework Statement [/B] Determine the moment about point B of each of the three forces acting on the beam. Homework Equations M = F*d⊥ The Attempt at a Solution I went and found the components for each of the forces. Please double check it if I did them right: F1 : Fx = 0 Fy = 375 lb F2: Fx...
  50. moenste

    Point between two wires at which the flux density is zero

    Homework Statement A long wire (X) carrying a current of 30 A is placed parallel to, and 3.0 cm away from, a similar wire (Y) carrying a current of 6.0 A. What is the flux density midway between the wires: (a) when the currents are in the same direction, (b) when they are in opposite...
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