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."

View More On Wikipedia.org
Recent contents Top users
  1. F

    Yield Point: Why Can Material Elongate without Force?

    Homework Statement I was told that yield point is a point which the material which will have an appreciable elongation of yielding without any increase in load . my question is If there's no increase load , how can the material elongate ? Homework EquationsThe Attempt at a Solution IMO ...
  2. R

    Equivalent force couple systems at a point on a rigid body

    Homework Statement Attached is a pdf of the assignment problems, I'm looking at problem 1 under the "Try" section. It shows a rod attached to a wall bracket on the left, with a force applied on the right side. I'm also including a link to the solution, it's under "Problem 3.83" -...
  3. L

    A Saddle point Integrals with logarithm and cosine

    I'm trying to use the saddle point method to solve the following integral: Z = (1/sqrt{2 pi t}) ∫_{1}^{infinity} ds (1/sqrt{2 pi s}) exp{ p [-s ln(s/t) +s] } cos(2 pi L~ p ~ s), as p → infinity Mod edit to make integral more readable: $$Z = \frac{1}{\sqrt{2\pi t}} \int_1^{\infty} \frac 1...
  4. JesseJC

    Counting floating point operations in an algorithm

    Hey guys, another question regarding MatLab here. In this assignment, I need to create a function of 'k' to count the number of floating point operations in the algorithm that I've made. Here is my code so far: expAk = zeros(1000, 1000); load('CA3matrix.mat'); times = zeros(15, 1); for j =...
  5. Ravi Singh choudhary

    Reliability of Upper/lower yield point in tensile test.

    Some metal give two yield point in stress strain diagram. One is called Upper yield point and Lower yield point. Why lower yield point is considered as more reliable. I can think of Upper yield point is much more dependent upon experimental apparatus settings. So why lower yield point is much...
  6. R

    Calculating Smallest Path Length Difference for Overlapping Waves at Nodal Point

    Homework Statement Two point sources, S1 and S2, are vibrating in phase and produce waves with a wavelength of 2.5 m. The two waves overlap at a nodal point. Calculate the smallest corresponding difference in path length for this point. Homework EquationsThe Attempt at a Solution I really...
  7. A

    How Does Closing a Valve Affect Flow Rates in Multi-Suction Pipe Systems?

    If I a pump with a main suction header and 4 smaller branch connections of difference sizes. Let's say for this example we have (2) 3", (1) 1", and (1) 2". Also let's say our pump is requiring 20 gal/min. The flow rate of each branch would be proportional to the area of the pipe correct? flow =...
  8. M

    Deriving perfect fluid energy tensor from point particles

    Homework Statement For a system of discrete point particles the energy momentum takes the form T_{\mu \nu} = \sum_a \frac{p_\mu^{(a)}p_\nu^{(a)}}{p^{0(a)}} \delta^{(3)}(\vec{x}-\vec{x}^{(a)}), where the index a labels the different particles. Show that, for a dense collection of particles...
  9. R

    Gravitational force - point mass and circular platform

    Homework Statement Calculate the gravitational force between a point mass and a circular platform. Homework Equations G=m1*m2/r^2 The Attempt at a Solution http://i.imgur.com/dfZf9GK.jpg The actual solution is different. They integrated by the angle between a/r (alpha) but i do not...
  10. D

    Point Transformations in the Lagrangian

    Homework Statement Hi, I'm working on understanding how a time independent point transformation . effects the Lagrangian and to see how what values are co and contra variant.Homework Equations Would these be correct formulations, or have I overlooked something? The Attempt at a Solution and...
  11. D

    B Understanding Point Mass: An Example

    What does it mean to treat something as a point mass. Give an example as well. Thank you.
  12. Destroxia

    Where are the extrema and inflection points for the function y = x/ln(x)?

    Homework Statement Find all extrema and inflection points of the function ## y = \frac {x} {ln(x)} ## Homework Equations I did the first and second derivative by hand, and they worked out in CAS as well... ## y = \frac {x} {ln(x)} ## ## y' = \frac {lnx - 1} {(ln(x))^2} ## ## y'' = \frac {2...
  13. C

    How Does Vapour Pressure Change at Dew Point for Benzene-Toluene Mixtures?

    THERE IS NO TEMPLATE BECAUSE GHIS HOMEWORK WAS PLACED IN AN INCORRECT FORUM Equimolar benzene and and toluene form essentially ideal solutions. At 20degC the vapour of benzene and toluene are 9.866kPa and 2.933kPa respectively. The solution is boiled by reducing the external pressure below the...
  14. 1

    Why does the point experience NEGATIVE field strength?

    Hi, i'm looking for an explanation to this answer of a past paper that I'm doing, it's from OCR (A level) G485, question 1 b ii) the question on top, and answer on bottom i don't understand why would the point experience a negative electric field strength when it's getting closer to a...
  15. SSGD

    Light Momentum Transfer between point charges

    Hi, I am trying to understand how light momentum transfers between point charges. I have a few questions if you could help me find some answers or direct me to some sources. Situation #1 Electron/Wire - There is an electron at rest light years away from a wire that has AC flowing thru it...
  16. M

    Deriving perfect fluid energy tensor from point particles

    Homework Statement [ For a system of discrete point particles the energy momentum takes the form T_{\mu \nu} = \sum_a \frac{p_\mu^{(a)}p_\nu^{(a)}}{p^{0(a)}} \delta^{(3)}(\vec{x}-\vec{x}^{(a)}), where the index a labels the different particles. Show that, for a dense collection of particles...
  17. P

    Order of branch point of z^(-1/2)

    Homework Statement Give the location and orders of the branch points at, and classify the singularities f(z) =\frac{1}{z^{1/2}} Mod note: Fixed LaTeX in exponent above and below. To OP: To write a fractional exponent such as ##z^{1/2}## use braces around the exponent, like this: ##z^{1/2}##. It...
  18. Blockade

    How can I find the inertia of a rod with a pivot point?

    I have a question on finding the inertia of a rod with a pivot point somewhere along it's length. So the inertia of a rod is IStick cm = 1/12 *m*L2 Does L2 = (2L/3)2 = 4L2/9 -> 1/12 *m*[4L2/9] or is it something like m*L2/12 + m* (2L/3)2? If it's the second one then may I ask why it's that...
  19. JulienB

    Mass point sliding on a rotating line (Lagrangian)

    Homework Statement Hi everybody! I have a crazy problem about Lagrangian on which I've been working on for two days without being able to figure it out. I have a solution, but I think there is a flaw in it. First here is the problem: A line rotates with constant angle velocity ##\omega##...
  20. C

    Electric field strength at a point between charges

    Homework Statement A +1.0 μC charge is placed at point X. A +4.0 μC charge is placed at point Y, 50 cm from X. How far from X, on the line XY, is the point where the electric field strength is zero? Homework Equations E = Q/4πε0r2 The Attempt at a Solution I know that the electric field is...
  21. Z

    The distance between the incident point and the refracted point

    Homework Statement http://s32.postimg.org/4urcaq0xx/image.png The incidence angle of a light ray over a tile of glass with dy faces parallel is pi/3 rad. Find the distance between the incidence point and the refraction one of the ray with the tile, if the distance between these rays is 0.7 cm...
  22. K

    Do # of magnets affect the time for a metal"s Curie point?

    I'm doing an experiment regarding Nickel's time for a Curie point. The nickel will be connected to a wire on a pendulum and will be attracted to a neodymium magnet, but it will not be touching it. A candle will be placed in front of the magnet so that when the nickel moves toward the magnet as...
  23. Tony Stark

    Equivalence point in acid-base titration

    In acid base titration, we try to neutralize the analyte by adding sufficient titrant and observing the color change in the indicator. But if the analyte is neutralized, then it must always be at ph 7. Why is it that we use indicator of different ranges to check equivalence point?
  24. prashant singh

    Question related to nine point centre

    1. Prove that nine point centre is the mid point of orthocentre and circumcentre.Homework Equations3. I know about euler line and its proof that centeroid,circumcentre and orthocentre are collinear and centeroid divides orthocentre and circumcentre in the ratio 2:1
  25. N

    Why does the polarization point inwards for this problem?

    Homework Statement Griffiths 4.15: A thick spherical shell of inner radius a and outer radius b is made up of dielectric material with a frozen in polarization. P = k / r in the r-hat direction. There is no free charge (why?). Find the electric field inside and out. Homework EquationsThe...
  26. Biker

    I Understanding Boiling Point Elevation: Real Gas Law and Its Impact on Molecules

    So was thinking a little bit about the ideal gas law. ##P V = n R T## And I read an article about the real gas law where they just edited few properties. ##(P + \frac{n^2 a}{v^2}) (V - nb) = n R T ## Where a and b are constant determined experimentally. So going back to our original point, Why...
  27. Adeel Ahmad

    Electric Field, Potential, and Work at a Point

    Homework Statement Homework Equations E = kq/r2 V = -∫ E ⋅ ds W = -Vq The Attempt at a Solution a) I just summed up the electric fields: +ek/a2 +ek/a2 -ek/a2 so I get +ek/a2 as a result. Not sure if this is correct since -e has a y component so I was thinking to use sin but not sure which...
  28. S

    Concave mirror: Reflected rays do not meet at one point

    I have drawn a diagram of the incident and reflected rays of an object by the concave mirror. Red color shows the incident rays, black color shows the normals drawn from the center of curvature, while green color shows the reflected rays. Shouldn't all the reflected rays meet at one point. Any...
  29. A

    MHB Margin of error and point estimate together

    Hey all I have one last question for you. I just need clarification on point estimate and margin of error as I have to find both in a problem. Let's say the endpoints are 5.9 and 8.1. When I do a margin of error problem, I subtract the mean of 7 from 8.1 right? When I do point estimate do I add...
  30. O

    Pure rotation under a point force and a distributed friction

    Hi guys, I was wondering if it is possible to have a pure planar rotation of a rectangular-prism shaped rigid body on a planar surface when it is subjected to a planar point force at the tip. Is there any range for the point force such that it can not break the static friction force (so no...
  31. SmritiB

    Resistive network point to point analysis

    In a complex resistive mesh (grid), 2 points are chosen for applying a voltage source. Now there are many paths the current can take from A to B. And there is an equivalent resistance computed as well. But how to calculate the least resistive path? I.e. The path along which when traversed, the...
  32. J

    How to find the forces acting on the pivot point ?

    Homework Statement pivot point located at the middle of ramp( Point C). F1=250 lbs @ 12 in from point A F2=250 lbs @ 84 in from point A L=192 in angle from the ground is 25 degrees Homework Equations sum of moments equal to 0 sum of forces equal to to 0 The Attempt at a Solution I did sum...
  33. T

    B At what point would we stop seeing a star?

    The universe is expanding and at some point faster than light so once it reaches that point we won't see the light from those stars. I forget what this point is called. If someone happened to be watching a star as it crossed that point would we see it simply blink out or close to that or would...
  34. F

    Find the force a distance from a fixed point

    Homework Statement A person is standing on tiptoe, with the total weight supported by the force on the toe. A mechanical model for the situation is shown, where T is the force in the Achilles tendon and R is the force on the foot due to the tibia. Find the value of T. Assume the total weight is...
  35. N

    Electrostatic potential a a point, the pluses and minuses

    On calculating the electrostatic potential at a point due to charge q, by definition, it is the work done to bring a unit positive charge from infinity to that point. Trying to find it mathematically, it should be ∞→R ∫E.dr...
  36. S

    Rolling without slipping taking the contact point as pivot

    I'm confused about this rolling without (or better with) slipping situation. Suppose to have a disk with initial velocity ##v## and angular velocity ##\omega##. The motion is to the right but the angular velocity is counterclockwise. There are no forces acting on the disk besides the kinetic...
  37. P

    Finding an electric field at a point from a line of charge

    Homework Statement A thin insulating rod with charge density lambda=+5nC/m is arranged inside a thin conducting cylindrical shell of radius r =3 cm. The rod and the shell are on the same axis, and infinite in length. What is electric field at point p? 6cm from the central axis. Homework...
  38. Nemo1

    MHB Equation of slope of a function that passes thru a point

    Hi Community, I have this following tutorial question and I am stuck. I understand how to take the derivative and find the tangent line at certain value for x Which would say if x=2 and the derivative of \frac{1}{x} equals \frac{-1}{x^{2}} then the slope would be y=\frac{-1}{4}x I am unsure...
  39. R

    Calculating Magnetic Field at a Point Near a Long Wire

    Homework Statement Calculate the magnitude of the magnetic field at a point 100cm from a long, thin conductor carrying a current of 1A. Homework Equations B = ui/2pi(a) The Attempt at a Solution My question is why is this modeled after a problem with an infinite wire? When I first read it I...
  40. S

    Which has the highest boiling point?

    Homework Statement Which one of these had the highest boiling point? A. 3-Pentanone B. 1-Butanol C. Butanal Homework EquationsThe Attempt at a Solution The answer should be 3-pentanone because 1- it's molecular weight is approx 76 compared to the other which has approx 64 2 - because of the...
  41. lep11

    Prove that the critical point of f satisfies the equation

    Homework Statement a.) Let f(x)=(sin x)/x, x≠0. Define f(0) such that f is continuous at x=0. b.) Prove that if x0 is critical point of function f (f(0) defined as in part a), then |f(x0)|=1/(1+x02)-½ (Hint: use the basic properties of sine and cosine with given information.)The Attempt at a...
  42. MidgetDwarf

    Electric Potential Due to point charges

    Homework Statement Two particles each with a charge of +3.00 μC are located on the x axis, with one particle at x = -0.80 m, and the other particle at x = +0.80 m. a) Determine the electric potential on the y-axis at the point y = 0.60 m.b) What is the change in electric potential energy...
  43. H

    Example of torque-free rotation with a fixed point

    What is an example of a rigid body rotating when one point is fixed and there are no net applied torques? And the fixed point is not the center of mass. I considered a cone rolling without slipping on a flat plane is such an example; the apex is the fixed point, but is there a net applied...
  44. M

    How can a point charge exert force on itself?

    An accelerated charge emits radiation and so must lose energy. This implies that it feels a "reaction force" in the direction opposite the motion. Since EM interactions conserve energy/momentum, it must be possible to describe the reaction force in terms of EM fields acting on the charge. These...
  45. P

    Proving that net torque isn't reliant on point of rotation.

    Homework Statement So we have a horizontal bar. Distance = r Forces = F All numbers remain constant with the exception of the distance, denoted as r(set)() Length of bar = 1m F1 = 10N r1-1 = 0m r2-1 = .25m (behind the point of rotation) F2 = 5N r1-2 = 0.5m...
  46. S

    How do I solve systems of equations to find local max, min, and saddle points?

    Homework Statement Find the local max, min, and saddle point for the function: f(x,y) = 2x^2+3xy+4y^2-5x+2yHomework EquationsThe Attempt at a Solution I've taken the two partial derivatives Fx = 4x + 3y - 5 Fy = 3x + 8y + 2 I know that the critical points will sit where both of theses partial...
  47. P

    Motion of a point is equal to dynamic harmonic oscilation

    Homework Statement Point with mass is moving along the positive direction of x axis, its velocity is described by (A-Bx^2)^(1/2). Show that its equation of motion describes dynamic harmonic oscillation and find period (T) of this oscillation. Homework Equations v=(A-Bx^2)^(1/2) A and B is...
  48. S

    MHB Discontinuity: Point discontinuity

    At the very basic level, I understand this notion of discontinuity. But I am looking to understand this better, at a deeper level. Because I know I will need to know this well as I start to explore piece-wise functions. Why do we bother drawing graphs? I want to be able to tell if a function...
  49. F

    B What does the derivative of a function at a point describe?

    I understand that the derivative of a function ##f## at a point ##x=x_{0}## is defined as the limit $$f'(x_{0})=\lim_{\Delta x\rightarrow 0}\frac{f(x_{0}+\Delta x)-f(x_{0})}{\Delta x}$$ where ##\Delta x## is a small change in the argument ##x## as we "move" from ##x=x_{0}## to a neighbouring...
  50. S

    Distance between a point and plane

    Conventionally we have the following equation of a plane ax+by+cz=d where d = ax0+by0+cz0. Where (x0,y0,z0) is a known point on the plane. Now if we try to find the distance between a point P and a plane we take any point on the plane Q (x,y,z) and find the vector from Q to P and project on...
Back
Top