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. Jozefina Gramatikova

    Find the tangent plane given at the stationary point.

    Homework Statement Homework Equations [/B]The Attempt at a Solution I got -1, but the answer says "6". Could you help me, please?
  2. Pratik Saha

    Gravitational Potential Reference Point

    Can someone please show that calculation of gravitational potential energy at a point R+h from the centre of the Earth by choosing the centre of the Earth to be at zero potential. Here R is the radius of the Earth and h is not very small wrt to R
  3. M

    Automotive Flash Point of Petrol & Diesel: Pressure & Self Ignition

    Flash point temperature of petrol is lesser than that of diesel at the same pressure. Does this mean, if I take petrol and diesel as liquids in separate containers and heat them, rapid vapourisation (rapid enough to sustain a combustion) of petrol occurs at a lower temperature(fire point) than...
  4. lordlarddallas

    Potetial Difference between center and point r

    Homework Statement A cylindrical conductor of length L and radius R, L » R, carries a charge Q. 1. Neglecting boundary effects; evaluate the potential difference between a point at distance r from the center of the cylinder, and the center. Assume r to be of the same order of magnitude as R but...
  5. R

    I Rayleigh distribution and the probability of a point

    Okay, so I just found out about the Rayleigh distribution being the radial distribution of a point composed of normal distributed cartesian components. And this is because of the area element, right? But how then can the joint density of the cartesian component's distributions equal that of the...
  6. Krushnaraj Pandya

    Analyzing a circuit with 1 point earthed

    Homework Statement Find potential of A and B in the given figure. (pardon poor quality, I only have a webcam) Homework Equations All related The Attempt at a Solution marking 1 to 4 from left to right. C1,C2,C3 are in series. C123=(2/3)C. which is in parallel with C4. C effective is 5C/3...
  7. T

    Question about the point slope formula

    Homework Statement What is another form of point slope formula Homework Equations Y = mx+b The Attempt at a Solution Y - y2 = m(x - x2) I’m not sure I’m trying to find B but I don’t know how
  8. M

    Difference between flash point, fire point and self ignition temperatures

    Is there any difference between setting petrol on fire directly(by contacting it with burning stick) and heating petrol in a vessel, increasing its temperature above itself ignition temperature and making it burn spontaneously? What is the difference between flash point,fire point and self...
  9. NatFex

    I Rotation of a point in R3 about the y-axis

    Hello, I'm having a visualisation problem. I have a point in R3 that I want to rotate about the ##y##-axis anticlockwise (assuming a right-handed cartesian coordinate system.) I know that the change to the point's ##x## and ##z## coordinates can be described as follows: $$z =...
  10. D

    Should point at which E field = 0 coincide with V = 0?

    A problem I solved asks this: There is a point charge of 3q at the origin and another charge of -2q at x = 5. At what value of x relative to the origin is the electric field equal to zero? So: E = E1 + E2 0 = E1 + E2 E1 = -E2 kQ1/x2 = -kQ2/(5-x)2 Solving for x, the point at which these...
  11. T

    Distance of a point from a compact set in ##\Bbb{R}##

    Homework Statement Let ##K\neq\emptyset## be a compact set in ##\Bbb{R}## and let ##c\in\Bbb{R}##. Then ##\exists a\in K## such that ##\vert c-a\vert=\inf\{\vert c-x\vert : x\in K\}##. 2. Relevant results Any set ##K## is compact in ##\Bbb{R}## if and only if every sequence in ##K## has a...
  12. K

    I Uniqueness of tangent space at a point

    How do you show that there can be only one tangent space at a given point of a manifold? Geometrically it's pretty obvious in 3 dimensions, as one notices that there can be only one tangent plane at a point. But how could we show that using equations?
  13. José Ricardo

    Boiling point and connection distance of the elements

    Homework Statement Explain the following order of the boiling point (° C) HF (19.5)> HCl (-85.1) <HBr (-66.8) <HI (-35.4) b) Explain the following order of connection distance (pm): HF (92) <HCl (127) <HBr (141) <HI (161) Homework Equations xxx The Attempt at a Solution a) HF does hydrogen...
  14. E

    B The correlation between a dimensionless point and a line

    I see no correlation between a dimensionless point and a line although it appears that math has made one. I'm just a philosopher so it's quite possible that I've got it all wrong. It seems as though any location along a line is always the same location. If a location has no size then it can't...
  15. Decimal

    Relation between temperature and boiling point?

    Hello, I am encountering some confusion with the relation between the latent heat of vaporization and the temperature of a substance. I understand both the latent heat and the entropy change of vaporization are dependent on the temperature, assuming the pressure is held constant. However given...
  16. CDL

    Point Charges on a Polygon with another Charge in the Middle

    Homework Statement Suppose we have a regular n-gon with identical charges at each vertex. What force would a charge ##Q## at the centre feel? What would the force on the charge ##Q## be if one of the charges at the vertices were removed? [/B]Homework Equations Principle of Superposition, the...
  17. CristianHernandez

    How to concentrate white light in a very small point?

    Good morning everyone. I have a question for the community. I am doing an optical project in which I need, as the title says, to concentrate white light in a very small point, with a diameter of the order of microns, so that I can pass light through a pinhole. I've been trying it with some lens...
  18. B

    I Probability of a random walk reaching the point X; maximal c

    https://ibb.co/guBuPd As the title indicates, I want to calculate the Probability of a stock price reaching a determined point, by considering the system as a random walk model, and after that, to compute the so called "maximal curves". I found the whole explanation in this article...
  19. isukatphysics69

    Find the equation of a tangent line at each given point

    Homework Statement in title Homework Equations x=2cotθ y=2sin2θ dy/dx = 2sin3θcosθ y-y1=m(x-x1) point = (-2/√3,(3/2) The Attempt at a Solution Have been stuck for hours I solved for the dy/dx above, now I need to figure out how to get rid of the θ to get my equation in terms of x so I was...
  20. K

    I Determining Plate direction by having three point of it.

    Hi all, Can anyone help to solve this problem? Imagine a big plate suspended in the air through three threads with different length. we know length of each individual thread, and they are 120 degree apart from each other. How cam we calculate the tilt of the plate and direction of the tilt?
  21. K

    A Symmetries of a Diamond Unit Cell - Point Group Confusion

    Dear All, I've been recently reading the very clear text of Burns and Glazer entitled Space Groups for Solid State Scientists in the context of my thesis which requires understanding of symmetries of crystals, more specifically symmetries of (approximate triply periodic minimal surfaces)...
  22. S

    Why are 3 planes needed to define stress at a point?

    My question is simple. Why do we need 9 different quantities, ie 1 normal stress and 2 shear stresses on 3 different planes, to define stress at a point? example: http://www.geosci.usyd.edu.au/users/prey/Teaching/Geol-3101/Strain/stress.html I think it should be enough to define the 3 stresses...
  23. K

    Finding the minimum pass point

    Homework Statement A factory is hiring ##m## employees. A number ##n > m## of candidates applied to the job. They need to answer an exam consisting of questions all of equal weight. A candidate is selected to the next step (the interview) if he/she achieves a minimum of ##c## points in the...
  24. F

    Find the magnetic field at a point

    Homework Statement Homework Equations B=(μ0*I)/(2πr) The Attempt at a Solution B2 = (4*4*10-7)/(2*0.1) = 8 μT B1 = (3*4*10-7)/(2*0.1) = 6μT Could I know how to determine the directions ?
  25. ubergewehr273

    Problem in electrostatics: E-field near 2 point charges

    Homework Statement Refer the image. Homework Equations kq1q2/r^2 = F Potential energy = kq1q1/r The Attempt at a Solution Obviously since both charges are unequal in magnitude option a is incorrect. Calculating field at large distance r, E = kq1/r^2 - kq2/r^2 = kq2/r^2 Also potential energy...
  26. C

    I Analysis of Ultrasonic Waves at a point

    I have a question regarding a theoretical analysis of Ultrasonic waves : The next picture represents a system of transducers sitting on fixed boards: Datum: * there are 4 transducers ( represented by blue color , indexed by letter ' T ' ) , each outputting Ultrasonic wave (represented by...
  27. TheQuestionGuy14

    B What is the GZK Cut Off Point and why does it happen?

    What is the GZK Cut Off point? I've seen an article stating that Prof. Silas Beane says a sort of 'lattice', an energy limit, which may suggest we are living in a matrix. But that can't be right? Can it? What actually causes it and why does it happen?
  28. R

    Where is the hinge point? & what is the moment of inertia of a square?

    Homework Statement :[/B] A uniform wire of linear mass density λ having three sides each of length 2a is kept on a smooth horizontal surface. An impulse J is applied at one end as shown in the figure. P is the midpoint of AB. Now answer the following questions. 1) The angular velocity of system...
  29. L

    Express E due to a point charge at the origin

    Homework Statement Express the electric field E due to a point charge q at the origin in cylindrical polar coordinates. Homework EquationsThe Attempt at a Solution Know that E = q / 4*pi*epsilon_0*r^2 in the r-direction, which is the answer in spherical coordinates. How we we swap to cylindrical?
  30. isukatphysics69

    Using potential energy graph, find particle turning point

    Homework Statement Homework Equations Emec - PE = KE The Attempt at a Solution When particle starts at x = 4 KE = .5(.25)(225) = 28.125 Energy of system = 28.125 I don't have anything with position here so i am unsure how to find what position that the energy will be equal to the Emec and...
  31. J

    Motion of point when sound volume goes up

    Homework Statement A radio speaker produces sound when a membrane called a diaphragm vibrates, as shown above. A person turns up the volume on the radio. Which of the following aspects of the motion of a point on the diaphragm must increase? a) the max. displacement only b) the average...
  32. J

    Point charge - Assertion & Reason type problem

    Homework Statement Homework EquationsThe Attempt at a Solution These AR type problems are mostly tricky and debatable . To me, A is correct and R is wrong . Although electron is approximated to be a point particle , but I think if R is true , then A will be wrong . I think c) is correct ...
  33. O

    Find the distance from the point P to a line - linear algebra

    Homework Statement Find the distance from point P (1,7,3) to the line (x,y,z) = (-2,1,4) + s(1,-3,4), s is a free variable Homework Equations projnQP = ( QP⋅n/(lengthQP)(lengthn) )(n) The Attempt at a Solution I'm not quite sure about how to find the normal (n) here, but if I make s=0, I'm...
  34. maistral

    Cubic equation of state near critical point (~0.95 < Tr < 1)

    Hi. I have read somewhere that cubic equations of state seem to have convergence issues when vapor pressure calculations are done near the critical point. Sadly, I have forgotten where I have have read it :( I would like to ask some knowledgeable people regarding this, or can people point me I...
  35. A

    Finding the New Acceleration Given Point Charges

    Homework Statement A point charge q1=15.00μC is held fixed in space. From a horizontal distance of 8.00 cm , a small sphere with mass 4.00×10−3kg and charge q2=+2.00μC is fired toward the fixed charge with an initial speed of 40.0 m/s . Gravity can be neglected. What is the acceleration of the...
  36. quasarLie

    I Relation between the Point Spread Function (PSF) and the Morphological Index

    Hi, I want to know the relation between the point spread function (PSF) and the morphological index (Sharp, Sround, Ground). what does the PSF represent? and what is it's importance in the detection of astrophysical objects (quasars, galaxies)? Thanks
  37. F

    Stagnation point and a water dam

    Hello Forum, I am clear on what the pressure at a point ##P## is on the wall of heigh of a dam at a certain depth ##d## below the water free surface: ## \rho g d+P_atm##. The deeper we go the higher the pressure. Now let's consider a different scenario: there is initially no water and water...
  38. Livio Arshavin Leiva

    A What exactly is a "rare event"? (Poisson point process)

    These days I've been reading in the internet about the Poisson Distribution because that was a concept I couldn't manage to understand completely when I studied it, so since then I've been always quite curious about Poisson processes, and how there are a lot of natural phenomena (mostly the...
  39. Clara Chung

    Vector problem: distance between a point and a line

    Homework Statement Homework EquationsThe Attempt at a Solution My answer is d = |(a-b)x(p-b)|/|(b-a|). I first find out the area of the parallelogram produced by BA and BP and divide the area by length AB to get the height. Why am I wrong?
  40. E

    Finding the electric field at point - Can someone check my work?

    Homework Statement Four equivalent charges are placed at (0,0), (a,0), (0,a), and (a,a). What is the electric field at point B (a, a/2)? Homework EquationsThe Attempt at a Solution My attempt: Charges at (a,a) and (a,0) cancel each other out. E_{(0,a)}= \frac{Q(\hat{x}a...
  41. F

    Find the electric field at a point away from the charged cylinder's axis

    Homework Statement Homework Equations ##E=\frac{kQ}{r^2}## 3. The Attempt at a Solution ##Q_{enclosed} = 0 ## , because there is no charge inside the conducting cylinder. E = 0 Can anyone check my answer please ?
  42. K

    Direction of the Magnetic Field at a Point

    Homework Statement The problem asks to find the direction of the magnetic field at point P, which is at the center of 2 separate semi-circle wires that form a circle. The current in each wire flows in the same direction (to the right). I attached a picture below. Homework EquationsThe Attempt...
  43. Monoxdifly

    MHB Finding the Distance from Point P to AC on an ABCD.EFGH Cube

    Given an ABCD.EFGH cube whose its side length is 8 cm. The point P is within AB so that AP = 3PH. The distance between P to AC is ... A. 2\sqrt3 cm B. 3\sqrt3 cm C. 2\sqrt6 cm D. 3\sqrt6 cm E. 4\sqrt6 cm So AH is 8\sqrt2 cm and PH = 6\sqrt2. What do I do now? Is the triangle HPC a right triangle?
  44. F

    Find the electric field of a point P at a distance r

    Homework Statement Homework Equations The Attempt at a Solution Can anyone check my answer please ?
  45. C

    How to work out the reflection point of waves

    Homework Statement When a workman strikes a steel pipeline with a hammer, he generates both longitudinal and transverse waves. The two types of reflected waves return 2.4 s apart. How far away is the reflection point? (For steel, vL = 6.2 km/s, vT = 3.2 km/s). Homework Equations Unknown...
  46. Sunanda

    Electric Potential due to a single point charge

    Please refer to the image attached. So, my doubt is: While calculating dW in the derivation, we know this work is being done by external force, because only then the unit positive charge can be made to move towards the charge +Q. So dW should be equal to Fext.dx but here in the book it is shown...
  47. A

    How close will body approach fixed point charge?

    Homework Statement Charged sphere with a mass of 15 mg and charge 2 nC moves with a speed of 15 cm/s towards a fixed point charge of 3 nC. How close will sphere approach charge? Homework Equations K=(1/2)*mv2 U=k*(Q1Q2/r) The Attempt at a Solution So I am not sure I approached correctly but...
  48. Z

    Why is the boiling point of 2-propanol lower than 1-propanol

    Homework Statement Why is the boiling point of 2-propanol lower than 1-propanol? The Attempt at a Solution Is this right? Because 2-propanol has its hydroxyl group in the middle of the atom, the electrons are all moving to the centre of the atom as opposed to 1-propanol, which has the...
  49. H

    MHB Probability of winning a point on serve in tennis

    Hello, my question about calculating the probability in tennis I know that to calculate Pwos (probability of point won on oun serve ) for each player the following formula is used... # P(no Fault) -The probability a player's first serve not faulting # P(win/no Fault) -The probability a player...
  50. Shadow89

    I In a rifle scope, why is the reticle at the focal point?

    In order for a conventional telescopic riflescope to function, it must invert the image two times. As a result, the light-rays traveling through the tube must meet at two focal points. With my limited knowledge of optics, i assume that parallell light going in through the objective will meet...
Back
Top