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. E

    MHB Finding the Coordinates of Point D

    Points A ,B and C have coordinates A(1,3) B(5,1) and C(2,-8). point D is such that the vector AD = Vector BC + (2x) vector AB + (3y) vectorAC = vector AB + (2x) vectorAC + (3y) vector BC find coordinates of D
  2. wcjy

    Electric field problem using Gauss' law: Point charge moving near a line charge

    F = qE ma = (2*10^-6) * (λ / (2pi*r*ε0) ) ma = (2*10^-6) * (4*10^-6 / (2pi*4*ε0) ) => I am not certain what to put for r ( But I sub in 4 because dist is 4) a = ( (2*10^-6) * (4*10^-6 / (2pi*4*ε0) ) )/ 0.1 a = 0.35950 v^2 = U^2 + 2 a s v = 0 u^2 = -2 a s => Can't sqrt negative so...
  3. C

    What velocity does the particle need to get to point B?

    It was a long time ago I did these kind of problems so I’m a bit rusty. The only thing I can think of is divide it up to two parts one x and one y. In y the acceleration is sin(a)*9.82? Then put that in the equation and solve for t. In x the there is no acceleration so the formula is x=V0*t, I...
  4. T

    Evaluate the Taylor series and find the error at a given point

    I have the following function $$f^{(0)}\left(x\right)=f\left(x\right)=e^{x}$$ And want to approximate it using Taylor at the point ##\frac{1}{\sqrt e} ## I also want to decide (without calculator)whether the error in the approximation is smaller than ##\frac{1}{25} ## The Taylor polynomial is...
  5. N

    What's the car's acceleration at a specific point?

    I did (0.9-0.1)/(1.5-0.5) = 0.8/1 --> 0.8 m/s^2 This doesn't look right to me. Is this actually correct or do I need to solve the problem a different way?
  6. Hiero

    Magnetic field of a point charge moving uniformly

    Everywhere I look online I see the formula for the magnetic field of a uniformly moving charge is, $$\frac{\mu_0 q \vec v \times \vec r}{4\pi r^3}$$ but when I calculate it by transforming the electrostatic field (taking the motion along x) I get, $$\frac{\gamma \mu_0 q \vec v \times \vec...
  7. Jason234578

    Engineering Moment of a force about point O

    G'day. I have a problem with my statics work, i understand its probably quite simple but I am having trouble in my understanding. Essentially problems make more sense to me by using the component method, although in saying that i understand this problem would be quite a lot more simple were i to...
  8. R

    Using Gauss' Law to find the field at a point

    Attached is problem 23.03 from Halliday and Resnick. We have a sphere of uniform negative charge Q = -16e and radius R = 10cm. at the center of the sphere is a positively charged particle with charge q = +5e. We are supposed to use Gauss' law to find the magnitude of the electric field at...
  9. jaychay

    MHB Find Point D on Plane for 4 Unit Cube Pyramid

    Find point d on the line of r(t)=(0,0,0)+(−1,1,1)t which make the triangular pyramid abcd has the volume of 4 unit cube when a(0,0,0),b(1,0,1),c(0,1,0) are the points on the plane of −x+z=0.
  10. Monoxdifly

    MHB Determining c in Quadratic Function Turning Point

    The graph's turning point of a quadratic function f(x)=ax^2+bx+c is over the X-axis. If the coordinate of the turning point is (p, q) and a > 0, the correct statement is ... A. c is less than zero B. c is more than zero C. q is less than zero D. q equals zero Since the point (p, q) is over the...
  11. J

    Launching a projectile to hit a target moving away from the launch point

  12. docnet

    Calculating Boiling Point of a Solution: A Joke Problem for Extra Credit

    The professor posted a take-home problem for us to solve for extra credit. Extra credit problem: Using nothing but pen, paper and a ham, calculate the boiling point of 1:1:1 solution of benzene, pentane, and ethylene in a pressurized tank filled with neon at 6 atm pressure. The Answer must be...
  13. Hamiltonian

    Total Potential of a Ring at Point P

    I tried finding the potential due to a small element dM of the ring let's say dV, the summation of dV for all the dM's of the ring will give the potential at the point P, but since every element dM of the ring is at a different distance from the point P I am unable to come up with a differential...
  14. S

    What is the significance of using U/2I in four point probe theory?

    Dear Ladys and Gentlemans, I want to measure the sheet resistance R_square on a printed product. My measuring equipment consists a SMU to supply and measure and a four point Probe by Jandel. As output size I get the electrical resistance R (basically the measured Voltage U divided by the supply...
  15. M

    Electric Field of Point Charge at y=r and an Infinitely Long Cylinder

    Let point charge q be at y=r. Let there be an infinite conducting plane along the x-axis and z-axis that is neutrally charged. In this case, the method of mirror charges can be used. The plane is replaced by a point charge -q at y=-r. The electric field for y > 0 is the same in both cases...
  16. tomdodd4598

    I Argument for Existence of Normal Coordinates at a Point

    Hey there, I've been recently been going back over the basics of GR, differential geometry in particular. I was watching one of Susskind's lectures and did not understand the argument made here (26:33 - 35:40). In short, the argument goes as follows (I think): we have some generic metric ##{ g...
  17. LCSphysicist

    Find the vector equation of the line that passes through the point P and intersects with the straight lines R and S

    I think that we can say that PPR = α*PRPS where PR and PS are the points where occurs the intersection on the line R and S. Obs: line r and s are found by knowing that the straight line intersection of two planes are n1 X n2 [cross product] Lr = (0,1,-2) + y(-1,1,1) Ls = (0,1,-1) + u(1,2,1)...
  18. M

    B Critical point of a piecewise function

    If the function is not differentiable at point. Can we consider this point is critical point to the function? f(x) = (x-3)^2 when x>0 = (x+3)^2 when x<0 he asked for critical points in the closed interval -2, 2
  19. G

    Big Data and a Saturation Point

    I ask this with more of a software background than an engineering background, but here I go anyway. Big data is arguably the cultural motif or monograph of the information age. Trends involve immersing ourselves in media of various sorts and processing them at exceptional rates. Of course...
  20. S

    The location of the point with lowest kinetic energy

    I am not sure I understand the question. I imagine there is a horizontal table and all the diagrams are the top-view of the table. The question states that "A particle moves from P1 to P2 without acceleration along five different paths". In the first picture, I think the path is in the shape of...
  21. T

    I Static Point in de Sitter-Schwarzschild Spacetime

    In de Sitter-Schwarzschild spacetime things close to the black hole are falling towards it whereas in greater distance they are receding. So there should be a certain (unstable) ##r##-coordinate, where things are static. The de Sitter-Schwarzschild metric has according to Wikipedia...
  22. P

    B Derivative of a constant scalar field at a point

    Wikipedia defines the derivative of a scalar field, at a point, as the cotangent vector of the field at that point. In particular; The gradient is closely related to the derivative, but it is not itself a derivative: the value of the gradient at a point is a tangent vector – a vector at each...
  23. J

    Comp Sci Least significant bit when there is a radix point (trivial)

    However when there is a binary point where do I start grouping from? Is the rightmost bit considered the least significant bit even then? The other possibility is to begin grouping from the least significant bit for the integral part and then separately begin grouping from the leftmost digit...
  24. B

    Engineering Calculate shear force and bending moments with a UDL and a point load

    Hello, I am looking for some help. I have completed the question below. I will show my answers. My answer: I believe this to be correct. If it is not would appreciate someone letting me know so i can correct. Now i am attempting this question: Could anyone help, or point me in the...
  25. I

    Forces acting on a support point after the system is released

    Summary:: What is the force N which acts on a support point at the moment just after system is released? [Thread moved from the technical forums, so no Homework Template is shown] A light bar with m1 and m2 masses (m1≠m2) at the ends placed on the support point (in the middle of the bar)...
  26. karush

    MHB -apc.3.3.01 Find the equation of the curve that passes through the point (1,2)

    Find the equation of the curve that passes through the point $(1,2)$ and has a slope of $(3+\dfrac{1}{x})y$ at any point $(x,y)$ on the curve. ok this is weird I woild assume the curve would be an parabola and an IVP soluiton...
  27. P

    Calculate the maximum vertical point force P that this beam can sustain

    A simply-supported steel beam with a vertical point force P is shown in Fig. 2(a). A cross-section of the beam, which is composed of two identical C-shaped members bolted back-to-back, is shown in Fig. 2(b). Both C-shaped members have a uniform thickness of 1 cm. Pairs of bolts are located at a...
  28. Saptarshi Sarkar

    Optimization of the distance from the point on an ellipse

    My Attempt :We need to maximize ## D=\sqrt{x^2+(y+2)^2} ## subject to the constraint ##4x^2 + 5y^2 = 20##. From the constraint equation, we can write ##x^2=\frac{20-5y^2}{4}## Using this in the formula for distance, ##D=\sqrt{\frac{20-5y^2}{4}+(y+2)^2}## Differentiating this wrt y, and...
  29. C

    I An interesting point regarding critical points and extrema

    Hi all, I have recently faced some problem about distances between two curves, and (re?)"discovered" an interesting point that I would like to share with you. In the following, we consider a function of two variables ##f(x,y)##, but it should be clear that the definitions and the result is...
  30. K

    Cantilever beam deflection with point mass and point load at the end

    Hi all, I was looking for help with obtaining deflection at end of a cantilever beam with point load at end as well as point mass at the same location. I believe it would be exactly same. Is this correct? That is, I think just adding point mass at the cantilever's end wouldn't change the...
  31. G

    MHB Quadratic equations intersaction point is minimum instead of roots

    I have 2 quadratic functions and I am interested in their root in the specific range. I use quadratic equation to get their roots and what I find that if their any real solution exist for both or any of the function that lie in it designated specific range, then the roots are maximum or minimum...
  32. Tymofei

    Calculating the Moment from a Different Vantage Point

    Summary:: Just a simple 3d rigid dynamics question which I am trying to solve by placing coordinat system differently from original solution.Everything looks ok but results are different. Mod note: Post moved from technical section. Thats my question.As you see coordinate system was located...
  33. N

    Calculating Electric Field for 4 Point Charges in a Square Configuration

    I have the following question and I can't figure out how to, is there anybody who can help?
  34. C

    MHB Find the Bearing from A to C & Angle B: Solve Here

    Dear everyone, An airplane flies 470 miles from point $A$ to point $B$ with a bearing of 25 degrees. It then flies from 250 miles from point $B$ to point $C$ with a bearing of 40 degrees. Find the distance and the bearing from A to point C. Work I understand that I need to use law of...
  35. G

    Potential at a Point: A Question of Solutions

    I thought the right choice was d). But when it comes to the solutions, it is b) and I don't understand why. My reasoning would be: the potential at a point is the work that the electric field does to transport a charge from infinity to that point, so if the field is zero, it does no work and...
  36. ElectronicTeaCup

    Tension T in a parabolic wire at any point

    I am unsure how to go about this. I tried following the suggestion blindly and end up with with some cumbersome terms that are not the answer. From what I understand the derivative at each point would equal to T? Answer: I just can seem to get to this. I think I'm there but can't get it in...
  37. ttpp1124

    Parallel Tangent Line on y=2-e^x+4x and 2x+y=5?

  38. ttpp1124

    Determine the point on the given curve

  39. R

    Determining moment (or torque) around a certain point on a wrench

    Here's a diagram of the problem. There are 3 possible solutions: 163 in-lb clockwise, 163 in-lb counterclockwise, 82.7 clockwise or none of them. After attempting the problem the closest I got to was 82.7 but that was wrong so I'm still stuck.
  40. R

    Calculate the Temperature and Pressure of a melting point

    Adiabatic increase in pressure implies Tds=0, can someone tell me how to proceed?
  41. r-swald

    Find the escape velocity from 2 point charges

    Below is the work I've attempted. I used 2 PE b'c there were 2 point charges, and only one KE b'c only the proton is moving. The final equation in case it's hard to see is V(esc) = sqrt (4kQq / mr). I'm not sure if I did it right. Did I set up this equation right? and I am also not sure what...
  42. P

    Ratio of the Earth's core radius to total radius via seismic turning point

    I've attached a figure I've made; I know I'm to assume the Earth is a perfect sphere in this case. Assuming the 103 degrees is measured as latitude, I've calculated the distance in kilometers (Xp in the second equation above) to be 1.1453e4 km. I know I need u = p at the turning point, but not...
  43. G

    E-field at the origin from two point charges

    Using superposition and "breaking up" the vectors into three components ax, ay, az on points should solve the task. For Q1 there is no effect on x-axis. On the y-axis the distance from Q1 to origin is 2. Using coulombs law will give us -> (-Q/4) * k , where k is the constant 1/(4*pi*e0). On...
  44. Benjamin_harsh

    B What's the exact point about time travel?

    It shows theory of time machine proved, what's the exact point that stopping our scientists to create time machine in reality?
  45. G

    Confusion on the concept of point of rotation

    --no explanation as conceptual error--
  46. B

    I Should I Remove the Outlier Point in My Linear Fit?

    Hello I have these points coming from different experiments: ##x = [-0.3, -0.2, -0.09, 0.01, 0.2]## ##y = [-8.15, -5.20, -3.32, 0., 5.65]## ##y_{err} = [0.1, 0.27, 0.35, 0.09, 0.44]## and I need to fit a straight line to them (based on theoretical arguments). I attached below the obtained...
  47. Eclair_de_XII

    B Rotating a point in 3-space through an angle about some vector

    Denote ##v=(1,2,3)^T##, ##\theta=\arctan(2)##, and ##\phi=\arctan(\frac{3}{\sqrt{5}})##.The way that I attempted this was by performing the following steps: (1) Rotate ##v## about the z-axis ##-\theta## degrees, while keeping the z-coordinate constant. (2) Rotate ##v## about the y-axis...
  48. A

    MHB Find the intersection point for x = -5 + 8t, y = 1 + 10t, z = 9 + 8t ; -2x + 8y + 8z = 10

    Find the intersection. x = -5 + 8t, y = 1 + 10t, z = 9 + 8t ; -2x + 8y + 8z = 10
  49. E

    Is angular momentum taken about a point or an axis?

    One part of König's theorem states that ##\vec{L} = \vec{L}_{\text{COM}} + \vec{L}^{'}##. The term ##\vec{L}^{'}## simply refers to the angular momentum wrt. the centre of mass. This is just a point, and doesn't have an axis implicitly associated with it (we have infinitely many choices!). The...
  50. D

    Is my elbow the point of application of force of a torque?

    if i pick up a bucket i apply torque to the bucket. my shoulder is the fulcrum. is my elbow the point of application of force? just trying to understand the physics?
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