What is Contact: Definition and 447 Discussions

Contact dermatitis is a type of inflammation of the skin. Some symptoms of contact dermatitis can include itchy or dry skin, a red rash, bumps, blisters, and swelling. The rash isn't contagious or life-threatening, but it can be very uncomfortable.
Contact dermatitis results from either exposure to allergens (allergic contact dermatitis) or irritants (irritant contact dermatitis). Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight. Diagnosis of allergic contact dermatitis can often be supported by patch testing.

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  1. Parzeevahl

    Entropy change for water in contact with a reservoir

    Problem Statement: 1 kg of water at 273 K is brought into contact with a heat reservoir at 373 K. When the water has reached 373 K, what is the entropy change of the water, of the heat reservoir, and of the universe? Relevant Equations: dS=Cp*(dT/T)-nR*(dP/P) dS=Cv*(dT/T)+nR*(dV/V) I am...
  2. S

    Physical explanation of eye contact

    Is it not fascinating that you can feel eye contact on such distances we do? What is it that we actually detect? I understand that the eye absorb light, it may be the starting point for the explanation?
  3. Zouatine

    Minimizing the area of a channel in contact with water

    My problem: In the solution,our teacher found, that the wet section is minimal if y=L/2 So Am: = L^2 /2; Pm: = 2L; So despite that I try with any value, I can not find a more minimal section, and that's not the case because if I try with y = L / 3 I find Am: L^2/3; Pm: (5/3)*L ; and these...
  4. Kasiopea

    Determine the forces exerted by the supports on the pipes at contact s

    I tried to solve it and I got that the forces on the cylinder A are: F_1= 58.8 and F_2=58.8 Cylinder B are: F_3=117.6 and F_4=117.6 Cylinder C are: F_5= 58.8 and F_6=117.6 Can someone help me with this?
  5. Wrichik Basu

    What type of electrical contact joint is this?

    While working on an old electric iron, I found this joint in the wires: Any idea what this joint is? Does it have a special name? The wires are in a horrible condition, so I have to change them. How can I build this joint by myself? Or are such wires readily available in the market?
  6. B

    B But WHY do antimatter and matter annihilate on contact?

    Everyone knows that matter and antimatter annihilate upon contact. But exactly WHY this should happen is not at all obvious, at least to me. So what exactly happens when two such particles encounter one another that leads them to disappear in a large release of photons? And for that matter...
  7. M

    I Parameterize a circle based on the contact angle with a wedge

    Hi PF! Given a 2D plane, the following is a parameterization of a circular arc with contact angle ##\alpha## to the x-axis: $$\left\langle \frac{\sin s}{\sin\alpha},\frac{\cos s - \cos\alpha}{\sin\alpha} \right\rangle : s \in [-\alpha,\alpha]$$ However, I am trying to parameterize a circle...
  8. OWN9494

    Misc. Lifting vehicles with 4 points of contact

    Hello all. Just a quick fyi...I have never taken a physics class although I did want to in high school (many years ago). I am just looking for an answer to a very complicated (yet simple looking on the outside) problem I am having. In my job (towing 13 years) I use physics daily even though I...
  9. dwight_v

    Final temperature for two blocks of iron placed in contact

    Homework Statement Two blocks of iron, one of mass m at 10.0C and the other of mass 2m at 25.0c, are placed in contact with each other. If no heat is exchanged with the surroundings, which of the following is the final temperature of the two blocks? A)10 B)15 . D) 20C ( this is the answer) The...
  10. devilish_wit

    A question about contact forces and friction

    Homework Statement Two blocks of masses m1 and m2 are placed on a table in contact with each other as shown in the figure below. The coefficient of kinetic friction between the block of mass m1 and the table is μ1, and that between the block of mass m2 and the table is μ2. A horizontal force of...
  11. J

    A 2-d and 3-d model for contact resistance of M/n-Si (book?)

    Hi, We're studying Contact resistance and the professor has given assignments on contact resistance. But I can't find any books to refer to. Here is one sample question: The books I'm referring to are ones by Donald Neaman, SMZ, Kanos. but none of them have any mention of 1-d or 2-d model for...
  12. W

    A Defining a Contact Structure Globally -- Obstructions?

    Hi, Let ##M^3## be a 3-manifold embedded in ##\mathbb R^3## and consider a 2-plane field ( i.e. a Contact Structure) assigned at each tangent space ##T_p##. I am trying to understand obstructions to defining the plane field as a 1-form ( Whose kernel is the plane field/ Contact Structure) Given...
  13. LLD1231

    Science review of the movie Contact?

    I’m curious as to what you guys thought of the movie Contact. How well does it stand up to science and physics?
  14. N

    Find the angle for which both disks are no longer in contact

    Homework Statement A mobile disk of radius R and mass M is moving above another immobile vertical disk of the same radius. Initially the mobile disk is at rest at the highest point above the immobile disk and then it starts rolling without slipping. Assuming the mobile disk never slips, find...
  15. G

    I Hertzian contact theory on sin and cosine plane

    Hello guys, i`m currently making simulation of 2 dimension rolling disk on elastic sin/cosine plane. I`m just wondering if the theory applicable.
  16. G

    I Liquid metal slip/rotary contact

    are there any already existing devices on the market or possible ways in which one can make a liquid metal slip contact like a mercury contact in which the mercury can be held at a specific location within a confined space with the help of magnetic field? I know that mercury itself is very weak...
  17. Gabriele99

    How long will the ball and the spring be in contact?

    https://physics.stackexchange.com/questions/407908/if-i-push-a-ball-on-a-string-till-this-is-completely-compressed-how-long-will-t. This is my complete question. I've been wondering on this topic for quite a while. I really can't visualize what happens at the border between the spring and the...
  18. DylanXO

    Contact Lenses Optics Problem (Two-Parts)

    I believe I have answered the first question correctly (although I am not certain of this). And I'm struggling with grasping how to approach the second part of the question. Any guidance or recommedations on reading material would be greatly appreciated. Homework Statement Contact lenses are...
  19. T

    Hollow cylinder magnet making contact with the circuit

    Homework Statement 1. Circuit moves downward while cylinder magnet is fixed. 2. Cylinder magnet moves upward while circuit is fixed. Gain emf in circuit. Homework Equations All those maxwell equations... F=v x B The Attempt at a Solution [/B] So first question is not that hard...
  20. Manoj Sahu

    Why do we use a Contact Resistance Measurement test?

    I was wondering about contact resistance measurment test. Why do we take such test?
  21. R

    I How Do Attractive and Repulsive Electromagnetic Forces Combine in Contact Force?

    If friction is electromagnetically attractive force and the normal reaction is electromagnetically repulsive force which it obviously is. But how is it possible to have different type of force as the component of a single force i. e. Contact force over the nature of which I have got confused!
  22. R

    Optics question: I need parallel illumination for a Contact Image Sensor (CIS)

    I am experimenting with a CIS from a document scanner (basically a row of photo sensors). I want to detect the position of an object as it passes the scanner bar. Initially in one dimension - x along the CIS. If the object is always a set distance from the light bar, I can provide illumination...
  23. Alexanddros81

    Calculate the contact force between the skis and the track

    Homework Statement 14.37 A 75-kg ski jumper starts his run in the position shown on the parabolic track. The equation of the parabola is ##y = (12/225)x^2##, where x and y are in meters. Neglecting friction, calculate the contact force between the skis and the track at O. Homework...
  24. Richie Smash

    Motion of a Door as I Walk by it Quickly (no contact)

    Hey this is just a random question, but recently I've started studying physics, only last year. Before this I never used to question really a lot of things i took for granted, but now I see the world with a different light although I'm still quite the novice. Something that used to make me...
  25. BTA

    Why would aliens come here? (resurrected)

    I asked myself this question today, found that exact question asked here (February 10, 2005)... and I could not say anything, not even a squeak. Well, boil that dustmote! "Why would aliens come here?" I ask and the voices in my head speak. We are far from the galactic center of an average...
  26. S

    Two spheres of are dropped to ground while in contact.

    Two spheres of different masses are dropped to ground.They are in contact as one above the other and are of masses, let’s say m and 2m.They are dropped with velocity v - My question is if we can conserve momentum and if we can why?And how to find the final velocity of upper ball after collision...
  27. I

    Dynamic contact angle simulation in COMSOL

    I am doing the dynamic process of a water droplet impinging onto a wax substrate in COMSOL, using the Phase Field method for tracking the free surface. I am able to do the simulation for Static Contact Angle(SCA) i.e i am imposing a fixed contact angle throughout the time step in wetted wall...
  28. J

    I Where is a contact force labeled on a diagram of a pivoted beam?

    Hi...What is a contact force and where is it labelled in a diagram showing a beam pivoted?
  29. D

    Circuit Model for a Rotary Contact?

    Hi Everybody, First post on the forum, this one's stumped me I'm afraid. I'm basically trying to model a rotary connection in an AC circuit, and I'm having a bit of trouble with it. Ideally I'd like a reasonable approximation with conventional circuit elements. Basically I've got a...
  30. Jiri Fila

    Contact strength in ANSYS Workbench

    Hello, I want to model in Ansys Workbench contact between bricks and mortar. From experiments I know maximum normal stress and maximum shear stress. Respectively I know forces in which the contact fails. The failure is brittle due to lost of adhesion. I tried to use "Bonded contact" and...
  31. M

    I Effects of Ultrasonic Transducer in contact with glass

    I'm looking for a way of using ultrasonic cleaning to clean the inside of a glass vessel filled with some sort of fluid by transmitting ultrasounds through the glass, rather than submerging the entire glass vessel. If an ultrasonic transducer, let's say something with a maximum frequency of 40...
  32. T

    Is this point of contact an inertial frame?

    Consider a disc being pulled by a constant force F and it is performing pure rolling. Now, the disc has a certain acceleration, point A has a acceleration in right direction and another centripetal acceleration in vertically upward direction but it has zero instantaneous velocity because of pure...
  33. M

    Ansys Maxwell Contact Resistances

    Hello everyone, I am using Maxwell 16.2 with no chance to get an update. I want to do a 3D design Eddy Current Simulation to find out the Joule losses of my single phase GIS design. An important factor for the joule losses that I need to insert is the contact resistances of the several...
  34. L

    Plot the contact pressure vs axe x (mm) in ansys workbench

    thanks for you sir i want to se how can i plot the contact pressure vs axe x (mm) in ansys workbench.? its very important for me
  35. V

    Charged insulator in contact with conductor

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] This is a quite a fundamental question in electrostatics and I felt pretty embarrassed getting it wrong .I thought correct option was d) . Could someone help me understand how conductor could acquire charge as charges...
  36. tl_ccc

    Nonlinear contact convergence problem in ANSYS Workbench?

    I am using the static structural module of ANSYS workbench to do a simulation. In my model, there is a gear and a spring which presses against the gear, moves along it and pushes it to turn counterclockwise. These two objects are in frictional contact. In my calculation, I always have the...
  37. L

    Cooling Steel Die for Contact Cooling of Aluminium - Advice Needed

    Hi, I am designing a system to cool aluminium through contact cooling. I have a steel die with 9x 20mm diameter cooling chambers. Water is pumped through the chambers which cools the steel die and hopefully the aluminium sitting on top of it. I am looking to find the temperature of the...
  38. D

    Contact force of block on a wall

    Homework Statement In this sketch, the mass m = 1.6 kg is pushed against a wall by force F, as shown, in the horizontal direction. The values of the coefficients of kinetic and static friction for the contact between are 0.81 and 0.84 respectively. The magnitude of F is slowly and continuously...
  39. I

    Finding the optical power of a contact lens

    Homework Statement A farsighted man uses eyeglasses with a refractive power of 2.05 diopters. Wearing the glasses 0.020 m from his eyes, he is able to read books held no closer than 0.265 m from his eyes. He would like a prescription for contact lenses to serve the same purpose. What is the...
  40. Anders Johnsen

    ANSYS Workbench contact problem

    I'm currently working on my bachelor's thesis in mechanical engineering. A part of my thesis is conducting a FEM-analysis on a sump for sewage. I've applied a load on the upper face of the lid for the sump. As a result, the upper layer of the lid has been "pushed through" the lower layer of...
  41. T

    B Existence of depletion layer in contact surface

    in a P-N junction diode, in an equilibrium state, a depletion layer forms in the surface of contact of N type and P type. But the problem is, this layer is formed by diffusion of electron to a lower electron density zone. Why does it always have to form right in the contactt surface? when...
  42. G

    Interaction between two charged surfaces in contact

    Dear all, I'm curious to know how to calculate an interaction. I'm a chemist and I'm not really used to practice Maxwell equations, so I don't have the complete background for that, but I think it may be trivial even for a physicist student. Let's say we have two surfaces, one has a total...
  43. Shardul Khare

    B What's the Difference Between Contact Force and the Normal Force

    Can somebody pls explain this to me?
  44. farolero

    How comes friction is not contact surface dependant?

    according coulomb force of friction is independant of contact surface a tyre car grip goes in function of contact surface and grip is caused by friction this seems contradictory with coulomb is still coulomb view mainstream or has it been corrected?
  45. Adriano25

    Find angle of the sphere losing contact with the surface

    Homework Statement A solid sphere rolls down a hemisphere from rest. Find the angle at which the sphere loses contact with the surface. R = radius of hemisphere a = radius of sphere Homework Equations ΣFr = Macm,r N-mgcosθ = -mVcm2/(R+a) N = mgcosθ - mvcm2/(R+a) eq. (1) Conservation in...
  46. S

    Role of Fermi Contact Interaction in J-Coupling

    I'm having a hard time understanding the mechanism of J coupling in NMR. Why is coupling information only transmitted through bonding electrons with nonzero s-character? For example, why can't coupling information be transmitted through a bond with no s-character, e.g. a retrodative bond...
  47. T

    Absorbed chemicals in contact lenses?

    Dear scientists, I had stupidly put a few boxes of Acuvue Moist Contact lenses together with a plastic bottle of "extra mild dissolvant" (nail polish remover) these stayed in the same bag in a closed cupboard for months before I noticed it. The dissolvant contains Ethyl Acetate, Butyl...
  48. T

    Electrodes liquid contact electromagnetic flow meter?

    Hello, I'm interested in building a small non-invasive battery powered device that wraps around a pressured 1/2" pipe for measuring potable water. From https://en.wikipedia.org/wiki/Magnetic_flow_meter and watching youtube videos, it seems they all use electrodes which contact the liquid...
  49. Experience111

    I Measuring advancing contact angle

    Hi everyone ! I'm currently working on a project for which I need to measure the advancing contact angle of a liquid on a solid, specifically the advancing contact angle of a molten thermoplastic on carbon fibers. My understanding is that there is a difference between dynamic contact angles...
  50. A

    "ANSYS Workbench" Contact tool results plotting vs length?

    Hello ansys users in ANSYS workbench, how can I plot the contact tool results (Frictional stress, sliding distance...etc) with length (500mm for example) in the "x-axis" instead of the default "by time" option?. the path method can not be used with this type of results "Contact tool results"...
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