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. D

    Velocity of bodies in contact

    If both bodies are in motion and come into contact, say a ring sliding on a block in motion as well. The speed of the ring (RPM) and the speed of the block in motion would both change once the bodies come into contact. Is there a way of calculating what the speeds of both bodies would be...
  2. D

    Can the speeds of bodies in contact be predicted using physics principles?

    Hi, Maybe this is more a mechanical question, but here goes. In a ring on block wear test, if both bodies are in motion, the speed of the ring (RPM) and the speed of the block in motion would both be differ on contact from what the were originally were. Is there a way of calculating...
  3. L

    Contact mechanics, elastic bedding

    Contact mechanics, "elastic bedding" Hello! I need some help regarding my problem. I have a solid shaft with a mounted ring on it. The has a higher E-modulus than the shaft. A force F is acting downwards on the ring. As seen in the picture. The force could be assumed to be a point load if...
  4. C

    Kinetic Energy of rod with lower end in contact with smooth surface

    Homework Statement I've got a rigid rod, length 2a, held at an angle \alpha above a smooth horizontal surface. Its end is in contact with the ground. My two generalized coordinates are x, the horizontal position of the center of the rod and \theta the angle between the rod and the vertical...
  5. R

    Mechanics - contact forces

    Homework Statement A body of mass m = 10kg is suspended by a fixed support through a perfect wire. The body is resting on the vertical support to another disk, so that the thread formed with a vertical angle α = 45 °, as shown. The tension from the wire has the value: a. T = 41N b. T =...
  6. R

    Do Normal Forces Always Exist When Surfaces are in Contact?

    Homework Statement Is it necessary to have a normal reaction whenever 2 surfaces are in contact with each other? The Attempt at a Solution I thought the answer was "no". But my book says "yes". I can support my answer with an example: the normal force between the surface of a block...
  7. B

    Light a light bulb with no contact?

    Hi, Is it possible to make a standard light bulb light without any physical contact to it (appart from support)? I seem to remember seeing such an experiment, but can't remember the details. Thanks
  8. K

    Frictional Moment produced by contact between rotating and non-rotating surfaces

    [b]1. This problem is part of an engineering model I am working on for a class. I am ultimately trying to model the torque applied to a bottle as a function of the static/kinetic coefficient of friction between it and the rubber cone it is being torqued by (The reason for this being bottle caps...
  9. Galileo

    What does this eye contact signal mean?

    I'm usually not too consciously aware of other people's body language. I don't want to read, then interpret, then act on the interpretation of someone's body language consciously. However, I've noticed something and I'm extremely curious as to what it means. Whenever I really want to create an...
  10. K

    Charge by Contact: Net Charges on Each Sphere?

    Homework Statement Two uncharged spheres are touching (they are held by insulating stands). A negatively charged rod touches the sphere on the left. After, rod is taken away and the adjacent sphere (the one that the rod did not touch) is separated. What are the net charges on each sphere...
  11. S

    Contact force, EM force and the loop

    The maximum I have found about contact force is very roughly this: it is nothing but electromagnetic force, meaning that, if two bodies collide, the electrons of the atoms of the outer shell of each body repel each other, those atoms displace towards their neighbours and repel them in turn, thus...
  12. R

    Distance between polygons in 3d? (points of contact as a function of time)

    I was just wondering, is there a way to write a polygon as an equation in 3d? (Yes, a polygon, NOT a polyhedra) It's intended to be a part of a collision detection program, so I need to be able to represent all points on a given polygon as an equation. Each polygon is being acted upon by...
  13. M

    2 Identical Objects in Thermal Contact

    If 2 identical objects with initial temperatures X and Y are placed together in thermal contact, then the final temperature is T= (X + Y)/2, X and Y actually being equal and excluding any heatloss to surroundings. I understand this intuitively, but is there a precise mathematical proof? It's...
  14. E

    Forces on a body in contact with a horizontal plane

    1. The drawing shows a 27.4-kg crate that is initially at rest. Note that the view is one looking down on the top of the crate. Two forces, and , are applied to the crate, and it begins to move. The coefficient of kinetic friction between the crate and the floor is k = 0.313. Determine the (a)...
  15. P

    How to Calculate Contact Force Between Boxes in Physics?

    Homework Statement As shown in Figure 5-19, a force of magnitude 7.50 N pushes three boxes with masses m1 = 1.30 kg, m2 = 3.10 kg, and m3 = 5.80 kg. Figure 5-19 the figure depicts 3 boxes, in order m1, m2, m3 with a force pushing directly on m1 to the right on a flat level surface...
  16. N

    Contact Transformation Problem

    Homework Statement If an infinitesimal segment of a curve (dy,dx) in a 2-D space, having a slope p, is transformed to (dY,dX) with a new slope P, find the transformation to do this. Such a transformation should be called a ‘contact transformation’. Homework Equations The Attempt at a...
  17. B

    Calculating Magnitude of Contact Force Between Boxes 1 & 2

    Homework Statement A force of magnitude 9.00 N pushes three boxes with masses m1 = 1.30 kg, m2 = 2.80 kg, and m3 = 4.90 kg Find the magnitude of the contact force between boxes 1 and 2. Homework Equations Fnet,x = ma? The Attempt at a Solution I thought that it would be 9.00 N...
  18. I

    Contact Forces with a Massless String

    Homework Statement Three blocks of equal mass (m = 0.88kg) are placed in a row onto a rough ramp (μ=0.77) whose angle of inclination is 35 (degrees). Each block is connected to the other by a massless string. Suppose you pull upwards on the top block with a force of 34.9N. Answer the...
  19. I

    Contact Forces Question(s) part 2

    Homework Statement Three blocks are placed onto a frictionless horizontal surface. These blocks are side by side and are in contact with each other. Let m1=2m2=5m3. Answer the following exercises. (Part 1) a)If a force is applied to m1, then show that i)Fa = 17/2m3a ii)F12 = 7/2m3a...
  20. I

    Contact Forces in Three-Block System

    Homework Statement Three blocks are placed onto a frictionless horizontal surface. These blocks are side by side and are in contact with each other. Let m1=2m2=5m3. Answer the following exercises. a)If a force is applied to m1, then show that i)Fa = 17/2m3a ii)F12 = 7/2m3a where...
  21. S

    Find Contact Force Between Two Blocks: M1=1.75kg, M2-3.38kg, F=6.10N

    Problem two blocks are in contact on a frictionless table. a horizontal force F is applied to M2. if M1=1.75kg, M2-3.38kg, and F=6.10N, find the size of the contact force between the two blocks. So i am just not sure how to find contact force cause my teacher never taught it to us...
  22. R

    Calculating Contact Forces Between Three Blocks on a Frictionless Surface

    Homework Statement Three blocks on a frictionless horizontal surface are in contact with each other. A force F is applied to block A (mass mA ). If mA=mB=mC=10.0 kg and F = 96.0 N, determine the force of contact that each block exerts on its neighbor. Homework Equations The Attempt...
  23. G

    Physics Physicist. Stay with intellectual tasks. More people contact. -> Consulting, ?

    I'm graduating in physics and got the feeling that I prefer a career with more team work unlike being a sole researcher. I know they meet and discuss stuff, but yet I prefer something more dynamic than standard research. And also more multifaceted tasks would be ideal. I like to analyse problems...
  24. S

    Shaft hertzian contact stress?

    Hello I am trying to calculate contact stress for a shaft on a hole. The purpose of this calculation is to see if the diaphram on which the hole exists is thick enough to handle the shaft radial load. Easiest approximation would be to use a simple formula for bearing stress (stress = force /...
  25. M

    Medical Questions About Contact Lenses and Laser Eye Surgery

    have absolutly no idea where to put this but ill put it here My eyesight is something like +6.25/+6.50 Now the eye man (optomotrist?) said that they only make contact lenses that go up to +6. I was wondering why this is? Also why can't long sighted people have laser eye sugery? Is there...
  26. H

    Understanding Hertzian Contact Stress in Pin-Link Connections"

    As shown in the attachment, the link (blue) is connected to two pins A and B (red). Force is applied by the pin A on the link along the x direction purely. A reaction force is expected at the corresponding point of contact between the pin B and the link I am told that the compressive...
  27. R

    Accidental contact with a radioactive substance

    If I came into accidental contact with a radioactive substance, and it got say on my hands and watch. Obviously I can wash my hands off, but also could I ujust wipe the contamination off the watch? Or would it remain contaminated? Thanks.
  28. russ_watters

    Should we contact uncontacted tribes?

    Another spinoff from the uncontacted tribes thread. A couple of arguments/points were made about leaving uncontacted tribes alone: -The history of intervention has, to put it mildly, not been good. -If we follow some version of Star Trek's "prime directive", we should let them develop in...
  29. A

    Investigating the contact times between a golf club and a golf ball

    Homework Statement While investigating the contact times between a golf club and a golf ball, a student wanted to measure the contact times between metal objects – looking at how various factors (such as the material from which they were made, their mass, their speed on impact) affected the...
  30. J

    Calculating Speed of Golf Ball After Contact

    Homework Statement i hit a golf ball of mass 0.045kg with an avg. Force of 2.5x10^3 N over a short time interval of 1.0 x 10^-3 s at an angle of 30 degrees with respect to the horizontal. neglect air resistance and assume a level course. What is the speed of the ball immediately after...
  31. A

    PMMA Hydrophobic: Explaining Molecular Level

    I'm just wondering why PMMA (polymethylmethacrylate) is hydrophobic and does not attract water. I can't find anything that explains this on a molecular level :S
  32. M

    Investigating Contact Stress in HighSpeed Pipe Rolling

    Contact Stress? I have a "High Spin" rolling system that spins pipe to compact cement lining. We are using tandem 7-14.5LT D/8 bias-ply tires on each end of the axles with the pipe riding in the saddle between two sets of tires. The tires are running approx. 70 MPH for just over a min. The...
  33. R

    What is the Radius of Curvature of the Outer Surface of a Contact Lens?

    [SOLVED] Contact Lenses Problem Homework Statement A contact lens is made of plastic with an index of refraction of 1.58. The lens has a focal length of +26.0 cm, and its inner surface has a radius of curvature of +20.0 mm. What is the radius of curvature of the outer surface? Homework...
  34. C

    Bending stress of beam in contact with a flat surface?

    I am designing a spinal disc with 2 metal endplates. These endplates are rectangular in shape and are fixed to form a flat contact surface with the vertebrae bone surface. My question is based on the bending stress of these metal endplates. I need to work out the possible thickness of these...
  35. S

    Calculating Contact Forces between Blocks

    Homework Statement Three blocks are in contact with each other on a frictionless, horizontal surface, as in Figure P5.54. A horizontal force F is applied to m1. Take m1 = 2.00 kg, m2 = 3.00 kg, m3 = 4.00 kg, and F = 22.0 N. (c)What is the magnitude of the contact force between m1 and m2...
  36. A

    Find the Contact Force Between Two Blocks

    Two blocks are in contact on a frictionless table. A horizontal force F is applied to M2, as shown. If M1 = 1.51kg, M2 = 3.96kg, and F = 4.55N, find the size of the contact force between the two blocks. So first I found the acceleration (F=ma) 4.55/(1.51+3.96) = 0.83 = acceleration Im...
  37. S

    Find Contact Force Between 2 Blocks

    [SOLVED] Contact Force Homework Statement a.Two blocks are in contact on a frictionless table. A horizontal force F Is applied to M2. The force's magnitude is 4 N. [The diagram shows the force pushing on the left side of M2, which has M1 on its right side.]If M1=1.09 kg, M2=3.02 kg, find the...
  38. D

    Which Rod Transfers More Charge to a Metal Ball?

    Let's say we have a charged plastic rod and a neutral metal ball, and a charged metal rod and neutral metal ball, which rod can transfer more charge onto the metal ball? Or metal ball onto the rod (if the rods are positive) Thank you
  39. P

    Carl Sagan's "Contact": Read or Watch the Film for a Religion vs. Science Debate

    "contact" by carl sagan I hear they are showing Cosmos by carl sagan again on tv but something else of carl sagan's worth knowing about is his novel "contact". If you don't have time to read the book watch the film staring Jodie Foster and Mathew McConnaughey - it is awesome, and the best film...
  40. C

    Ball and socket contact stresses

    I am familiar with Hertzian contact mechanics for spheres in contact with a falt surface or a sphere in contact with another sphere. However, I am unsure on how to model a ball and socket contact? Could anyone help me with this idea please? Thanks
  41. J

    Solving the Mountain Climber Problem: Tension & Contact Force

    Homework Statement A mountain climber is rappelling down a vertical wall. The rope attaches to a buckle strapped to the climber's waist 15 cm to the right of his center of gravity and makes an angle of = 15° with the wall. The climber weighs 780 N. (a) Find the tension in the rope N...
  42. E

    Medical Contact Lens Safety: Are They Dangerous for Eyes?

    are contact lenses dangerous for eyes? i hate glasses. another question is that is there any contact lenses which are colored and also do glasses job too?
  43. H

    Hertz Contact Stress: Calculating & Comparing Allowable Stress

    HI All: Using Hertz contact formula I calculated contact stress for cylinder in contact with cylinderical socket but I don't know to which stress to compare this contact stress.Actally I comapred with material bearing stress & calculated stress was less that bearing stress(got margin of...
  44. M

    HELP: contact area of Cylinder inside a larger Cylinder?

    Laydies and Gents can anyone help me here? suppose there are well known formulas for this. That is, contact area of a known size cylinder lying inside a larger know size cylinder... hope problem is clear thank you best regards martin
  45. T

    Calculate Contact Force: Car and Truck Collision on Icy Road

    Homework Statement A car of mass 8.50E+2 kg and a truck of mass 3.55E+3 kg run into one another due to ice on the road. 60.0 ms after the collision, the car is pushing on the truck with a force whose magnitude is 1.56671E+5 N. Calculate the size of the force on the car due to the truck at...
  46. O

    When you touch something there isn't really any physical contact

    When you touch something there isn't really any "physical" contact When you touch something there isn't really any "physical" contact, it's just the electromagnetic forces that repel each other. So if I try to touch a table, no particles from my hand actually touches any particles from the...
  47. A

    Does friction depend on area of surface of contact?

    dont have much time, ll make it quick does friction depends on area of surface of contact?? i don't think it does:confused::confused:
  48. P

    Discover the Benefits of 'Day and Night' Contact Lenses

    Which contact lenses do you like the most? For me it's 'Day and Night' although I take it out in the night just to let the eyes breathe better.
  49. L

    Create Contact Form Without PHP Scripts

    Hello, I need a contact form on my website, that will send to my email address what the visitor enter in the form fields. The problem is that I can't run any php scripts.. is there a way to use some html form? :smile:
  50. C

    Three Blocks with Forces: Calculating Contact Forces

    Three blocks are in contact with each other on a frictionless horizontal surface with m1=1kg m2=2kg m3=3kg A horizontal force of 24N is applied to M1. a) Find the acceleration of the three blocks b) Find the net force on each block c) Find the magnitude of the contact forces...
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