Couple Definition and 445 Threads

In mechanics, a couple is a system of forces with a resultant (a.k.a.net or sum) moment but no resultant force.A better term is force couple or pure moment. Its effect is to create rotation without translation, or more generally without any acceleration of the centre of mass. In rigid body mechanics, force couples are free vectors, meaning their effects on a body are independent of the point of application.
The resultant moment of a couple is called a torque. This is not to be confused with the term torque as it is used in physics, where it is merely a synonym of moment. Instead, torque is a special case of moment. Torque has special properties that moment does not have, in particular the property of being independent of reference point, as described below.

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

    Just A Couple Of Thermodynamics Questions

    Please help! I have an assignment due tomorrow, and there are two parts of questions that I cannot get :S Homework Statement A substance has an isothermal compressibility of k=-a/v and an expansivity B=2BT/v, where "a" and 'b" are constants. The equation of state is v-bT2+aP=constant (I...
  2. DocZaius

    Uncovering Newton's Thoughts on Friction and Momentum: Couple Questions Answered

    Couple questions regarding Newton: 1) Sort of a historical question...In Newton's time, how did Newton explain the stopping of an object due to friction? I imagine that would have been the first objection to his first law. Could he have said that the Earth's momentum had changed due to the...
  3. J

    Couple of questions on evolution

    1. Is the common ape ancestor common for all the human races? 2. Why don't we see another non-human animal, but very similar to humans-in terms of brain power? For every non-human animal, there exist other species, somewhat similar in terms of appearance or skill set. Did human's advanced...
  4. F

    A couple of limit computations

    Homework Statement Compute the limits. If they don't exist, then explain. 1) lim as x approaches 0 [cos(x) - 1] / [sin^2(x) + x^3] 2) lim as x approaches 0 √(x^2 + x^3) / (x + 2x^2)Homework Equations The Attempt at a Solution 1) I replaced the sin^2x in the denominator with 1 - cos^2x and...
  5. B

    Couple questions about speakers and speaker boxes

    1) Why might speaker boxes differ in shape? 2) Why might some speakers be bigger or heavier than others? 3) Why are speaker surfaces made of materials other than regular paper or styrofoam?
  6. D

    [Guidance needed]-Compute the Magnitude and Direction of the Resultant Couple

    Hello again :). here is a very interesting exercise, I attached a picture of the exercise, its a Circle with Forces. Homework Statement Compute the Magnitude and Direction of the Resultant Couple acting on the body Shown: Homework Equations M=F x D The Attempt at a SolutionCan you provide...
  7. D

    Couple Multiple Choice questions on force and centripetal acceleration.

    #1) A child ties a .25kg rock to the end of a string and whirls it at a constant speed in a horizontal circle of radius 75 cm. What, approximately, is the maximum speed at which the stone may be whirled if the string will break for a tension exceeding 300N? A. 10 m/s B. 13 m/s C. 15...
  8. K

    Electrochemistry of galvanic couple in an acidic solution

    Homework Statement From the perspective of corrosion...Gold and Copper II are joined together and immersed in a 1Molar HCl solution. What possible half-cell reactions and full cell reactions can occur? Which one is most likely to proceed?Homework Equations Half-cell potentials for Au^{3+} +...
  9. S

    A couple of Integration problems

    A couple of Integration problems 9dx/(x(x^4 + 8 )) Homework Statement Hi I'm new to this forum. I have a couple of Integration Problems which I am not able to integrate correctly. I will also post my attempt at solving the problem so u guys can see what method i took trying to solve...
  10. G

    Can You Identify Which Iron Bar is Magnetic Without Any Tools?

    1. How can something travel faster than light? 2. You have two identical bars of iron – except that one is a magnet. Without using any piece of apparatus, or any other object, how can you find out which is which? Hope you can help Thankyou :)
  11. S

    A Couple Deceleration Questions

    (1) 1. Homework Statement Determine the stopping distance for a car with an initial speed of 95km/h and human reaction time of 1.0s, for an acceleration (a) a = -4.0m/s^2 Initial velocity (V1) = 95 km/h = 26.38 m/s Final velocity (V2) = 0 m/s Initial Displacement (Y1) = ? Final Displacement...
  12. R

    Couple of relative velocity problems.

    1. A swimmer heads directly across a river, swimming at 1.7 m/s relative to the water. She arrives at a point 44 m downstream from the point directly across the river, which is 76 m wide. (a) What is the speed of the river current? 1 m/s (b) What is the swimmer's speed relative to the...
  13. R

    Movie theaters that have a couple of seats where you can't see the movie.

    Have you ever been to a movie theater where there are seats that are out of view to the movie? A Regal Cinema near me has a couple of seats that are like that. If you sit in one of them you totally can't see the movie. What were they thinking when they put those seats in?
  14. M

    Find Moment and Force in 3-D Plane

    I really don't need an answer to a question but I'm trying to show there are two ways to find the moment about an axis in a 3-d plane when a force is being applied. I know you draw the "r" vector from the axis to the point of where the force is being applied, but sometimes there are two...
  15. U

    A couple of Infinite Series questions

    a couple of "Infinite Series" questions... Hi, I'm trying to solve some problems in "Stroud's Engg mathematics"... I'm stuck with these 2 questions: Σ (r=0→∞) (2r) / (r+1)! and Σ (r=0→n) (2r-1) / r(r+1)(r+2) the 1st question converges to 2. My 1st try is divide everything the...
  16. P

    Couple questions on acceleration and velocity

    1. Santa loses his footing and slides down a frictionless, snowy roof that is tilted at an angle of 35°. If Santa slides 6 m before reaching the edge, what is his speed as he leaves the roof? 2. 1000 kg weather rocket is launched straight up. The rocket motor provides a constant acceleration...
  17. P

    Couple of simple (I hope) questions

    Homework Statement 1st problem I'm struggling to answer this question using my calculus workbook. Find the point of intersection of the lines: y_{1}=3x+2 3y_{2}=16-x I can solve this question as a simultaneous equation, but, as it is in my calculus question paper believe it to...
  18. N

    Couple of uncertainty questions

    1. The area of a circle has a fractional uncertainty of 0.08 (i.e. 8%), what is the fractional uncertainty of it's radius? So i suppose you have to use A = pi(r^2) and rearrange, bit confused though... 2. Square wave has a height of 2.4cm +/- 0.2cm. This signal is applied across a resistor...
  19. P

    Determine the value of the couple

    Consider the drawing of the lever. Determine the value of the couple, M, so that the resultant of the applied loads passes through the point O. The applied loads include the two forces (400 N, and 320 N), and the couple M. M=400\times0.15\timescos30+320\times0.3=148(Nm) Is this equation...
  20. K

    Force couples - Finding resultant couple

    Homework Statement The steel plate shown supports six 2 in. - diameter idler rollers mounted on the plate as shown. Two flat belts pass around the rollers, and rollers A and D are adjusted so that the tension in each belt is 10 lb. Determine (a) the resultant couple acting on the plate is a...
  21. J

    Answer check for a couple fourier series problems

    Homework Statement hello, so I've got a couple of problems I need someone to kind of check over because on one of them, I'm not sure if it's correct, and then the other looks to be incorrect. For problem 1, we have a 2\pi periodic function where f(x) = xsin(x) For the second problem, I...
  22. DocZaius

    Couple questions regarding batteries

    Hello there! Couple questions: 1. When a battery's terminals are connected by a copper wire, why is that called a circuit? Aren't the electrons moving, as a result of voltage difference, from the anion compartment of the battery to the cation compartment in a one-way direction? The fact...
  23. D

    Solving Physics Exam Problems: Quadratic and Torque Examples

    I just wrote a physics exam today and I got stumped on a couple problems that have been bugging me, and I should probably find out how they are done the right way, or at least how to set them up just in case I use them again and I don't see any examples in my textbook: The first I'm pretty...
  24. C

    Another couple of integration porblems

    Back for a couple more I'm having a little trouble with. The first is sech(1/x)tanh(1/x) all over x^2 Here I'm not sure how to deal with integrating hyperbolics at all as we haven't gotten to it in class yet. I did some searching on the internet and found that the integral tanh(x)sech(x) =...
  25. M

    A Couple Exam Review Questions

    Ok, I'm reviewing for my exam and I'm having issues with a few of the answers they have given... Let me know what you think. This practice exam seems a little iffy to me... There seem to be mistakes in it all over. One question asked the angular momentum of the Earth and said the answer was just...
  26. P

    Generalized coordinates of a couple harmonic oscillator

    Homework Statement Suppose there is a square plate, of side a and mass M, whose corners are supported by massless springs, with spring constants K, K, K, and k <= K (the faulty one). The springs are confined so that they stretch and compress vertically, with unperturbed length L. The...
  27. S

    Are These Probability Problems Solvable with Bayes' Theorem?

    1. An urn contains 2 white balls and 8 red balls. A second urn contains 8 white balls and 2 red balls. An urn is selected, and the probability of selecting the first urn is 0.4. A ball is drawn from the selected urn and replaced. Then another ball is drawn and replaced from the same urn. If...
  28. H

    A couple basic conceptual questions

    Question 1: I was told here that in Case A, the torque is equal to zero. I'm not really seeing that. I know torque is equal to rFsin\theta. If I draw a vector from the rotation point (the very center of the spool) to the point where the force is being applied, I get that the force and r...
  29. D

    Calculating Beam Moment: Equation for Couple Acting on Supported Beam

    Homework Statement Hi I have a beam that is supported at one end and at the other has a point moment (couple) acting on it at the end point. I was wondering the follwing equation is correct for the moment at any point on the beam. M= Cx/L Where M is the moment, C is the force of the...
  30. G

    What are some strategies for solving limit problems involving zero or infinity?

    Hello. I have a couple limit problems for my homework and I'm not sure what to do with them. 1. lim x->0 of (a^x - b^x)/x = ? I see that as x goes to zero, the top goes to 1-1 which would make the whole thing zero, but at the same time the bottom goes to 0 but you can't divide by zero of...
  31. L

    I have a couple of questions on archimedes' principle

    the question is: consider that a balloon filled with 1 liter of water (1000 cm^3) in equilibrium in a container of water, what is the mass of the liter of water? what is the weight of the 1 liter of water? what is the weight of water displaced by the balloon ? what is the bouyant force on...
  32. U

    Calculating Couple Moment - Explaining Negative Values

    Hey, I'm having some difficulty calculating couple moment. i understand that \sumM = \sumFd. here's an example: it asks to resolve the couple forces. the answer is: (4/5)(60lb) = 48lb and (40lb)(cos30) \sumM = -(48lb)(4ft) + (40lb)(cos30)(8ft) Now, i don't understand why...
  33. N

    Redox Reactions: Identifying and Understanding Chemical Transformations

    Which of the following is a redox reaction? A. TiCl4(g) + 2 Mg(l) D Ti(s) + 2 MgCl2(l) B. NH3(g) + CO2(g) + H2O(l) NH4HCO3(aq) C. NaCl(s) + NaHSO4(s) D HCl(g) + Na2SO4(s) D. NaOH(aq) + H3PO4(aq) NaH2PO4(aq) + H2O(l) E. None of the above Is it A? Also another q. The primary reason for...
  34. W

    Moments Of A Couple probably just something simple.

    Homework Statement http://i124.photobucket.com/albums/p27/lollipopgourmet/untitled.jpg If the couple has a magnitude of M, determine the magnitude F of the couple forces. Since this is an X-Y plane, I assumed the equation would simple just be M=Fd, where I know the moment, and just have...
  35. S

    New to forum and having major problems with couple problems

    New to forum and having major problems with couple problems! 1)Two cars are towing a housing unit to a new location. The sum of the forces vector F A and vector F B exerted on the unit by the horizontal cables is parallel to the line L, and FA = 3200 N. Fa(angle)=48, Fb(angle)=32 Determine FB...
  36. L

    Solving Electric Fields in Surface Charge Density Problems

    ok if you could just tell em if this sounds alright. (i) A large horizontal sheet of surface charge density \sigma has a hole of radius b cout out of it. Find the electric field directly above the centre of the hole. I already have expressions for the electric field due to the sheet and...
  37. R

    Find Eqv force and couple at point

    Hey everyone, I'm really stuck on a review of statics for Solid Mechanics. I got through everything but this problem. I know there has to be two forces at point a if it's attached to the wall(Ax,Ay). I would say I'm stuck trying to figure out how I can move two forces that are unkown into a...
  38. P

    How Does Helmet Design Impact Safety and Collision Outcomes?

    A couple of physics questions on helmets!? 1. Why is the impact force reduced for a helmet with a soft interior vs.a hard interior? 2. How is the safety reduced if the helmet does not fir properly? 3. Once a helmet has been involved in a collision, it should be replaced. why? 4. What...
  39. L

    New to the board. Can I get some guidance on a couple of questions?

    Homework Statement 1) The drawing shows a person looking at a building on top of which an antenna is mounted. The horizontal distance between the person's eyes and the building is d = 68.0 m. In part a the person is looking at the base of the antenna, and his line of sight makes an angle of θ1...
  40. H

    A Couple of Probability & Statistics Questions

    Homework Statement I have a table with a data set #, and 2 variables (W and P) with values in the table. Homework Equations The equation (which I don't know what it means) says V= (summation with n on top and i=1 below Wi X Pi)/(summation with n on top and i=1 on bottom X Pi) The...
  41. M

    Can light be trapped forever between two perfect mirrors?

    1. If gravity waves travel at the speed of light and it take about 8.5 minutes for to reach Earth from the sun, If the sun suddenly collapsed into a black hole would it take 8.5 minutes for us to start being pulled in? 2. If you could somehow set up 2 mirrors facing each other than...
  42. M

    Solving Log Equations: A Couple of Tricky Questions | Homework Help

    Homework Statement 1.) 3logx2y + 2logxy 2.) 4logabc - 2loga2b - 3logbc Homework Equations The Attempt at a Solution I know that 3logx2 is the same as 6logx but I don't know what to do since there's a y there
  43. M

    Couple of algebra questions I'm struggling with

    Homework Statement 1.) a.) If the roots of equation px2 - 4x + 1 are equal then find value of p b.) Prove that the equation (k - 2)x2 + 2x - k = 0 has real roots (upside down A symbol) k E R Homework Equations The Attempt at a Solution I just don't know how to approach these...
  44. H

    The math behind a couple of theories

    I was just wondering, what math is needed to fully understand the mathematics of general relativity, quantum mechanics, and string theory? Can you be specific in naming them? For example General Relativity Algebra Calculus I know there has to be more than that but that was an example...
  45. M

    Couple of questions on linear geometry

    I know the formulas for coordinate geometry of the straight line and I've done a fair bit of it but I have trouble when it comes to converting equations into lines with coordinates. Heres an example of a question I can't answer L is the line 2x - 3y - 7 = 0. Verify that the point a(-1,-3)...
  46. K

    The standard model, a couple of q's

    I have a couple of questions about the standard model: 1.) I read somewhere that the standard model describes 3 closely related Yang-Mills systems, but i thought yang-mills systems were non-abelian whereas U(1) is abelian. So is the statement false or have i misunderstood? 2.)Why do i see...
  47. M

    A Couple of Practice Questions

    I need help with some physics questions. (Grade 11 Physics) Any help appreciated... 1. Assuming that the effective force of friction is 225N, what is the minimum work needed to push a 1.00 x 10^3kg car 45.0m up a 12.5 degree incline? 2. A 2.20kg pendelum has a period of 4.0 sec a)...
  48. S

    Can you give a couple of examples of chemical energy?

    Can you give a couple of examples of chemical energy?
  49. F

    Idiot trying to grasp relativity with a couple questions

    I am no scientist, nor did I stay at a Holiday Inn Express last night. I have been trying to understand this theory for a while, but it seems that my questions never get answered in what I read. Either that, or I am just too stupid to get it. As an example, I have been reading "The Dogschool...
  50. M

    A couple of geostationary calculations

    Homework Statement a satellite is orbiting the Earth in a near-polar orbit. it's orbital height is 500km. the satellite carries a nadir-viewing push-broom scanning imaging instrument with 4 spectral bands. for each spectral band, the detector array consists of 1024 detector elements. the width...
Back
Top