What is Circular: Definition and 1000 Discussions

A circular economy (also referred to as "circularity") is an economic system aimed at eliminating waste and the continual use of resources. Circular systems employ reuse, sharing, repair, refurbishment, remanufacturing and recycling to create a closed-loop system, minimising the use of resource inputs and the creation of waste, pollution and carbon emissions. The circular economy aims to keep products, equipment and infrastructure in use for longer, thus improving the productivity of these resources. Waste materials and energy should become input for other processes through waste valorization: either as a component or recovered resource for another industrial process or as regenerative resources for nature (e.g., compost). This regenerative approach is in contrast to the traditional linear economy, which has a "take, make, dispose" model of production.In recent years, concepts based on (re-)cycling resources are increasingly gaining importance. The most prominent among these concepts might be the circular economy, with its comprehensive support by China and the European Union. There is also a broad range of similar concepts or schools of thought, including cradle-to-cradle laws of ecology, looped and performance economy, regenerative design, industrial ecology, biomimicry, and the blue economy. These concepts seem intuitively to be more sustainable than the current linear economic system. The reduction of resource inputs into and waste and emission leakage out of the system reduces resource depletion and environmental pollution. However, these simple assumptions are not sufficient to deal with the involved systemic complexity and disregards potential trade-offs. For example, the social dimension of sustainability seems to be only marginally addressed in many publications on the Circular Economy, and some cases require different or additional strategies, such as purchasing new, more energy-efficient equipment.

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  1. Physkat

    Circular Motion with Tension and Finding Angle

    Homework Statement A 0.020-kg mass is attached to a 1.2-m string and moves in a horizontal circle with a constant speed. The tension in the string is measured at 0.200 N. What is the measure of angle θ? Homework Equations ∑F=ma, a=v^2/r The Attempt at a Solution I broke down the forces at...
  2. A

    Unsure of mechanics problem, circular door on hinge...

    1. In the attached imjage, the centre of gravity of an open door acts at G equal to 255N; a) Determine the x,y,z, components of reaction at the hinge A in equilibrium b) Determine the force along CB Little stuck with this problem, obviously this falls under resolving forces. I assumed Az,Ay = 0...
  3. J

    Calc Speed of Parabolic Arc for Zero-Gravity: NASA's Vomit Comet

    Homework Statement NASA’s Vomit Comet simulates zero gravity by flying parabolic arcs of radius r and speed v to stimulate free fall. If the pilot flies a parabolic path which has a radius of 1km, calculate the speed (*in km/hr) the plane must travel at in order to stimulate free fall...
  4. Z

    Finding static friction from circular motion

    Homework Statement A car traveling on a flat (unbanked), circular track accelerates uniformly from rest with a tangential acceleration of 1.70 m/s2. The car makes it one-quarter of the way around the circle before it skids off the track. From these data, determine the coefficient of static...
  5. J

    Which photons pass through a circular annulus?

    Passing light through a circular sieve: Well, actually, let’s think about radar or microwaves with a wavelength of order a centimeter or two, so you can tailor your aperture, say by etching a silver screen on glass. If you have a reflective metal screen, and you cut a long narrow rectangle in...
  6. D

    Magnetic field at the centre of a circular current loop

    Homework Statement How to calculate the magnetic field at the centre of a circular current (I) loop of radius r using Ampere law Homework Equations B = μ0I/2r The Attempt at a Solution I take circulation along the circular closed path of radius r passing through the center of the loop and...
  7. Mr. Rho

    Outside the origin circular loop current density

    Hi, I'm trying to write the current density for such circular loop in spherical coordinates. For a circular loop of radius a that lies in the XY plane at the origin, the current density it's simply: \mathbf{J}= \frac{I}{2\pi\sin\theta}\delta(\theta-\frac{\pi}{2})\frac{\delta(r-a)}{a}\hat{\phi}...
  8. faiziqb12

    Is Centripetal Acceleration Constant in Uniform Circular Motion?

    Homework Statement i was going through uniform circular but a confusion popped out of my head . as i have read before the Rutherford atomic model was only rejected due to the fact that electrons moving in circular orbits need to accelerate constantly to maintain a uniform speed but the...
  9. B

    Uniform Circular Motion of coffee cup

    Homework Statement Kim has her coffee cup on her car's dash when she takes a corner with radius 4 m and 20 km/h. What is the minimum coefficient of static friction which would allow the coffee cup to stay there without slipping? Homework Equations Can someone show me the steps in how they...
  10. K

    Circular motion in a magnetic field

    Homework Statement Small mass ##m## ball has a negative charge ##q## and is hanging on an inelastic string which has a length of ##l##. What is the smallest velocity that one need to impart on this ball for it to make one revolution? There is also a uniform magnetic field ##B## as shown in the...
  11. E

    Electric Field due to two circular line charges

    Homework Statement Two circular lines of charge are centred at the origin and lie on the xy plane. The inner loop has a radius of a and a total positive charge q. The outer loop has a radius of b and total negative charge -q. (a) Use Coulomb's Law to calculate the electric field on the z-axis...
  12. J-dizzal

    Planets and satellites, law of periods circular orbit.

    Homework Statement A 15 kg satellite has a circular orbit with a period of 4.4 h and a radius of 3.5 × 106 m around a planet of unknown mass. If the magnitude of the gravitational acceleration on the surface of the planet is 1.2 m/s2, what is the radius of the planet? Homework EquationsThe...
  13. metatrons

    Experimentally measure the degree of circular polarization

    Dear All: I have recently encountered a small question regarding the determination of the degree of circular polarization of light. In an optical experiment, we are trying to create a circular polarized light beam by passing a HeNe-laser through a linear polarizer and a quarter wave plate (in...
  14. Z

    Magnetic Field of Rotating Circular Ring

    Homework Statement Find the magnetic field at position z (z=0 in the plane of the ring) along the rotation axis for a circular ring of radius r, carrying a uniform linear charge density λ, and rotating about its axis with angular velocity ω. Homework Equations I=q/t ω=2πf f=1/period...
  15. G

    Uniform circular motion with friction

    I recently took an exam in my engineering mechanics class and passed the exam except for one question. I have been trying to solve this question after the fact and determine the solution, however neither I nor several engineering tutors have had any success. The professor refuses to give...
  16. G

    Direction of reaction force in a circular motion

    Homework Statement Thewheel is rotated in the anticlockwise direction...The correct reaction force is drawn using the blue pen . I don't understand why the reaction force isn't directed to the left ? which is drawn using the red colour ? IMO, the red colour should be correct because the...
  17. andyrk

    Tangential and Centripetal Acceleration in Circular Motion

    Why is there no component of tangential acceleration in uniform circular motion? I think its because when we apply the WE Theorem (Work-Energy Theorem) as follows: Work Done = ΔKE => F.S = 1/2*m*(vf2 - vi2), =>(ma).s = 1/2*m*(vf2 - vi2) => (ma).s = 1/2*m*(0) (since the speed remains constant in...
  18. Sarah00

    Circular Motion Equation homework

    Homework Statement Homework Equations Circular Motion Equation The Attempt at a Solution I solved the problem and got the result to be 6 m/s2 but it is not one of the answers. I was pretty sure of my solution. So, are all choices wrong? F = ma mg sin 37 = ma a = g sin 37 = 6.01 m/s2
  19. J-dizzal

    Uniform circular motion problem

    Homework Statement A police officer in hot pursuit drives her car through a circular turn of radius 356 m with a constant speed of 70.9 km/h. Her mass is 57.1 kg.What are (a) the magnitude and (b) the angle (relative to vertical) of the net force of the officer on the car seat? (Hint: Consider...
  20. J-dizzal

    Uniform circular motion of a particle problem

    Homework Statement A particle moves along a circular path over a horizontal xy coordinate system, at constant speed. At time t1 = 3.30 s, it is at point (5.10 m, 6.80 m) with velocity (3.90 m/s)## \hat j ## and acceleration in the positive x direction. At time t2 = 9.90 s, it has velocity...
  21. A

    A circular loop over a magnetic field directed outwards

    Homework Statement There is a counterclockwise current I in a circular loop of wire situated in an external magnetic field directed out of the page as shown. The effect of the forces that act on this current is to make the loop Select one: a. expand in size X b. contract in size c...
  22. J-dizzal

    Particle Uniform circular motion problem

    Homework Statement A particle moves along a circular path over a horizontal xy coordinate system, at constant speed. At time t1 = 3.30 s, it is at point (5.10 m, 6.80 m) with velocity (3.90 m/s) ## \hat j ##and acceleration in the positive x direction. At time t2 = 9.90 s, it has velocity...
  23. T

    Tension and Uniform Circular Motion (no r, ω, θ)

    Homework Statement A 0.020-kg mass is attached to a 1.2-m string and moves in a horizontal circle with a constant speed of 1.50 m/s, as shown in the figure. What is the measure of angle θ? What is given: m = 0.020kg v = 1.50 m/s L = 1.2 m Homework Equations Lengths L = 1.2m Lsinθ = r...
  24. G

    Vibration analysis - thin circular plate

    I'm moving on to a new area of focus at work and have found myself analysing a vibration issue. I've had the basics a BSME gets you at an accredited university (20 yrs ago), but am rusty to say the least. I'm looking for guidance on good reading materials to knock the rust off. My problem is...
  25. C

    Circular Aperture Diffraction, Angle of First Minimum

    Homework Statement A helium-neon laser ( ##\lambda =633nm##), is built with a glass tube of inside diameter 1.0mm. One mirror is partially transmitting to allow laser light out. From an optical perspective, the laser beam is a light wave that diffracts through a 1.0mm diameter circular...
  26. Mattman182

    Peak current flowing in a circular metal loop?

    Homework Statement Homework Equations I have some equations relating B to I but I don't really know if they are useful The Attempt at a Solution I actually don't even know where to begin on this, my notes are confusing and vague :(
  27. kostoglotov

    Uniform Circular Motion: a concept question

    Homework Statement A particle moving along a straight line can have nonzero acceleration even when its speed is zero (for instance, a ball in free fall at the top of its path). Can a particle moving in a circle have nonzero centripetal acceleration when its speed is zero? If so, give an...
  28. C

    Velocity of a Sphere Rolling in a Circular Bowl

    Homework Statement A solid sphere of mass M and radius a is released at vertical height y=R and rolls down a circular bowl without slipping, find an expression for the velocity of the sphere's center of mass at the bottom of the bowl. 2. Homework Equations ##I=I_c+Md^2## I=\frac {2} {5}...
  29. B

    What is the instantaneous velocity of an object moving uniformly in circles?

    Homework Statement An object is moving uniformly in circles with a radius of 5m and a frequency of 2 Hz. What is its instantaneous velocity? Homework Equations [/B]The Attempt at a Solution The problem i am dealing with is the frecuency. I am not here for an answer or to cheat. I am...
  30. Chaos_Theory

    Friction in non-uniform circular motion of a car

    Hi guys... So i searched the net for 2 whole days and found a couple of topics on how static friction is responsible for creating the force required to keep the body moving in a circle.. Friction points towards the center of the circle ONLY when the car is free wheeling i.e moving at a constant...
  31. T

    Conceptual Uniform Circular motion problem?

    Homework Statement This isn't a homework problem, but I was just thinking of the following question: Suppose that a merry go round spins with a constant speed (so its radially accelerating towards the center), and a man want to jump onto the merry go-round while its spinning. In what way...
  32. Glenboro

    How Do You Calculate the Moon's Speed and Acceleration in Its Orbit?

    Homework Statement The Moon’s nearly circular orbit about the Earth has a radius of about 385 000 km and a period T of 27.3 days. Determine the speed of the Moon. Determine the magnitude and direction of the Moon’s acceleration. Mark Criteria: A)determining the correct period of motion in...
  33. davidbenari

    Circular plate temperature distribution.

    Homework Statement The temperature distribution of a circ plate with radius ##a##, ##f(r,\theta,t)##, follows the diffusion equation ##\nabla^2f=\frac{1}{\alpha^2}\frac{\partial f}{\partial t}##, with a temperature of zero along the border. The initial temperature is...
  34. 1

    Uniform Circular Motion question

    1. The problem The answer is A. Homework Equations x = Acoswt y = Asinwt The Attempt at a Solution C is not correct because the x & y positions are in terms of sin & cos, so the acceleration can't be constant. D is not correct because x & y are oscillating in value. E is not correct because...
  35. C

    Potential of a point at the z axis of the circular ring?

    So i have a thin circular ring laying at the XoY plane, inner radius of the ring is a, outer is b, density of electricity is given by expression ρ=ρ0*b/r , where ρ0 is a constant and r ∈ (a,b). I have to find a potential of the point P with coordinates (0,0,z).I tried to do it two ways, but...
  36. moenste

    Mechanics. Circular motion and rotation

    Homework Statement An aeroplane loops the loop in a vertical circle of radius 200 m, with a speed of 40 m s^-1 at the top of the loop. The pilot has a mass of 80 kg. What is the tention in the strap holding him into his seat when he is at the top of the loop? Answer: 160 N. Homework...
  37. T

    Help on circular motion problem

    Homework Statement A ball of mass m is attached to a rigid vertical rod by means of two massless strings each a length L. Both strings are attached on the rod a vertical distance D apart. The rod, strings, and ball are rotated at some speed and both strings are taught. If the tension in the...
  38. pastoreerrante

    Scalar triple product invariance under circular shift proof

    Homework Statement Prove that for any three vectors ##\hat a, \hat b ## and ## \hat c##, ##\hat a \cdot (\hat b \times \hat c)## = ##(\hat a \times \hat b) \cdot \hat c ## Homework Equations [/B] ## \hat i \cdot \hat i = \hat j \cdot \hat j = \hat k \cdot \hat k = (1)(1)\cos(0) = 1 ## ##...
  39. cnh1995

    Induced current in a circular loop

    Hi friends..I'm struggling with an interesting puzzle...Suppose there is a circular conducting loop of radius 1/π cm, one half of which is made of a material with resistance 1Ω and the other half from a material with resistance 5Ω. If somehow, one managed to set up a changing magnetic field...
  40. H

    Exploring Circular Motion: Understanding the Behavior of a Conical Pendulum

    Such as the figure Why the string could not be horizontal when the rubber bungis moving in a horizontal circle? Only moving at conical pendulum? By the way, if tension is equal to weight(W), have any conclusion?
  41. Calpalned

    Relationship between harmonic and circular motions

    Homework Statement How is ##\frac{v}{v_M} = \frac{\sqrt{A^2 - x^2 }}{A}## derived? Homework Equations n/a The Attempt at a Solution I don't see a right angle in the picture anywhere, so I don't see how pythagorean's theorem is valid.
  42. Essence

    Using ampere's law for a circular loop

    Homework Statement Sorry to bother you guys, I've heard that Ampere's Law is either ineffective for calculating the B field due to a circular loop or needs some modification (I wasn't sure which). I'm trying to figure out why this doesn't work so I can get a better understanding of Ampere's...
  43. N

    Gear and gearbox design - circular pitch

    Hi everyone! Just joined the fórum after a lot of hours searching the web and Reading some books...I have one question, didn't found na answer to it...but let's give it a try ;) How can you determine the optimal circular pitch and in consequence the optimal diametral pitch of a gear (increasing...
  44. barryj

    Circular polarization and Read3D glasses

    I am trying to understand circular polarization and Real 3D glasses.I am sure that answers will lead to other questions. Question 1. Are Real 3D glasses merely quarter wave plates with each eye set at 90 deg angles to the other? or.. Question 2. Do Real 3D glasses consist of a linear...
  45. BilboBombadillo

    Help with circular velocity question (unit conversions?)

    Homework Statement Consider a satellite in circular low Mars orbit 300km above the planetary surface. R = 3396km M = 6.419 x 1023kg G = 6.674 x 10-11m3/kg/s2 Find the orbital velocity of the satellite (using the given values, I assume, as there is some inaccuracy in the real-life mass value...
  46. J

    Ray Tracing - Optics - Bend light with circular lenses

    Hey guys first time poster. I have written a 2D ray tracer in Mathematica. It's very basic, all it does is use Snell's law to trace ray refraction and very basic absorption. The set up is a central absorbing circle surrounded by circular lenses. The central circle is a perfect absorber, so if a...
  47. J

    Electromagnetic induction of a closed circular wire

    Homework Statement (See image) a closed circular wire A lies in the plane of the wire B in the circuit. Deduce the direction. Of the induced current in A when (A) the switch is closed (B) the switch is opened (C) the wire A is raised out of the plane of the paper. Homework EquationsThe...
  48. S

    Uniform Circular Motion and Projectile All-in-One

    Homework Statement \[/B] Joey spins a laptop then he releases it, at an angle. Assuming no wind resistance, the laptop (has a rubberized case) hits the concrete and drags across the concrete for 5.3 seconds. What is the coefficient of friction between the rubber and concrete and what distance...
  49. 0

    Why is there a force pointing towards the center of a circular trajectory?

    Homework Statement Explain why in circular motion there is a force pointing to the center of the trajectory. Use the momentum principle. Homework EquationsThe Attempt at a Solution So I choose two arbitrary points in the circular path and know that momentum and velocity are tangent to the...
  50. Calpalned

    Determine work in circular motion

    Homework Statement An object, moving along the circumference of a circle with radius ##R##, is acted upon by a force of constant magnitude F. The force is directed at all times at a ## 30 \degrees ## angle with respect to the tangent to the circle. Determine the work done by this force when...
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