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. E

    Is directional gas flow possible in a circular closed pipe system?

    If I have a series of pipes and containers (containing liquid) soldered together to create a circular path, and then heated at a particular point or multiple points, is it possible to somehow have the gas move in a particular direction without the gas every leaving the system? I'd prefer not to...
  2. T

    Uniform circular motion with constant upward velocity.

    Homework Statement It is common to see birds of prey rising upward on thermals. The paths they take may be spiral-like. You can model the spiral motion as uniform circular motion combined with a constant upward velocity. Assume a bird completes a circle of radius 6.00m every 5.00s and rises...
  3. P

    Circular Motion, Gravity, Muddy Wheel

    Homework Statement A car is moving with constant velocity v, and has wheels of radius R. The car drives over a clump of mud and the mud with mass m, and sticks to the wheel with an adhesive force of f perpendicular to the surface of wheel. At what angle (theta) does the piece of mud drop off...
  4. A

    Radius as a function of Uniform Circular Motion

    How exactly does radius affect centripetal acceleration? In one formula we have (a=v^2/r) which implies inversely proportional, while in the other we have (a=(w^2)*r) which implies directly proportional. I understand that increasing r increases velocity (v=w*r) which means the right answer is...
  5. C

    Circular Motion: angle that the airplane makes with horizon?

    Homework Statement The aeroplane is traveling at a speed of 75 m/s and the radius of the turning circle is 80 m. Homework Equations Calculate the angle which the airplane wings make the with horizontal during the turn. The Attempt at a Solution I tried but I couldn't get to the...
  6. Astrum

    Off center circular motion (polar coordinates)

    Homework Statement A particle moves with constant speed v around a circle of radius b. Find the velocity vector in polar coordinates using an origin lying on the circle. https://www.desmos.com/calculator/maj7t9ple1 Imagine the r starts at (0,0). Homework Equations \frac{d\vec{r}}{dt} =...
  7. Z

    Centripetal acceleration of a vehicle on banked circular arc

    Homework Statement A van is moving on a horizontal circular bend in the road of radius 75m. The bend is banked at arctan(1/3) to the horizontal. The maximum speed at which the van can be driven around the bend without slipping is 25m/s. Calculate the coefficient of friction between the road...
  8. F

    Circular Motion/Gravitational Acceleration Help Needed

    Hi, I am having problems with the following two problems: Homework Statement A 1.84kg ball is swung vertically from a 0.80m cord in uniform circular motion at a speed of 2.8m/s. What is the tension in the cord at the bottom of the ball's motion? Homework Equations I have tried using the...
  9. E

    Uniform Circular Motion - Finding Fc/Ft without mass

    Homework Statement A boy ties a rock to a 0.95 m string and swings it in a horizontal circle directly over his head so that it completes one revolution every 0.75 s. What is the tension in the string? So we know r and we can calculate V, but that's all I can deduce Homework Equations...
  10. H

    Uniform Circular Motion Derivation of Radial Acceleration

    Homework Statement I am trying to derive the formula a_r=\frac{v^2}{r} for uniform circular motion (for personal understanding, this is not an assignment). But am having some difficulty. I have seen other proofs, but I want to know why my approach is wrong. The Attempt at a Solution...
  11. A

    Circular motion x, y acceleration

    Can you tell me if my answers and sign are correct ? A car is traveling around a horizontal circular track with radius r = 250.0 m at a constant speed v = 18.0 m/s as shown. The angle θA = 19.0° above the x axis, and the angle θB = 60.0° below the x axis. What is the x component of the...
  12. A

    Relative and circular motion

    You are traveling on an airplane. The velocity of the plane with respect to the air is 120.0 m/s due east. The velocity of the air with respect to the ground is 43.0 m/s at an angle of 30° west of due north. 1.What is the speed of the plane with respect to the ground? I got 82.76 by doing...
  13. S

    What causes the normal force to increase in circular motion?

    Homework Statement In my physics book (Young and Freedman 12 edition), in the chapter about conservation of energy, it teaches me that I can use the theory of conservation of energy and discover the velocity at the bottom of a circular path, having the height of this circular path. I...
  14. Y

    Verify definition of circular polarization in Balanis.

    Attached is a scan of how Balanis define plane wave with circular polarization with Ey having a phase of +∏/2 respect to Ex component of the E field. I don't quite agree with the book. The second attachment is my derivation. The definition of CW or CCW is with respect to direction of...
  15. H

    Tension in a circular wire with force radiating outwards

    Homework Statement Let's say there's a uniform circular wire with radius r. There is a uniform force pushing outward from the center in all directions of the wire. This total force is 10N. What is the tension in the wire? Homework Equations N/A The Attempt at a Solution Let's say the...
  16. Z

    Dynamics of circular motion. Particle on the top of a circle

    Homework Statement A particle of mass M is on the top of a vertical circle without initial velocity. It starts to fall clockwise. Find the angle with respect to the origin, where the particle leaves the circle. Homework Equations v=ωXr The Attempt at a Solution I used two unitary...
  17. R

    Circular motion on a banked curve

    how can rcosθ in a banked road be equal to mg; since r is equal to normal reaction which is equal to mgcosθ. rcos is even smaller than r. so mg>mgcosθ mgcosθ=r r>rcosθ so mg>rcosθ then how can mg=rcos when banking in curved road?
  18. S

    Avoiding a Wall with Circular Motion: A Physics Exercise

    Should the driver apply brakes or turn the car in a circle of radius 'r' to avoid hitting the wall? This question is in the excercise of circular motion chapter. In this question I don't uderstand from where to start. Some help would be greatly appreciated.
  19. J

    Calculate the force on a circular surface

    Hi to everybody Homework Statement (The attachment has an image with this problem) A small probe P is gently forced against the circular surface with a vertical force F as shown. Determine the n- and t-components of this force as functions of the horizontal position s. Homework Equations...
  20. R

    Potential Difference of Hollow Circular Cylinder

    Homework Statement A hollow circular cylinder of radius a and length b, with open ends, has a total charge Q uniformly distributed over its surface. What is the difference in potential between a point on the axis at one end and the midpoint of the axis?Homework Equations U = kq/r The Attempt...
  21. I

    What Are the Unknown Variables in a Circular Arc Pilot Dynamics Problem?

    Homework Statement A pilot of mass 50 kg comes out of a vertical dive in a circular arc such that her upward acceleration is 6g. (a) What is the magnitude of the force exerted by the airplane seat on the pilot at the bottom of the arc? (b) If the speed of the plane is 390 km/h, what...
  22. B

    Relative Circular Speed given radius and time

    Homework Statement What is the speed of the object (a bird) relative to the ground? We are given that a bird is flying in a spiraling path and rising on a thermal, making circles with a radius of 6m every 5s and rising strait up at a velocity of 3m/s.Homework Equations V=d/t C=2πr=d The...
  23. Q

    Circular Motion (ratio of velocities)

    Homework Statement Two small planets are moving in circular orbits around the same star. If the radius of the orbit of planet A is 4 times the radius of the orbit of planet B, find the ratio of their speeds vA/vB. Homework Equations Not really sure but v=omega*r a(centripetal)=v^2/r...
  24. A

    I'm writing a program that simulates circular

    I'm writing a program that simulates circular "particles" in 2d space. I'm at the collision handling part. I've already corrected their positions when an overlap occurs. So, my question is, how do I determine the angle of each particle's velocity after the collision? I have the position and...
  25. T

    Finding the natural frequency of a cylinder oscillating on a circular surface

    Homework Statement Here is the problem with my 3 attempts: 1. Alright, so the first attempt, I did not take into account the rotation of the cylinder ωc so I think it is wrong. But it seems to make sense because the whole cylinder rotates about O, so if I find that energy using parallel...
  26. D

    MHB Circular Membrane: Solving $u_{tt} = c^2\nabla^2u$ with Bessel's Equation

    $u_{tt} = c^2\nabla^2u$ where $\nabla^2 = \frac{1}{r}\frac{\partial }{\partial r}\left(r\frac{\partial}{\partial r}\right) + \frac{1}{r^2}\frac{\partial^2}{\partial\theta^2}$. Suppose $u(r,\theta,t) = G(r,\theta)e^{i\omega t}$. Then $$ -\omega^2Ge^{i\omega t} = c^2\nabla^2Ge^{i\omega t} $$ which...
  27. J

    Tension in vertical circular motion

    Homework Statement If you are spinning an object of mass 3.25 kg on a 0.8 m long chain at 20 rpm (vertical cirular motion), a) what is the tension at the top b) 43° from the top and c) at the bottom?Homework Equations String tension: T = Fc - mg cosθ Tension at top: T = (mv^2/r) - mg Tension at...
  28. L

    Simple magnetic field circular motion problem

    There's basically a beam of protons moving in the x-y plane, 30 degree from the +x-axis. The magnetic field is oriented in the +z-axis. So would the particle's motion be circular or helical? I say helical, because the velocity isn't completely perpendicular. Is this correct?
  29. U

    Circular Motion Dynamics. Car traveling in vertical circle

    Homework Statement A small car with mass .800 kg travels at a constant speed of 12m/s on the inside of a track that is a vertical circle with radius 5.0m. If the normal force exerted by the track on the car when it is at the top of the track is 6.00N, what is the normal force at the bottom of...
  30. A

    Normal force in circular motion

    Hi, Suppose we have a fellow on a ferris wheel. Would the normal force be greater on the top or at the bottom of the ferris wheel? I'm thinking that it would be greater at the top, or am I wrong? Thanks,
  31. V

    Density word problem A 300 kg meterorite is in circular motion orbiting a far

    Homework Statement So my professor gave me this formula GMplanet = (v^2 x d)/a to solve for the question and told me that m/v = density. I was told then to multiply the end result of m by 1000 and v by 1,000,000 to get the answer. I am given all the knowns except the acceleration. How do i...
  32. P

    Circular Motion - RPM and Radius question

    Homework Statement A manufacturer of CD-ROM drives claims that the player can spin the disc as frequently as 1200 revolutions per minute. a. If spinning at this rate, what is the speed of the outer row of data on the disc; this row is located 5.6 cm from the center of the disc? b. What is the...
  33. P

    Energy combined with Circular Motion

    Homework Statement Consider a small box of mass m sitting on a wedge with an angle θ and fixed to a spring with a spring constant k and a length in a non-stretched state L. The wedge rotates with an angular velocity ω around the vertical axis. Find the equilibrium position of the box...
  34. fluidistic

    Circular membrane, PDE, separation of variables, coefficients.

    Homework Statement I must find the oscillations of a circular membrane (drum-like). 1)With the boundary condition that the membrane is fixed at r=a. 2)That the membrane is free. Homework Equations The wave equation \frac{\partial ^2 u }{\partial t^2 } - c^2 \triangle u =0...
  35. V

    Algebra II Trigonometry Circular Functions

    Homework Statement Find the exact values of the six trigonometric function of the given number. If a function is undefined for the number, say so. 11\pi/6Homework Equations The Attempt at a Solution The way I did it was to turn it into radians by simply doing the math... 5.76 radians Then...
  36. P

    Circular motion, unbalanced-balanced forces

    Question 1 A box of mass 5.8 kg is pulled to the right with a horizontal force of 8.2 N. If the box moves to the right with constant velocity of 2.66 m/s, what is the frictional force acting on the box? Question 3 A person pulls on a 41 kg table with a 215 N force acting at an angle of...
  37. S

    How Does Chiral Substance Affect the Propagation and Refraction of Light?

    When a substance has coefficient of refraction that depends on direction, a single ray of unpolarized light incident on its surface normally splits in 2 rays - no fewer except in case of specific directions where the 2 coincide, but also no more - which have different, linear, polarization...
  38. B

    Resistivity measurements of a circular shaped sample

    Hai, I am doing my masters degree in physics. can somebody help me in which formula to use for calculating resistivity of a sample of circular shape using two probe measurements, which should include thickness and correction factor also. Thank You!
  39. L

    What is the maximum height reached by two masses after an elastic collision?

    Homework Statement a 6 kg, originally held at rest in position 1 as shown in the diagram below, slides down a frictionless quadrant of a verticle circle of radius 15 m. It then collides elastically with another 16 kg mass at rest at position 2. They bounce off each other and move on the...
  40. M

    Converting Linear Accelerator To Circular One

    Hi guys , Suppose there is a circular accelerator has the same inner structure of a linear accelerator in terms of the rings of acceleration ... The angular frequency of accelerated particles is : ω = qB/m = 2πf , and this is also the supplied current frequency ... The question is ...
  41. I

    Circular profile in compression (material mechanics)

    Homework Statement A circular profile with radius r is subjected to opposing compressive forces Fc in the x and y directions as show. If the material has compressive strength sigma_c = 2000MPA, at what compressive force Fc will the profile experience failure? Homework Equations...
  42. T

    Universal Gravity Circular Orbit

    Homework Statement What is the radius of a circular orbit about the Earth where the acceleration is 0.1g? Homework Equations g=9.8m/s^2 F=(Gmm)/r^2 Radius of Earth= 6.38x103 km Mass of Earth= 5.98x10^24 m/s The Attempt at a Solution I said 1/(2^x)=1/10 then did log2(10)=x and solved...
  43. A

    The moment of inertia of circular sector

    Hello how can I find the moment of inertia of a circular sector about the X axis , which the sector is symmetrical about , with -θ down and θ above ?! I_{x} = ∫y^{2} dA = ∫y^{2} *y *dx Or =∫∫ y^{2} dy dx I don't know how to put the limits of integration , I turned it to polar...
  44. M

    Magnitude of acceleration in circular motion

    Homework Statement A ferris wheel with radius 14.0m is turning about a horizontal axis through its center. The linear speed of a passenger on the rim is constand and equal to 7.69m/s. What is the magnitude of the passenger's acceleration as she passes through the lowest point in her circular...
  45. S

    Circular Motion (high school level)

    Homework Statement The carnival ride shown in Figure 7-18 has a 2.0 m radius and rotates once each .90 s a. Find the speed of the rider. b. Find the centripetal acceleration of the rider. c. What produces this acceleration? SOLUTIONS PROVIDED: a. 141 b. 98 c. --Explain-- Homework Equations...
  46. P

    Circular Movement: Exploring Particle Motion

    Hello, If the position of a particle w.r.t time is given as X=Acos(t)exp(-at), and Y=Asin(t)exp(-at), then it is pretty clear that the particle is moving in concentric circles around the origin with decreasing radius. Is anything else ought to be stated in order to describe the motion of the...
  47. P

    Energy inside a cyclotron, and the frequency of circular motion

    Homework Statement One of the first cyclotrons, built in 1932, has D-s with a diameter of 28 cm, and its magnet was capable of producing magnetic field of 1.4 T. What is the maximal energy of the protons accelerated by this cyclotron? What is the frequency of the circular motion?Homework...
  48. U

    Circular Plate with eccentric hole

    Hi everybody, I'm looking for a way to determine the maximum moment of a uniformly loaded circular plate (diameter = 10") with eccentric circular hole (diameter = 4"). The plate is clamped at outer edge and free at inner edge. The ultimate objectif is to determine the minimum thickness of...
  49. W

    Uniform Circular Motion of a race car

    Homework Statement A 990-kg race car can drive around an unbanked turn at a maximum speed of 42 m/s without slipping. The turn has a radius of 140 m. Air flowing over the car's wing exerts a downward-pointing force (called the downforce) of 12000 N on the car. (a) What is the coefficient of...
  50. D

    Distance traveled in a circular motion

    Homework Statement A car starts from rest and accelerates around a flat curve of radius R = 31.7 m. The tangential component of the car’s acceleration remains constant at at = 2.97 m/s2, while the centripetal acceleration increases to keep the car on the curve as long as possible. The...
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