Circular Definition and 999 Threads

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. C

    How Does Circular Polarization Arise in String Wave Motion?

    Homework Statement The horizontal component of a wave is in the y-direction, and the vertical component is in the x-direction. If the horizontal and vertical components of a wave on a string have the same amplitude and are 90 degrees out of phase (say δv=0 and δh= 90°). At a fixed point z...
  2. C

    Force Analysis in Circular Pipe: How to Approach Vertical Force Balance?

    "Consider a fully developed laminar flow in a circular pipe, perform force analysis on an element of the real fluid." I've just started this type of question, and I'm a bit confused about where to go from here: I've managed to do a force balance horizontally to show that the partial derivative...
  3. R

    Uniform circular motion - finding velocity

    Homework Statement Homework Equations radial acceleration = v^2/R The Attempt at a Solution I'm unsure if we have to mention the tension of the cable, but I'm guessing L2 will suffice? Correct me if I am wrong. Anyways, I drew the diagram from a side view (kind of like a circular pendulum)...
  4. K

    Circular Motion and Energy Calculations

    Homework Statement A) An object moving along the x-axis is acted upon by a force Fx that varies with position as shown. How much work is done by this force as the object moves from x = 2 m to x = 8 m? B) A 50-kg child riding a Ferris wheel (radius of wheel R = 10 m) travels in a vertical...
  5. P

    Circular motion and acceleration

    If you are twirling a rock around your head with a rope (assuming it is uniform circular motion), then the only acceleration that is acting is radial. So if you take a look at the rock at any given instant, its velocity is perpendicular to its acceleration. My question is, why does the rock not...
  6. Dietrichw

    Projectile and Uniform Circular Motion

    Homework Statement An object is launched horizontally from the highest peak on the Moon's surface. Calculate (a) the launch speed required so that the object travels completely around the Moon and returns to its original position, and (b) the time required to return to the launch point. Assume...
  7. quaticle

    Finding electric flux through the circular cap of a sphere

    Homework Statement A sphere of radius R = 1.40 m surrounds a particle with charge Q = 42.0 μC located at its center as shown in the figure below. Find the electric flux through a circular cap of half-angle θ = 28.0°. Homework Equations Φ = ∫E⋅dA E = (kq)/r2 A = πa2 where a = rsin(θ) --> from...
  8. Priyadarshini

    Circular Motion and resultant force

    Homework Statement Homework Equations F= mv^2/r v = angular vel* r The Attempt at a Solution resultant force= ma-frictional force = mv^2/r - mg*meu = (angular vel)^2mx - mg*meu But then how do I get the angular speed when I don;2 know the resultant...
  9. teroenza

    Approximating H Wavefunction Circular State for Large n

    1. Homework Statement We are studying circular states of the hydrogen atom (states where the l quantum number is = n-1). We are asked to evaluate \langle \Psi_{n,n-1,n-1}| r_{n,l=n-1}|\Psi_{n,n-1,n-1}\rangle . The wave function is that of the hydrogen atom, and the thing we are taking the...
  10. NihalRi

    Circular motion , the loop the loop

    Homework Statement The loop-the-loop machine has radius R of 18m (a) What is the minimum speed at which a cart must travel so that it will safety loop the loop (b) what will the speed at the top be in this case Homework Equations Centipetal force = m*v^2/r Kinetic and potential energies =...
  11. M

    Finding Volumes of Sphere & Circular Cone: Alpha from 0 to Pi

    Use an appropriate volume integral to find an expression for the volume enclosed between a sphere of radius 1 centered on the origin and a circular cone of half-angle alpha with its vertex at the origin. Show that in the limits where alpha = 0 and alpha = pi that your expression gives the...
  12. A

    What is the self inductance of a circular loop of wire?

    If current I passes through a circular loop of radius R,then what will be the self inductance of that loop? (calculating flux through the loop leads to calculating magnetic field at every point inside the loop which is an elliptic integral.)
  13. RoboNerd

    Conceptual Question on acceleration and circular motion

    Homework Statement If a roller coaster car enters the circular-loop portion of the ride and navigates it successfully, then the net force on the car at its topmost point is straight down. Then why does not the car fall down? So I am having issues understanding my textbook's solution to the...
  14. M

    Roller coaster - uniform circular motion

    Hi, I have been studying up on circular motion in the vertical plane and I am happy with all the math/theory that I have read explaining the normal force and weight force and the feeling of being "heavier" and "lighter". My question is about the top of the hill/ride, The forces acting on you at...
  15. H

    Find frequency response and circular frequency

    Homework Statement We are given that system of 1st grade 1/2 * dy(t)/dt + y(t) = x(t) 1) We need to find frequency response { H(w) } 2) We need to find circular frequency -3dB 3) We need to find the absolute value of H(w) in dB for frequency f = 3/π Hz 2. Homework Equations (log is always...
  16. K

    How Does Pulling the String Affect the Speed of a Ball in Circular Motion?

    Homework Statement Ball of mass=m on the frictionless table is connected to a string that passes in hole that is in table. The ball is set into a circular motion on a circle of radius = R. If the string pulled from the bottom, withe the force F, so that the radius of motion of ball would...
  17. D

    Calculating Revolutions for a Spinning Wheel | Circular Motion Problem

    Homework Statement A wheel spins at an angular speed of 2.50 rad/s for a total of 30.0s. How many complete revolutions will the wheel make during this time? A) 31.4 rev B) 19.3 rev C) 11.9 rev D) 75.0 rev Homework Equations W=Wo+(alpha)(t) θ=θo+Wot+1/2(alpha)t^2 W^2=Wo^2+2(alpha)(θ-θo) The...
  18. G

    Wave Equation for Circular Waves

    What's the solution to the wave equation for circular waves on a two-dimensional membrane? The waves have a constant wavelength throughout. For spherical waves, you have to multiply the amplitude by 1/r. I tried 1/√r for circular waves but it didn't work. :blushing:
  19. C

    How to Calculate Average Velocity on a Circular Track?

    Homework Statement A car travels on a circular track at 20m/s. The track has a circumference of 2.0km. What is the average velocity of the car over one lap? Homework EquationsThe Attempt at a Solution Since the car is traveling at a constant speed of 20m/s, wouldn't the average velocity be...
  20. A

    Direction of friction when a body moves in a circular track?

    please explain why? Take 2 cases,and explain how is the direction of friction different in these 2 cases. CASE 1:uniform circular motion CASE 2:non uniform circular motion my thought was,friction opposes relative motion,so it must be tangential to the particle at each and every point. i very...
  21. T

    Why is induced electric field circular?

    Time-varying magnetic field makes electric field circular(or close loop). I am asking the reason why it is circular or close loop shape?
  22. J

    Is the train in the circular track paradox similar to the barn/pole paradox?

    This is a follow on to a prior thread, Another circular twin paradox Consider a train of proper length 100 at rest in an inertial ground frame. It is accelerated Born rigidly to the right on a straight track to 0.6c in the ground frame, after which is still has proper length 100 but has now...
  23. Mr Davis 97

    Difference between circular motion and rotational motion

    I don't really understand the difference between uniform circular motion and rotational motion. I know that uniform circular motion deals with a body that is orbiting around a central point, with a centripetal force that is causing it to move in a circle. I know that rotational motion uses...
  24. K

    Finding angular velocity -- circular motion

    Homework Statement A mass m1= 0.200 kg is tied to a string with enough slack to swing around someone's head with a radius of 0.500 meters. What angular velocity must m1 have in order to hold up a mass m2 hanging from the other end of the string if m2 is 0.300 kg?Homework Equations ac= v^2/r...
  25. M

    Newton's second law : circular motion

    Homework Statement A car travels along the perimeter of a vertical circle (radius = 0.25 km) at a constant speed of 30 m/s. What is the magnitude of the resultant force on the 60-kg driver of the car at the lowest point on this circular path? Question options: 1) 0.37 kN 2) 0.80 kN 3) 0.22 kN...
  26. M

    Calculus of variations with circular boundary conditions

    The Euler-Lagrange equations give a necessary condition for the action be extremal given some lagrangian which depends on some function to be varied over. The basic form assumes fixed endpoints for the function to be varied over, but we can extend to cases in which one or both endpoints are free...
  27. J

    Does the Circular Twin Paradox Challenge Our Understanding of Time Dilation?

    Here is a scenario in which two twins age at different rates even though both always have the same speed.Consider a train track that includes a circular segment with ground circumference minutely greater than 80. Two twins are on a train with synchronized watches (Frank at the front and Reba at...
  28. Y

    Two satellites A and B move around earth in a circular orbit

    Two satellites A and B move around Earth in a circular orbit. The mass of B is twice the mass of A then I agree that kinetic energy of B is greater than that of A. But what I couldn't understand was that why are speeds of A and B equal as given in the book. Shouldn't they differ according to the...
  29. C

    Circular Motion Question searching for Centripetal force

    Homework Statement A 50 g weight is swung in a circle on the end of a 90 cm long string at the speed of 5.9 m/s, what is centripetal force? [1.9 N] Homework Equations Vc = (2πr)\T |a| = v^2/r Fc = T-Fg (not sure if T is force of tension or period, my teacher,incorrectly,uses it...
  30. S

    How to Find Magnetic Field Components of a Circular Loop?

    Homework Statement A circular loop of radius R is on the xy plane and the center is at the origin, the current is flowing in a counter-clockwise manner. a) Let Q=(a,0,a) be a point such that a>>R. Find Br and Bθ at Q. b) Let Q=(ha,0,0) be a point on the x-axis such that h<1. Find the vector...
  31. gracy

    Equivalent capacitance, circular arrangement

    Mentor's note: Post moved to new thread since it's a new problem. One more problem Homework Statement Find the equivalent capacitance between A and B. Homework Equations The Attempt at a Solution I think all the Capacitors are in series but according to my book only three capacitors are in...
  32. S

    Circular Motion Seesaw Balance Question

    Homework Statement Describe the relationship between the resulting torque from each scenario using the torque equation. Question this question is addressing- Using the bricks from the materials on the right, create and record 10 different combinations of two unequal masses that result in a...
  33. B

    Various locations during a vertical circular motion

    For a vertical circular motion, its standard to solve for tension at the 4 common points on the circle (North, South, East, West) My question is, is it possible to solve for tension at other locations? Example :https://www.dropbox.com/s/c4q1sprphol2tzb/20151127_020345.jpg?dl=0 Can i resolve...
  34. S

    Why is tension greatest at bottom in circular motion?

    Hi. I am having some difficulty with circular motion.An object is spun vertically on a rope a) when would the string be most likely to break? The object would most likely to break when it has the most tension, so at the bottom of the circle it is Ft-Fg=Mv^2/r which is (Ft=Mv^2/r + Fg) while the...
  35. A

    Finding Tension in Horizontal circular motion with friction

    Homework Statement A car of mass (m) is attached to a cable of length (L) to a rotating pole. The car will speed up and travel in a circle. If the maximum speed of the car is vmax, what should the minimum strength of the cable connecting the car to the pole be? Note the surface is not...
  36. S

    Uniform Circular Motion and Centripetal acceleration

    Homework Statement For a scene in a movie, a stunt driver drives a 1.20✕ 103 kg pickup truck with a length of 4.65 m around a circular curve with a radius of curvature of 0.333 km (Fig. 7.29). The truck is to curve off the road, jump across a gully 10.0 m wide, and land on the other side 2.96 m...
  37. a lone fishy

    Intro to Uniform Circular Motion/Centripetal Acceleration

    Hi everyone, 1. Homework Statement Homework Equations 1) centripetal acceleration = v^2 / R 2) centripetal acceleration = 4 pi^2 R / T^2 3) average velocity = displacement / time[/B]The Attempt at a Solution For #1a I first found the displacement of A to B. And then divided that by...
  38. C

    Circular Motion: Solving for Velocity using Vector Cross Product

    Homework Statement http://i.imgur.com/Nbg3Nrc.jpg pic of question Homework Equations v = wr, s=rtheta t=1/f etc The Attempt at a Solution i did a, got 504 radpersec and then did b, r = 1.3sin40 i - 1.3cos40 j + 0 k but I'm not sure if I'm doing it right. can anyone help me and point me in...
  39. D

    Impact velocity after exiting circular motion

    Hello, i want to determine the velocity with which an object moves after it has departed a rotating disk. In my problem there is a disk rotating with the angular speed w. On this disk there is a drilling in which a mass m is positioned. In case the thread in the drilling fails i need to...
  40. 1

    A way to plastically flip a circular polariser?

    hi, I'm currently talking about light, and I'm trying to find out if there is a material or a method that can flip a polariser's polarisation... ie, if i apply a current, then this crystal changed from a clockwize polariser to an anti-clockwize polariser, and it is either a plastic or elastic...
  41. I

    Quantum Tunneling from Bent Circular Wire

    Homework Statement The electron enters a straight pipe of circular cross section (radius r). The tube is bent at a radius R≫r by the angle α and then is aligned back again. Find the probability that the electron will jump out Homework Equations Tunneling probability in WKB approximation. The...
  42. uselesslemma

    Force on a Circular Loop Due to an Infinite Wire

    Homework Statement A long straight wire carrying a constant current I1 and a circular wire loop carrying a constant current I2 lie in a plane. The radius of the loop is R, and its center is located at distance D from the straight wire. What is the magnetic force exerted on the loop by the...
  43. G

    Finding the area of a circular strip

    http://edugen.wileyplus.com/edugen/courses/crs7165/art/qb/qu/c29/pict_29_93.gif if I wanted to find the area of the outer circular strip, I know I would just take the area of the composite and subtract out the inner radius. (i.e. pi(a^2)-pi(b^2)). However why can't I use...
  44. T

    Uniform Circular Motion for rubber stopper

    Homework Statement Picture- https://flic.kr/p/zi1ays The rubber stopper will be spun at a constant speed in a horizontal circle. The hanging mass is only in contact with the string.[/B] A) For the rubber stopper, state the forces and what they are exerted by and on B) Does the net force have...
  45. Chrono G. Xay

    Attempting to Predict Tension on a Circular Membrane

    I have been wanting to write an equation which predicts the tension on a circular membrane (AKA drumhead). However, I'm not sure that my answer is on the right kind of track, if it's even correct. As for the procedures I took, first I started with the equation for tension on a string, which I...
  46. N

    Solving for Skid: Exploring Kinetic Friction on a Circular Track

    Homework Statement This isn't a problem from a textbook or homework but just a general question. Say there's a car traveling in a circle and that the track has some coefficient of kinetic friction µ. What would make the car skid? Homework EquationsThe Attempt at a Solution I'm thinking that...
  47. K

    Two dimensional movements and circular motion

    Homework Statement Hello, i got three different assignments i need help with right now, my teacher overestimated me and my physics skills, so I'm kind of lost on these three: (i'm european so i work with meters) 1: A planets radius is 10 000 km. the gravitationalacceleration is g0 = 15 m/s^2...
  48. H

    How Do Rollercoasters Use Circular Motion and Acceleration?

    Homework Statement A rollercoaster consists of a 45 degree slope that is 100 m long followed by two loops which have radii of 40 m and 20 m respectively. If the rollercoaster accelerates down the initial slope due to gravity, determine: a. The acceleration of the rollercoaster down the 45...
  49. N

    Acceleration in non-uniform circular motion

    In a non-uniform circular motion (for example a pendulum), can the centripetal/radial acceleration ever be 0? Likewise, can the tangential acceleration ever be 0? The centripetal acceleration occurs because of the centripetal force, which causes the body (in the example of the pendulum, the...
  50. N

    Acceleration in non-uniform circular motion

    In a non-uniform circular motion (for example a pendulum), can the centripetal/radial acceleration ever be 0? Likewise, can the tangential acceleration ever be 0? The centripetal acceleration occurs because of the centripetal force, which causes the body (in the example of the pendulum, the...
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