What is Conservation: Definition and 999 Discussions

Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an interdisciplinary subject drawing on natural and social sciences, and the practice of natural resource management.The conservation ethic is based on the findings of conservation biology.

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  1. amjad-sh

    Diffraction of light and conservation of energy.

    Suppose that we shined a source of light on a wall with infinitismal small opening. As the opening is infinitismly small, only one ray of light will pass through the opening ( suppose it has an intensity ##I_0##) and this ray of light will diffract into an infinite number of light rays with the...
  2. T

    Resonance vs. Conservation of Energy

    I can solve the equation for a damped oscillator with a forcing function. I can then plot the Kinetic and Potential Energy. They will be out of phase, of course (KE peaking when PE is zero, and vice versa) And we know that when the input frequency is close to the natural frequency, the system...
  3. mcastillo356

    First law of Thermodynamics and energy conservation

    Hi PF! I don't understand the sentence: on one side says the energy is preserved, and, at the end, the total energy of the system will change if ##W## or ##Q## is added: ##\Delta{U}=Q+W##. Greetings!
  4. N

    I Conservation of energy in Everett's MWI

    The question seems similar to the one asked here, https://www.physicsforums.com/threads/energy-in-everetts-many-worlds-interpretation.966266/ but since there didn't seem to be an answer I am asking it again in a slightly different form. I was watching a youtube video where Sean Carroll...
  5. E

    Conservation of Energy Problem (Power)

    Hello there, I was trying to solve this problem. I have no problem with part A and C. But in part B, my guidebook arrived with different answer. Can anybody point out what my mistake is? I am using the same method as the elevator motor problem which states : "A 650-kg elevator starts from rest...
  6. T

    Conservation of Mechanical Energy

    Okay For a this is what I did. a. I'm confused about B. I understand that it has something to do with the Conservation of Mechanical Energy, but I don't exactly know what to do.
  7. wcjy

    Rotational dynamics and the conservation of energy

    I = Icm + mr^2 I = 0.5 mr^2 + mr^2 I= 3/2 mr^2 By COE, mgh = 0.5(3/2 mr^2)(w^2) g(2r) = 3/4(r^2)(w^2) 8g/3 = rw^2 = v^2 / r v = sqrt( 8gr/3) v=0.511m/s ans: v=0.79m/s
  8. A

    Conservation of Angular Mometum for a Car/Earth System

    See attached. You can see how the car as a whole conserves angular momentum with earth. Car pushes back, Earth moves back and rotates, car accelerates forward. https://www.animations.physics.unsw.edu.au/jw/momentum.html However, the ground puts a friction force on the front non-driving wheel...
  9. J

    Does density of a medium affect the conservation of momentum?

    Hi all, If a body has a given initial momentum and then travels through a continuously less dense medium would it's velocity increase to conserve momentum? Thanks Jerry
  10. kuruman

    Insights Why Bother Teaching Mechanical Energy Conservation?

    Continue reading...
  11. wcjy

    Kinematics, Conservation of energy, momentum

    m1 + m2 = 8 COE 0.5(m1)(u1)^2 + (m1)(g)(30) + 0.5(m2)(u2)^2 + (m2)(g)(30) = 0.5(m1)(v1)^2 + 0.5(m2)(v2)^2 + (m2)(g)(16) Can you check if my eqn is correct? And can you advise what to do after this? I wanted to do COLM but i don't know what is the initial part.
  12. wcjy

    Momentum and Conservation of energy

    When A hits B, COLM mV = -mVa + 2mVb V = 2Vb - Va COKE 0.5mv^2 = 0.5mVa^2 + 0.5(2m)Vb^2 V^2 = Va^2 + 2Vb^2 When B hits C COLM 2mVb=4mVc Vc = 0.5Vb COE 0.5(2m)Vb^2 = 0.5kx^2 +0.5(4m)Vc^2 sub Vc = 0.5b mVb^2 = KX^2 After that I am stuck, cause i can't find V in terms of Vb only
  13. A

    Conservation of Energy Along an Incline with Friction

    There are two nonconservative forces in this situation, the work done by the person and the work done by friction - they are the only sources of work that change the total mechanical energy of the mass-Earth system. The initial energy (assuming gravitational potential energy is initially 0) is...
  14. P

    Energy Conservation between mechanical and electrical

    I am not sure if i can explain my question properly. I am studying the Generators section in the magnetism chapter. As i mentioned the statement "The rate at which work is done is exactly equal to the rate at which energy is dissipated in the resistance". When the term dissipated is used does it...
  15. M

    Conservation law for FRW metric

    My attempt: Realize we can work in whatever coordinate system we want, therefore we might as well work in the rest frame of the fluid. In this case ##u^a=(c,\vec{0})##. The conservation law reads ##\nabla^a T_{ab}=0##. Let us pick the Levi-Civita connection so that we don't have to worry about...
  16. Haorong Wu

    I Does vacuum excitation violate the conservation of energy?

    Hi, there. I am reading the article Relativistic quantum optics: The relativistic invariance of the light-matter interaction models by Eduardo Martin-Martinez el al (2018). Here he calculate the transition probability of a vacuum excitation for a detector. Suppose there is a lab where the...
  17. T

    Can the charge conservation law be derived from Maxwell equations?

    From Maxwell's equations \partial_\nu F^{\mu\nu}=J^{\mu}, one can derive charge conservation. The derivation is 0\equiv \partial_\mu \partial_\nu F^{\mu\nu}= \partial_\mu J^{\mu} { \Rightarrow}\partial_\mu J^{\mu}=0. However, a circular reasoning exists in it. For the sake of better...
  18. burian

    Application of momentum conservation in inelastic collisions

    So, what I did was suppose the mass of ramp is $ M_r$ and let velocity at B of block be v, then, after inellastic collsion both bodies v' velocity at B , $$M\vec{v}= M_r \vec{v'}+ M \vec{v'}$$ or, $$ \frac{M}{M +M_r} \vec{v}= \vec{v'}$$ Now, Suppose I take the limit as mass of ramp goes to...
  19. bsharvy

    Energy Conservation and the Dragons (Game of Thrones)

    I thought I'd calculate how much heat was required to melt the Iron Throne, and then multiply that by the number of flame-gushes during the sack of Kings Landing, to get a total amount of energy expended. Then I'd convert that to calories and use the average number of calories per goat to...
  20. E

    Work & energy VS conservation of angular momentum

    Summary:: Would energy method give us a different answer from conservation of angular momentum? Hello, I do not know how to type equations here. So, I typed my question in Word and attached it here. Please see photos. Note: This question is not a homework. I did not find it in textbooks or...
  21. madafo3435

    Energy conservation .... contradiction?

    In b). Since the force T is perpendicular to the trajectory of the mass m, T does not perform any work on m, therefore the translational mechanical energy is conserved, from which I deduce that the initial speed is equal to the final speed, moreover, the speed is constant. Now, when analyzing...
  22. Vivek98phyboy

    What am I Missing? Solving Conservation of Energy

    By solving conservation of energy, I was able to find the linear velocity which is [10g(H-R-Rsin(theta))/7]^½ and by differentiating this with respect to "t", I arrived at the tangential acceleration value of -(5gcos(theta))/7 and found it to be in agreement with the solution provided in the...
  23. A

    Energy conservation of metallic balls

    I did energy conservation, considering that the final velocity of the largest mass would be zero and I used moment conservation. But I am not finding the answer . Where I maked a mistake?
  24. Prabs3257

    Understanding Momentum Conservation in Simple Harmonic Motion

    I first got the velocity of the combined mass with conservation of momentum and as it was in the mean position the velocity can be written as v = wA ( w= angular frequency , A = amplitude ) as we have to take it back to natural length i put A as the initial extension but i am getting a wrong ans...
  25. Simon Bridge

    A Conservation of angular momentum in positron-electron annihilation

    Pretty much in a nutshell... fielded a question about how spin affects electron positron annihilation... ie do the spins have to be opposite in order to conserve angular momentum for two-photon annihilation to happen? Intuitively I figured that looks reasonable ... but decided to check, and...
  26. Saptarshi Sarkar

    Conservation of angular momentum and rotational kinetic energy

    I first tried to get the solution by conserving the rotational kinetic energy and got ##\omega'=\frac2{\sqrt5} \omega##. But, it was not the correct answer. Next I tried by conserving the angular momentum and got ##\omega'=\frac 45 \omega##, which is the correct answer. Why is the rotational...
  27. VVS2000

    Conservation of relativistic momentum

  28. T

    Conservation of energy problem: Two masses, a pulley and an incline

    If M moves ##x## along the plane, her height variation in ##x \cos(\alpha)##, and, but I don't know how to find the variation of the height of ##m##
  29. P

    Conservation of momentum and energy problem

    In an elastic collision, a 400-kg bumper car collides directly from behind with a second, identical bumper car that is traveling in the same direction. The initial speed of the leading bumper car is 5.60 m/s and that of the trailing car is 6.00 m/s. Assuming that the mass of the drivers is...
  30. AlonZ

    Mechanics- Conservation of energy

    My, supposedly rational thought is that if the pendulum will drop from a height higher than the top of the loop's height, by the law of conservation of energy, it'll have enough velocity to complete the loop. The teacher's final result shows a different approach. Am I right? Wrong? Thanks
  31. anuttarasammyak

    Energy transfer and conservation cases for pendulum motion and EM wave

    Let me ask a very primitive question. To and fro motion of pendulum under gravity tells us potential energy + kinetic energy = const. At the top points potential energy: max kinetic energy :0 At the bottom point potential energy: 0 kinetic energy :max EM wave is usually illustrated as...
  32. D

    Relativistic energy and momentum conservation

    Summary:: this is what I've done so far... i don't think it works since i believe the information given is not even enough. the formula I've used are 1. relativistic total energy = rest mass energy + kinetic energy (line 1, 3) 2. conservation of energy (line 4, 7, 8, 9) 3. conservation of...
  33. T

    Child going down a water slide (potential energy and energy conservation)

    Vf = ? y = ? ME = mgy + 1/2mv^2 ME = 56*9.81*y + 1/2*56*1^2 Ui + Ki = Ui + Ki gyi + 1/2vi^2 = gyf + 1/2 vf^2gyf = 1/2vf^2 vf = 5.425 m/s 9.81y + 1/2*1^2 = 9.81*1.5 + 1/2*5.425^2 y = 2.949 m MEi = 56*9.81*2.949 + 1/2*56*1^2 MEi = 1648 J The picture for this problem really confuses me. I am...
  34. dRic2

    I Phonon Number Conservation in a Single Mode Oscillation Experiment

    Suppose I prepare an experiment where I excite a single mode of oscillation of the lattice, that is something like ##u(x, t) = Ae^{i(kx-\omega t)} ## (in the classical limit). The energy corresponding to that mode should be ##E = \frac 1 2 \rho L^3 A^2 \omega^2 ##. If I equate this equation to...
  35. M

    Conservation of angular momentum and its counterpart for linear momentum

    Hi, I have just joined the forum. Thank you all for being a part of such places so that people like me can get answers to the questions on their minds! --------------------------- I have been trying to understand how a quadcopter yaws. Referring to the figure below which is bird's eye view of...
  36. Y

    Understanding energy conservation in a solenoid

    So let's assume ideal wire, resistance = 0 Ohms. Also assume there is a magnetic ball 1 meter away and is attracted to the solenoid. If you have a loop of wire and run a small current through it, you get a magnetic field. This field attracts the magnetic ball, over a distance of 1 meter. If...
  37. W

    I Conservation of energy in cosmology

    Models like Vilenkin's tunnelling from nothing model described here: https://www.sciencedirect.com/science/article/abs/pii/0370269382908668 claim the universe came from "nothing". It is claimed this doesn't violate any conservation laws because the negative energy of gravity and the positive...
  38. G

    A rocket and its gas exhaust velocity

    This isn't right, is it? -\dfrac{GM}{R}+\dfrac12 v^2=-\dfrac{GM}{R+h} v=\sqrt{\dfrac{GM}{R}}\left( 1-\sqrt{\dfrac{R}{R+h}}\right) He's doing energy conservation. The mechanical energy at the Earth's surface is equal to the energy when the speed is 0.
  39. A

    Hard Momentum Conservation Impact Problem

    I believe momentum conservation is to be used in this sum since there's no external force, but I am not sure how to write the equation. Can someone please help me out:)
  40. L

    Laws of conservation in special relativity

    Momentum ##\vec{p}## before collision is momentum of proton of the energy ##E=76.4\mbox{GeV}##. Law of conservation of energy is E+mc^2=E_1+E_2+...+E_n mc^2=0.94\mbox{GeV} We could generate only even number of particles after collision because of law of conservation of electric charge. Also...
  41. LCSphysicist

    Is there a proof about angular momentum conservation?

    Angular momentum can be exchanged between objects in a closed system, but total angular momentum before and after an exchange remains constant (is conserved). There is a proof about this conservation?
  42. D

    2-body problem - conservation of angular momentum

    Hi With the 2-body problem relating to planetary orbits i have encountered the following ; the gravitational force on the reduced mass acts towards the large mass(Sun) and since it is a central force it exerts no torque about the fixed centre(Sun) so angular momentum is conserved. Conservation...
  43. J

    Conservation of energy in transformers

    This question is given as an exercise in my book. I can't figure out whether this is a poorly worded question or if I misunderstand. The answer I can come up with is that power is dissipated over the load so more power is needed to be supplied by the ac source. This seems too hand-wavy to me...
  44. E

    ABS system on a two-wheeled vehicle - Conservation of Angular Momentun

    Hello, The question I have pertains to conservation of Angular momentum on a motorcycle. I know that the dynamic friction is less than the static friction, so when you are braking on a (say a motorcycle) and the wheels lock up, the bike is bound to fall over. This is the reason ABS (Anti-lock...
  45. L

    Law of Conservation of Energy Proof

    Although I am not too sure how to answer this quesion I have tried below. I realize that an electromotive force is a supply voltage, the energy transferred per unit charge when one type of energy is converted into electrical energy. However, EMF is not actually a force. It is usually measured...
  46. E

    Is conservation of energy derived from the work energy theorem?

    To my mind, there are two distinct approaches to energy problems that different authors tend to use, and I wondered whether either is more fundamental than the other. The first is variations on the work energy theorem, and the second consists of defining a system boundary and setting the change...
  47. L

    How does this capacitor circuit not violate conservation of charge?

    There must be something I'm not understanding about capacitors in series. I know that we can treat them as one equivalent capacitor with: (1) with 1/Ceq, (2) same Q as anyone of the capacitors, (3) and add up the Vs for the sum total V across them. If the equivalent capacitor (Ceq) would...
  48. D

    Conservation of linear and angular momentum

    Hi ; I have a few question regarding the conservation of linear and angular momentum. Would appreciate any help. 1 - When no external forces act are both linear and angular momentum conserved in all 3 directions separately or just the total linear/angular momentum conserved ? 2 - if I approach...
  49. kuruman

    Can We Do Better Than Mechanical Energy Conservation?

    Continue reading...
  50. George Keeling

    I Solving Geodesic Eq.: Mysterious Conservation Eq. (Sec. 5.4 Carroll)

    I'm still on section 5.4 of Carroll's book on Schwarzschild geodesics Carroll says "In addition, we always have another constant of the motion for geodesics: the geodesic equation (together with metric compatibility) implies that the quantity $$...
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