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. ermia

    Solving LC circuit with energy conservation

    krotovs solution is based on energy conservation. My question is that why the solution didn't consider inductors energy? the question: The solution:
  2. H

    Energy conservation: electromagnetic wave in matter

    Hi, I completely failed this homework. I mean I think I know what happen, but I don't know how to show it mathematically. The energy lost by the wave is used to oscillate the electrons inside the conductor. Thus, the electrons acts like some damped driven oscillators. I guess I have to find...
  3. K

    Conservation of probability issue when solving ODE in Mathematica

    I am trying to solve this two level (Schrodinger) equation as a function of time:$$i\begin{pmatrix} \dot{x}\\ \dot{y} \end{pmatrix} = \begin{pmatrix} 0 & iW+dE_0sin(\omega t)\\ -iW+dE_0sin(\omega t) & \Delta \end{pmatrix}\begin{pmatrix} x\\ y \end{pmatrix}$$ (I can go into more details about...
  4. SMOKEYWC

    Conservation of momentum (wrecking ball hits a stationary object)

    I have a wrecking ball with a mass of .5kg traveling at 3.03 m/s that hits a stationary block .9 meters high, weighing .06kg. I calculated the ball's exit velocity after it hits the block to be -3.00 m/s . I calculated the final velocity of th block to be 4.2 m/s Vf = Sqrt 2(g)(h) = sqrt...
  5. Demystifier

    A Can local conservation be verified experimentally?

    This question was raised but not answered in a thread which is now permanently closed. Consider the local conservation of charge ##\partial_{\mu}j^{\mu}=0##. In quantum field theory it is valid as an operator identity, but operators as such do not have a direct operational (experimental)...
  6. C

    Why doesn't this solution work? (Springs and Conservation of Energy)

    I already know the solution to this, all you do is set the height of the top of the trampoline to 0 and solve for initial velocity so the equation for the conservation of energy $$mgh_0 + \frac{1}{2}mv_0^2 + \frac{1}{2}kx_0^2 = mgh_1 + \frac{1}{2}mv_1^2 + \frac{1}{2}kx_1^2$$ becomes...
  7. S

    Apparent weight problem (kinematics + conservation of Energy + Newton's laws)

    Hello there, I have tried the problem but don't get a different of 6g's as I am supposed to. I am not sure whether I interpreted the problem in the correct way, but I would love some feedback/hints on what went wrong in my solution, thanks in advance. Solution: SITUATION DRAWINGS + FBDS so...
  8. mr_sparxx

    I Kepler's second law derivation from angular momentum conservation

    Many texts state that in an elliptic orbit you can find angular momentum magnitude as $$ L = r m v = m r^2 \frac {d \theta} {dt} $$ I wonder if $$ v = r \frac {d \theta} {dt} $$ is valid at every point. I understand this approximation in a circumference or radius r but what about an arc...
  9. S

    Conservation of energy problem with friction included

    so I haven't looked at the solution yet, but I know that a 100% the velocity needs to be bigger, but analytically, I get a - sign instead of a + sign as you'll see at the final square root. So for the first 15meters of the motion all you should know is that ##v_1 = 10.458 m/s##. for the 2nd...
  10. S

    Car-Car System: Energy Conservation?

    this is an easy problem but would it be possible to consider car-car system. What I did on paper was carsystem and because they have the same properties(mass en speed) multiply by ##2## solution for car-car-earth system I assume is the following if it is possible? solution for car-car: law or...
  11. M

    B Conservation of Momentum for system of particles

    We know that if we take two particles and assume no external force is applied then by Newtons third law total momentum gets conserved after collision. If we take three particles and there is collision between them and no external force then the momentum is again conserved for each pair like in...
  12. A

    B Conservation of momentum and conservation of energy details

    If we have a ball with mass m dropped from a height h down to the ground, how come we can't set the conservation of energy equation just as the velocity of the ball turns 0. mgh = 0 If instead the ball were moving with an initial velocity v, would the equation be ##mgh + \frac{1}{2}mv^2 = 0##...
  13. AspiringPhysicist12

    Conservation of momentum problem (sand-spraying locomotive)

    If I consider only the freight car's mass and the mass dm that's added to the freight car as part of the system, then I get this answer: https://ibb.co/QfKSqQ5 But if I consider the freight car's mass, the mass dm, and the locomotive car as part of the system (maintaining the locomotive has...
  14. GopherTv

    B What are the energy conservation principles at play in a catapult launch?

    This is the catapult. At equalibrium the spring is 0.09 meters in length. When its fully stretched out its 0.225 meters long and I place a rock (0.205 kg) close to where my finger is on the catapult. The catapult starts with this much energy because 1/2 * k * x^2 90.54 is the spring constant...
  15. M

    Conservation of Energy in Trampoline Bounce

    I was able to calculate the correct answer (given by a solution sheet), V=5.364 m/s, using the momentum impulse equation, P0+J=Pf. If this value is correct, however, I don't understand how energy is being conserved. The speed increases after the person bounces off the trampoline while the mass...
  16. A

    I Conservation of angular momentum during collisions

    Hello everyone, I have a doubt regarding the conservation of angular momentum. When dealing with collisions between two objects, if the net external force is zero we know that the linear momentum is conserved; even when the system is not isolated, for instance because of gravity acting on the...
  17. Lars Krogh-Stea

    B Energy Conservation w/ Charged Battery Time Travel

    Hi! I want to start with saying that I'm not an expert on these type of problems, but I will be gratefull for some calarifications. I've heard that there's nothing in psysics that says that time travel is impossible. I want to make a case with the time traveling battery. Could be any mass with...
  18. qsduahuw

    Angular momentum / conservation of momentum questions

    I thought the answer is B because the angular momentum in conserved in all 3 pictures. <Moderator's note: Use of external servers not allowed. Please upload all images to PF.>
  19. A

    I Conservation of angular momentum -- spinning a bicycle wheel in space

    Suppose we have a rotating body like a bicycle wheel in space away from gravity. This body stops after a while due to friction between the wheel and wheel axles. Is not the conservation of angular momentum violated?
  20. J

    B Conservation of Energy and Momentum in an Explosion

    Hey, I have a question about explosions and how kinetic energy works during them. I have outlined my question on the attached image. Please let me know if something is wrong or needs clarifying. Thank you.
  21. T

    Conservation of energy -- Using a spring to launch a ball up an incline

    Ei = 1/2 K (x)^ 2 K = .0152N/m x = .0375 m Ei = 1.06x10^-5 Ef= 1/2mv2 + mgh m = .164kg, v is unknown, h is .0375sin(8.3)=.00541, Ef set equal to Ei 1.06x10^-5=1/2(.164kg)(v^2)+ (.164kg)(9.8)(.00541) v = .3254m/s I have gotten this answer multiple times but it is not correct. I am going...
  22. Shreya

    Momentum Conservation: Bullet enters a block

    I can understand that using conservation of momentum, we can find v. But we need V for that. The equation for V involves h and so we need h. But I am not able to comprehend the equation involving l,h and a. The question doesn't specify what a is. Please be kind to help
  23. Samama Fahim

    I Time Dependent Sinusoidal Perturbation Energy Conservation

    The transition probability -- the probability that a particle which started out in the state ##\psi_a## will be found, at time ##t##, in the state ##\psi_b## -- is $$P_{a \to b} = \frac{|V_{ab}|}{\hbar^2} \frac{sin^2[(\omega_0 - \omega)t/2]}{(\omega_0 - \omega^2}.$$ (Griffiths, Introduction...
  24. F

    B Quantum entanglement and energy conservation

    As my current studies have proven conservation of energy is a universal law. How is it possible for two entangled particles to be equally or similarly affected when a force or energy is applied to a single member of the entangled pair? The production of such a pair would be invaluable to...
  25. S

    Conservation of momentum of spacecraft and asteroid

    By "DART will have a relative speed of 6250 ms-1 when it collides with the asteroid", I assume it is the relative speed of the DART with respect to the asteroid. Using that assumption, I can answer question (a) For question (b), I don't understand the solution from the teacher. He did it like...
  26. Amaterasu21

    I Energy conservation in Doppler (NOT cosmological) redshifts?

    Hi all, My question is about Doppler redshifts, but I'm going to mention cosmological redshifts first because I'm a lay person as far as cosmology's concerned (I'm an amateur astronomer and did a few introductory astrophysics/cosmology courses at university, but my degree focus was planetary...
  27. Ineedhelpwithphysics

    Conservation of Momentum problem — Firing a cannonball

    So I am guessing the cannons final velocity will be 4 m/s to the left because there momentum before shot was 0 because of opposite and equal reaction so 50,000kg x -4 m/s + 20kg x 10,000 m/s = 0 ?
  28. S

    Kepler's Third Law vs Conservation of angular momentum

    The classic way to go about this problem would be to use Kepler's laws and thus find the new time period of earth. However I encountered this question in a test on rotational motion which deals with conservation of angular momentum. The equation used here would be I1ω1= I2ω2 Replacing I with MR2...
  29. RogerWaters

    B Why doesn't cosmic inflation violate conservation of energy?

    Hi all, I'm not a physics student (although I have a PhD in a different field) and so don't have the math, but I'm trying to interpret a key passage from Krauss' book 'A Universe from Nothing' where he is (trying?) to explain, in 'layman's terms', what Alan Guth termed 'the ultimate free lunch'...
  30. S

    Problem of spring block system: force vs conservation of energy

    I have used the work energy theorem like all source have shown me an have arrived at the right answer where work one by all the forces is the change in kinetic energy -1/2kx^2 - umgcosΘx +mgsinΘx = 0 is the equation which becomes -1/2kx -umgcosΘ+ mgsinΘ = 0 where k= spring constant u=...
  31. E

    I Momentum conservation for EM-Field/matter interaction

    Hello, I'm reading Feynman Lectures Vol II, and saw this "paradox" in section 26-2 (Figure 26-6), where two orthogonally moving charges can be shown to have unequal action and reactions. Later in Chapter 27, the explanation was given briefly citing field momentum. I tried to prove this...
  32. greg_rack

    Engineering Solving Momentum Conservation Problems: Tips & Tricks

    Hello guys, could someone give me a small hint to get me started on attempting this problem? I really cannot figure out how to relate conservation of momentum to the fact that there shouldn't be friction... does it have something to do with the so-called "sweet spot" of the ball? But then...
  33. A

    I Conservation of KE, wedge striking ball

    So assume we have a wedge traveling at a constant V horizontally, that is braced so it CANNOT move vertically. Ignore air and friction. See picture. It hits a stationary tennis ball and due to the angle, there is a net force on the ball as shown. The energy should come from the kinetic...
  34. greg_rack

    Conservation of linear momentum, undergrad particle dynamics

    Hi all, I'm opening this thread because of my uncertainty in how to correctly approach this exercise. My first thought was that, since the plate is subject to friction with the floor, it is going to stop, thus the final moment is 0. Hence, from the conservation of linear moment: $$m_Av_A+\sum...
  35. B

    B Conservation of momentum in a closed system

    In a closed system consisting of a set of particles not at rest relative to each other and acting on each other only by classical mechanical collision (i.e. billiard balls model, not including gravity or other long-range interactions), does conservation of momentum imply that the system will...
  36. J

    I Interference and conservation of energy in a resonator

    It is known that constructive interference in one place must be compensated for by destructive interference in another. Take a simple Fabry Perot resonator for example. The interference occurring at both sides of the first mirror (assuming one incident electric field) compensate each other out...
  37. C

    B Colliding balls: Conservation of momentum and changes in kinetic energy?

    I got curious about firearm ballistics and googled something similar to "bullet momentum vs kinetic energy". IIRC, momentum P = mv (checked); and kE = (mv^2)/2 (also checked). So I essentially wondered if it's worse to get hit by a bullet with greater kE than by one with lesser kE, presuming...
  38. tiago000000

    Exploring the Law of Conservation of Energy with a 5kg Weight and 10L Bucket

    Hi everyone! I regularly use the forum to learn but never registered to post anything, as I have nothing to teach really… But today I have a question regarding the law of conservation of energy that I can’t find the answer to, and maybe someone will help me understand: (I’ve attached a drawing)...
  39. J

    I Fresnel equations and conservation of energy (phase shifts)

    Quantum mechanically speaking when we split a wave in two the resulting waves must have a 90 degrees phase difference for energy to be conserved. Take the beamsplitter depicted in [1] for example. But the Fresnel equations state that the reflected wave should experience a phase shift of π when...
  40. Andrew1235

    Mass conservation in a sphere to find radial velocity of a flame

    I am not sure what form of mass conservation to use to solve the above problem from An Introduction to Combustion by Stephen Turns. Can anyone explain what form of mass conservation applies to a sphere in this context?
  41. casualguitar

    Modelling of two phase flow in packed bed using conservation equations

    Previously, I have seen the derivation of the energy conservation equations for simulation of single phase flow in a porous media (a packed bed). These are the energy equations for the solid and fluid respectively: I understand the derivation, however, these equations will only work when the...
  42. K

    Find the Conserved Quantity of a Lagrangian Using Noether's Theorem

    So Noether's Theorem states that for any invarience that there is an associated conserved quantity being: $$ \frac {\partial L}{\partial \dot{Q}} \frac {\partial Q}{\partial s}$$ Let $$ X \to sx $$ $$\frac {\partial Q}{\partial s} = \frac {\partial X}{\partial s} = \frac {\partial...
  43. Nick tringali

    How Does Energy Conservation Apply to MCAT Physics Problems?

  44. stephenklein

    Conservation of the Laplace-Runge-Lenz vector in a Central Field

    I actually have worked through the solution just fine by taking the derivative of \vec{L}: \frac{d \vec{L}}{dt} = \dot{\vec{v}} \times \vec{M} - \alpha \left(\frac{\vec{v}}{r} - \frac{\left(\vec{v} \cdot \vec{r}\right)\vec{r}}{r^{3}}\right) I permuted the double cross product: \dot{\vec{v}}...
  45. amjad-sh

    I Single-slit diffraction experiment and the conservation of energy

    In a single-slit diffraction experiment, a monochromatic light of wavelength ##\lambda## is passed through one slit of finite width ##D## and a diffraction pattern is observed on screen. For a screen located very far away from the slit, the intensity of light ##I## observed on the screen in...
  46. R

    B Why exactly do Virtual Particles not violate Conservation of energy?

    Recently I've read more about virtual particles and at first I tought that there were only doubts that virtual particles are not interpretable with the help of uncertainty principle. Furthermore it can't be used an an "excuse" for the temporary violation of the conservation of energy. Can...
  47. Andrew1235

    Conservation of energy for a series of elastic collisions

    The speed of the block after the nth collision is $$ V_n=(2e)^n*v_0 $$ By conservation of energy the block travels a distance $$V_n^2/(2ug)$$ on the nth bounce. So the total distance is $$ d=1/(2ug)∗(v_0^2+(2ev_0)^2...) $$ $$ d=1/(2ug)∗(v_0^2/(1−4e^2)) $$ $$ d=1/(2ug)∗(v_0^2∗M^2/(M^2−4m^2))...
  48. elcaro

    I Energy conservation in an expanding universe

    The total amount of energy is still a conserved quantity, even in an expanding universe based on a positive and constant energy density, and even under the rapid exponential expansion during inflation, total amount of energy is conserved. For how this works, see this lecture by Alan Guth, the...
  49. U

    Some help in understanding energy conservation

    While I am working through proving the homework statement, I encountered a problem. The problem is as follows: From the energy equation above, one can see that the minimum value of ##p## is ##m_T##. However, how does one explain why when ##p=m_T##, ##\sqrt{m^2_B+m^2_T}>m_A##?
  50. G

    I Conservation of momentum in a collision

    Now, deriving relativistic momentum isn't terribly difficult, but that's not the same as understanding it. I'm trying to figure out why conservation of momentum in special relativity requires the gamma factor. When I looked at conservation of momentum in elementary physics, we basically just...
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