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. P

    I Understanding Hamiltonian Conservation Laws

    I'm a little confused about the hamiltonian. Once you have the hamiltonian how can you find conserved quantities. I understand that if it has no explicit dependence on time then the hamiltonian itself is conserved, but how would you get specific conservation laws from this? Many thanks
  2. J

    Conservation of energy at terminal velocity

    Homework Statement A spherical object is dropped from an elevation great enough such that it will achieve terminal velocity for some period of time before hitting the ground. Once terminal velocity is achieved what is gravitational potential energy converted to. Homework Equations Ug = mgh Ke...
  3. J

    Collision Conservation of Energy

    Homework Statement An 8.00-g bullet is fired horizontally into a 9.00 kg block of wood on an air table and is embedded in it. After the collision, the block and the bulet slide along a frictionless surface together with a speed of 10cm/s. What is the initial speed of the bullet? M1 = 0.008kg...
  4. G

    Conservation of momentum in gyroscopes

    Not a scientist, please be nice :) Let's assume I have a singe axis gyro (flywheel) spinning in space. I apply a force to a point which results in a change in pitch. I apply this force until the gyro is at 5* pitch and then stop. Will the gyro continue to change pitch after the force stops...
  5. RoboNerd

    Conceptual question on angular momentum and Emech.

    Homework Statement A 60.0 kg woman stands at the western rim of a horizontal turntable having a moment of inertia of 500 and radius 0f 2.00 m. Turntable is initially at rest and is free to rotate around frictionless vertical axle through its center. Woman then starts walking around the rim at...
  6. D

    Using conservation of angular momentum as a braking system

    Hello, I have a question about using the properties of conservation of angular momentum to provide mechanical resistance. Basically, I'd like to create a device that spins a disk similar to a gyroscope. The device has an external input that, depending on the configured orientation of the disk...
  7. A

    Conservation of energy in a rocket

    Imagine I have a rocket with a certain amount of energy stored as chemical energy, let's say its 10Js, that exhausts itself after 5 seconds. If I attach this rocket to a (relative to an observers frame) stationary cart in such a way that it pushes the cart, it will add 10J of kinetic energy to...
  8. A

    Rotational Kinetic Energy and Conservation of Momentum

    I am having trouble wrapping my head around a physics concept. If we roll solid sphere down an inclined plane it will reach the bottom at a different time than if we were to say, roll a hoop down the same inclined plane. This is because they have different rotational inertias, and so more of...
  9. C

    Does Conservation of Momentum Apply to Electron/Atom Interactions?

    Electrons have a theoretical rest mass. They can move at varying speeds through space, unlike photons. They ehxhibit quantum-characteristics in their behavior. If an electron collides with, say, an atom, does conservation of momentum apply in the classical sense or does measurable mass (an atom...
  10. emeriska

    LRC equation using Poynting theorem and conservation laws

    Homework Statement We have an ordinary LRC circuit with inductance L, capacitance C and resistance R with an oscillating voltage with low frequency (U^e). Using the energy conservation law and Poynting's theorem, find the differential equation: $$L \frac{\partial ^2}{\partial t^2}I + R...
  11. C

    [Traffic Flow] Concrete example of conservation equation?

    This is it; most likely the last time I bother the people of this website with my questions on traffic flow. I'm trying to figure out some concrete examples to demonstrate utilization of the conservation equation in traffic flow: \frac{\partial \rho }{\partial t} + \frac{\partial q(\rho...
  12. weirdlycool

    Conservation of momentum (relative speed)

    Homework Statement Consider a gun of mass M (when unloaded) that fires a shell of mass m with muzzle speed v. (That is, the shell's speed relative to the gun is v.) Assuming that the gun is completely free to recoil (no external forces on gun or shell), use conservation of momentum to show that...
  13. D

    Conservation of energy interpretation of percentage conserved

    Homework Statement I get that less percentage energy is conserved from potential to kinetic energy by measuring h and v with two balls for the heavier ball. I am trying to sort of why actually is like that! Two balls where dropped down from a ramp with different masses and volume. The smaller...
  14. Kernul

    Law of Conservation of Mechanical Energy Exercise

    Homework Statement A mass ##m_1 = 5.0 kg## is hanging from the end of a thread, of negligible mass, that slides on a pulley, of negligible mass too and without friction. At the other end of the thread, at the same height of ##m_1##, there is another hanging mass ##m_2 = 3.5 kg##. Using the Law...
  15. Sirsh

    Conservation of angular momentum & linear momentum

    Two things I'd like to discuss: 1. The conservation of angular momentum. If you have two discs rotating on the same fixed rigid axis, will these nullify each other? I.e. Create no net angular momentum? 2. How / is it possible to convert angular momentum to linear momentum in the sense to be...
  16. W

    Exploring Rocket Momentum Conservation: A Followers Tale

    I would like to preface this by saying that I do not in any way resemble a physicist - and I'm sure the crudeness of my work will confirm that, but I thought that this was so cool, I wanted to share it. I'm just a follower of physics. I understand that some of the concepts I'm going to be...
  17. K

    Conservation of Angular Momentum; angle of rotation

    Homework Statement A block of mass m slides down a frictionless ramp from height h above the floor. At the base of the ramp it collides and sticks to the lower end of a uniform rod, length L, mass 2m, that is suspended about a pivot at point O, about which it is free to rotate. Express...
  18. A

    How Do You Prove the Law of Conservation of Momentum in Collisions?

    Homework Statement This lab I have the mass and change in distance measurements for inelastic collisions; and then we did an elastic collision one where we determined the mass and measured the times three of them simultaneously where we measured it as it bumped the car. So I am supposed to...
  19. D

    2D Elastic Collision Using Conservation of Momentum

    Homework Statement Two objects collide and bounce off one another. After the collision, object m1 = 2.74 kg moves off at 12.8 m/s at a heading of 295 degrees. Object m2 = 2.28 kg moves off at 12.8 m/s at a heading of 241 degrees. Initially, m2 was traveling at 11.1 m/s at a heading of 334...
  20. B

    Question about angular momentum conservation

    Homework Statement Question - Models of global warming predict that large sections of the polar ice caps will melt. Explain what effect this will have on the rotation of the Earth, however slight. Homework Equations L = Iw The Attempt at a Solution Assuming polar ice caps protrude the earth...
  21. Cathr

    How Does Energy Conservation Apply in a Pendulum-Object Collision?

    1. A ball hanging on a pendulum hits an object standing on the table. The interaction is elastic and linear. After that, the object falls on the floor. Homework Equations From state 1 to 2, we have the conservation of the potential energy of the pendulum to its kinetic energy, right before...
  22. G

    Solutions for a quadratic system of equations

    Hi, I'm looking for the real solutions to the system \begin{array}{rcl} 1 & = & v_1+v_2+v_3+v_4+v_5 \\ 1 & = & v_1^2+v_2^2+v_3^2+v_4^2+v_5^2 \end{array} Background: I'm looking at a Newton's cradle with 5 balls, each of mass ##m=1##. The first ball is pulled away and let go such that it hits...
  23. K

    Conservation of momentum and nuclear decay (Gr 12 Physics)

    Homework Statement A stationary nucleus undergoes radioactive decay. A beta particle and a neutrino are detected leaving the nucleus. What is the recoil velocity of the remaining nucleus? If the recoil velocity measured is significantly different from the calculated velocity, what conclusion...
  24. G

    Pendulum: Energy is conserved but not momentum

    Hi. In an ideal pendulum, energy is conserved. Potential energy gets transformed to kinetic energy and vice versa. However, momentum is not conserved. The latter means that the pendulum is not an isolated system, which is plausible, since gravity is an external force. But why is energy...
  25. AntoineCompagnie

    Why is the work of a constant force conservative?

    Homework Statement Why for a given constant force, in a study reference system, which point of application moves from A to B, the work of the force is conservative? Homework EquationsThe Attempt at a Solution The only thing I know is that if the angle ##(\vec{F},\vec{AB})## is acute...
  26. H

    How does the law of conservation apply under these condition

    A person of 60 kg is holding on a rope of 3m while standing on a the ledge of a building of height 7m. The rope is fixed to a point at roughly eye level 3 m from ledge. The person walks off the building and is swung in a vertical circle. If the person let's go at approximately the same height he...
  27. M

    Why Use Time Derivative Outside the Integral in the Continuity Equation?

    Hi PF! Can someone help me understand why, when writing the continuity equation we write: $$\frac{\partial}{\partial t} \iiint_v \rho \, dv$$ instead of $$ \iiint_v \frac{\partial}{\partial t} \rho \, dv$$ I understand the two are not necessarily the same, but why derive it the first way...
  28. gracy

    Conservation of angular momentum

    If there is no net torque acting on a system total angular momentum of the system will be conserved as well as angular momentum of each body present in the system will be conserved. And if there are two bodies /two charges present as a system and one of them (let's say body 1 )produces torque...
  29. T

    Conservation of momentum in an *open* system

    i got in an argument with my physics teacher about a test question recently, and am still reluctant to abandon my logic. The question is a standard explosion problem, akin to this: A firework is placed in the midst of some motionless billiard balls. The firework goes off and the billiard balls...
  30. S

    Conservation of Energy Question

    Having problems with part (c) here, question is attached below in full. Homework Statement Using the equation 1/2 * Load * Displacement = Sum of (P^2 * L/2AE) From the past questions I have the following info, these are also included in the solutions so are accurate: A = 1x10^3 m^2 FAB =...
  31. RoboNerd

    Understanding why the initial height of one block is equal t

    Homework Statement A 20.0-kg block is connected to a 30.0-kg block by a string that passes over a light frictionless pulley. The 30.0-kg block is connected to a spring that has negligible mass and a force constant of 250 N/m. The spring is unstretched when the system is as shown in the figure...
  32. A

    Collision of rolling billiard balls

    Homework Statement There are two problems: (A) Consider two identical billiard balls (spheres), each of mass M and radius R. One is stationary (ball 2) and the other rolls on a horizontal surface without slipping, with a horizontal speed v (ball 1). Assume that all the frictional forces are...
  33. P

    Rotational Motion: Momentum Conservation

    Homework Statement A solid sphere is set into motion on a rough horizontal surface with a linear speed v in the forward direction and angular speed v/r in the anticlockwise direction. Find the linear speed of the sphere when: a) When it stops rotating b) when slipping ceases Homework...
  34. P

    Conservation of Energy and General Relativity

    I was reading through some main stream scientific literature, and I came across Sean Caroll's "Energy Is Not Conserved" post. Essentially, he contends that through general relativity energy is not conserved, at least not in conventional manner of thinking about energy. Anyways, some portions of...
  35. L

    Conservation of energy and space expansion

    This had me thinking for a while. Imagine a photon emitted by a very distant object at a redshift of z = 2.0 for example. As the photon travels through space, due to space expansion the photon's wavelength will shift towards red. With an increase in the wavelength there must come a decrease in...
  36. H

    Definitions of parity conservation

    Definition 1: The expectation value of the observable related to the parity operator ##\hat{P}## is constant over time. That is, \frac{d}{dt}\langle P\rangle=0 \int\Psi^*(r)\ \hat{P}\ \Psi(r)\ dr=constant \begin{align}\int\Psi^*(r)\ \Psi(-r)\ dr=constant\end{align} Definition 2: If the...
  37. E

    Symmetry and conservation.... which is first?

    I have a question. According to Noether's theorem, "For each symmetry of the Lagrangian, there is a conserved quantity." But soon I thought that I can also prove "For each conserved quantiry, there is a symmetry of the Lagrangian." Actually I can prove the second statement if I start prove...
  38. S

    I Don't agree with law of conservation of energy

    Well this question has been in the mind since a long time. I believe that the law of conservation of energy is not true. If it is/was true then why would the universe expand and into what is it expanding ? obviously energy is created when the universe expands into "NOTHING". I will be waiting...
  39. M

    Conservation law for any potential field?

    Consider a free particle moving in a general time-dependent scalar potential. Energy & momentum are not conserved. However, there is a symmetry in the lagrangian: the velocity appears only as its square, so we can rotate it without affecting the value of L. What conservation law results from...
  40. REVIANNA

    Energy and momentum conservation

    Homework Statement [/B] A block of mass m is attached to a spring with a force constant k, as in the above diagram. Initially, the spring is compressed a distancex from the equilibrium and the block is held at rest. Another block, of mass 2m, is placed a distance x/2 from the equilibrium as...
  41. J

    Conservation of Angular Momentum for a Satellite

    Homework Statement https://scontent-sea1-1.xx.fbcdn.net/hphotos-xft1/v/t35.0-12/12414351_10206719685063143_386848762_o.jpg?oh=16c004481b7417fad921c37acc4942be&oe=56793416 Homework Equations Angular momentum: H= Iw Parallel axis theorem: Io = I + Md^2 Moment of Inertia of thin plate about it's...
  42. T

    Is Conservation of Energy the Key to Solving This Tricky Problem?

    I find this problem kind of tricky. I think it must be a, since a change in momentum of the car causes the same change in momentum of the earth.
  43. DoobleD

    Conservation of energy and momentum transfer

    Let's say a tennis ball with velocity with only an horizontal component hits a vertical wall at rest. After collision, conservation of momentum tells that : m_{wall}v_{wall} = 2m_{ball}v_{ball} Thus, the wall has now a (tiny) velocity and kinetic energy : v_{wall} =...
  44. L

    Two slit diffraction and energy conservation

    Hi all, I have a small misunderstanding about the energy conservation in diffraction from 2 slits. First, I understand the energy conservation of interference from 2 slits. If intensity from each slit is I, then I have intensity of 2I after slits plane. Interference is given by: So at bright...
  45. D

    Conservation of momentum question

    Homework Statement Homework Equations m1v1+m2v2=m1v1+m1v1 after The Attempt at a Solution my answer = -1m1v1 because the wall is not moving so its velocity is 0 therefore m1v1 = m1-v1 after I put -v because it is the same just bounces in the opposite X direction I found somewhere...
  46. J

    Question on conservation of angular momentum

    Dear guys, Recently, i am confused with a problem in my textbook of mechanics. The question is, suppose there is a disk, placed horizontally, rotate about its center with angular velocity ω. A ball move with respect to the center of the disk in a trace of Archimedean spiral r=αθ. The angular...
  47. R

    Conservation of momentum and lost energy

    Homework Statement sorry for the long question. Homework EquationsThe Attempt at a Solution I get everything up until it asks where the extra "half" of the power is spent. I do know that the extra half is referring to the "2" dK/dt. I have spent the last hour or so thinking about this...
  48. J

    Conservation of angular momentum book problem

    Homework Statement 2. The attempt at a solution I set the initial angular momentum of the disk = to the sum of : rod's angular momentum, angular momentum of disk, rod's center of gravity and disk's center of gravity. With the reference point being at B. Why is the velocity of the rod's...
  49. S

    Conservation of Energy in a Pulley System

    Homework Statement Two masses are connected by a light string passing over a light, frictionless pulley, as shown in the figure below. The mass m1 (which is greater than m2) is released from rest. Use the isolated system model to answer the following. In terms of m1, m2, and h, determine the...
  50. K

    Conservation of Angular Momentum

    Homework Statement Indiana Jones standoff. Person A fires a 20g bullet at 500 m/s at Person B, who is holding a sword. The bullet sticks to the sword. The angular momentum of the sword is 2.225 kgm^2 / s. The moment of inertia about the center of mass of the sword is .7082 kgm^2. The...
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