# 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. ### Circular motion of a Weightless rod

I used law of conservation of energy to calculate (d theta/ dt)^2 (from:mgasin theta=1/2m(d theta/dt.a)^2+1/2mu^2(u is the velocity of the C ring at time=t)), but wasnt able to find u(velocity of C).Is there any relationship between the tangential velocity of B(d theta/dt.a) and velocity of C(u)...
2. ### Proving Newton's 3rd law from conservation of momentum

I don't quite understand the "subtle point" at the end of the author's solution. Ok, let's imagine for a second that the external forces have an impact on the internal forces. How does that change the mathematical result that the two forces are equal and opposite to each other? Even if...
3. ### Classical Mechanics: Rocket Propulsion Calculation

My textbook says the correct answer for #79 is 1551 kg but I get 1600 kg. I just attempted to solve it using conservation of momentum. Can't see where the math is incorrect.
4. ### Oscillation of system of three charges

I tried to take angles and proceed by energy conservation But this doesn't seem to lead me anywhere . Here , the length of threads is ##l## each and ##2\theta## is the central angle. ##y_1## is the displacement of the charges attached at the extreme ends of the threads respectively while ##y##...
5. ### A Repeated measurements and granular space time

Hi Pfs, I would like to know if it would be possible for our known theories to derive conservation laws if space time was really granular. I think that entanglement is the only process which would succeed.
6. ### Using conservation of energy and momentum in projectile motion

I am going to use this coordinate system: According to the answer of the book, I think no force is acting on this projectile: Let's say at top of it's trajectory its velocity is ##u##. Conservation of energy : $$2E_0=\frac 1 2 m_1 v_1^2+\frac 1 2 m_2 v_2^2$$ Conservation of momentum in...
7. ### I Infinite flow with capillary tubes?

I was watching this YouTube video by the channel The Action Lab: At one point it shows this capillary tube phenomenon: It got me immediately thinking: Conservation of energy much? What's stopping that second tube from being bent into draining into the leftmost tube, thus creating an...
8. ### Lab Exercise: Measuring "g" using Conservation of Energy

Hi, so this is a lab in which we used an air track at an angle and a glider to gather some data through various trials, ultimately to calculate "g". L_glider = 10.15 cm x (photogate activation point) = 547.5 mm or 54.75 cm x_0 (release point) = 1800.0 mm or 180.00 cm (Δx)_midpoint = | x - x_0 |...
9. ### I Does entanglement always conserve something?

IIUC, entanglement sometimes plays a role in conserving come quantity like momentum or spin: the quantities measured for two particles must be correlated in order to get a certain total value. But is this always the case? For example, what, if anything, is conserved in the Hong-Ou-Mandel...
10. ### Conservation of energy problem: Ball rolling down inclined plane and then through a loop-the-loop

Hello, this question may seem weird but I really need help on this. To bring the formula for the height h of the triangle above, I have to create a relation between potential and kinetic energies of the black ball with mass m (I can't find any other methods than this). For a sphere falling...
11. ### I Seemingly a contradiction of conservation of energy?

I've had this question for a while now and I wonder if anyone can make sense of it. It's about two scenarios where the difference between them seems to contradict conservation of energy: Scenario 1: In a vacuum chamber, there is a robotic arm, a box, a lower platform and a higher platform. At...
12. ### Conservation of Energy with springs

Start by finding the equilibrium position, so we have {4mgx}/{a} = mg giving us x = a/4, therefore the spring's length is 5a/4. Now the loss in EPE (and therefore gain in energy of the particle) between the bottom and the equilibrium position is clearly 4mg((a/4 + d)^2 , and then from the...
13. ### B Ignoring the motion of the Earth for energy vs. momentum conservation

Hi. If I drop an inelastic body, its potential energy first gets converted to kinetic, then to deformation energy. We use conservation of energy without taking into account the kinetic energy gain of the earth during the fall. However, at first sight conservation of momentum seems to be...
14. ### What Causes the Loss of Mechanical Energy in a Frictionless Spinning Cylinder?

We all know we need to apply conservation of angular momentum here. This necessarily leads to a difference in mechanical energy. Since initial rotational inertial is less than final rotational inertia, there is a loss of mechanical energy. However, I have not been able to convince myself what's...
15. ### Troubleshooting Circular Motion: Solving the Toy Car Loop Puzzle

I tried using conservation of energy, and using the equations for circular motion, but I can't seem to find a solution. Any help?
16. ### B Conservation of Angular Momentum - Problem understanding this scenario

Hello, As far I know, in a closed system both, linear and angular monentums, are conserved. İmagine such a scenario: everything is motionless, both momentums zero initially, then from a disk are fired (compressed spring push) two equal mass balls at same speed but opposite direction. Now balls...
17. ### I Maxwell's equations and the momentum of charge

There appears to be a conservation of charge momentum (qv) analogous to that for mass (mv) although in the case of charge it is more potential in nature. A change in the flow of charge (or current) produces changing magnetic and electrics fields according to Maxwell's equations. These in...
18. ### 1999 AP Physics C Mech: Conservation of momentum and energy

Why is (1/2)(mv0)^2 = 1/2(M+m0)gh not a valid equation for conservation of energy? Isn't the energy from when the dart is shot the same as when the two masses move at speed v?
19. ### I Conservation of Momentum versus Conservation of Velocity

I have often wondered why Inertia , Newton's 1st Law, is not simply called Conservation of Velocity Can anyone give me a reason why it should NOT be called Conservation of Velocity ??? Conservation of Energy is valid in the absence of External Forces. Conservation of Momentum is valid in the...
20. ### Why does the given conserved quantity mean the motion is on a cone?

TL;DR Summary: . An electrone moves in a magnetic field ##B(\vec r)=g \frac {\vec r}{|\vec r|^3}##. Why does the conservation of the quantity $$\vec J=\vec r \times\vec p +eg\frac {\vec r}{|\vec r|}$$ mean that the motion is on the surface of a cone?
21. M

### Spring momentum conservation problem

For this problem, The reason why I am not sure whether it is a valid assumption whether momentum is conserved because during the collision if we consider the two masses to be the system, then there will be a uniform gravitational field acting on both masses, and a spring force that is acting...
22. ### Why Isn't Momentum Conserved with Varying Disk Radii?

Here is question + drawing.
23. ### I Why momentum is conserved when a gun fires? (conceptual question)

I understand that conservation of motion comes from the action and reaction pairs of newton's third law. When it is triggered, two forces appear that cancel when analyzed as a system. My question is how is it that momentum is conserved if before the shot there was no force in the system and...
24. ### I What do you need to establish that spin is conserved?

Hi. Question as in the summary. Spin has no obvious classical interpretation but it is often a conserved quantity and considered as some sort of angular momentum. What do you need to establish that spin is a conserved quantity? I'm finding references to situations where spin is not a...
25. ### Optimizing Vehicle Maintenance: Tips and Tricks from Mechanical Engineers

Hi guys, i’m always looking to conserve at best my motorcycle and car, i’m here to understand the correct way to do it
26. ### Conservation of Energy when lifting a box up off the floor

So, I cannot for the life of me write a conservation of energy statement, when an object is lifted up by a force. So in my example there is a box on the floor with v = 0, and then a force of magnitude F, where F > mg, acts on the ball, now the net force is F-mg, and hence the work done is (F -...
27. ### Solving Orbital Speed with Energy & Angular Momentum Conservation

I've already solved the orbital speed by equating the kinetic and potential energy in the circle orbit case. $$\frac{1}{2}mv^2 = \frac{1}{2}ka^2.$$And so $$v^2 = \frac{k}{m}a^2$$Now when the impulse is added, the particle will obviously change course. If we set our reference point in time just...
28. ### Do different length ramps violate conservation of energy?

mgh=(1/2)(m)(v^2) gh=(1/2)v^2 sqrt(2gh)=v Should have the same v, but this is not the case based on the answer and real-life experiments.

32. ### Conservation of relativistic energy, collision of particles

Question: With maximum do they mean that the speed of the pions is the same as the proton and an antiproton? Otherwise there will be two unknowns, and if I use both relativistic-energy and momentum conservation equations I get difficult equations.
33. M

### Helium balloon energy conservation

For this problem, How can energy be conserved if the bit highlighted in orange is true?Many thanks!

37. M

### Puck collision with rod using angular momentum conservation

For this problem, Why for part (a) the solution is, Is the bit circled in red zero because since the putty is released at a very small distance above the rod it velocity is negligible? Also for part (d) the solution is I did a computation of the initial and finial kinetic energies of the...
38. ### I Conservation of charge in the Universe

The charge of an isolated system is conserved. This implies the charge of the universe is constant. This implies that charge can neither be created nor destroyed. This implies that the net positive charge and the net negative charge of the universe are conserved. Is this right?
39. M

### Discovering Vector Direction in Conservation of Energy Problems

For this problem, Is the length vector into or out of the page and how do you tell? EDIT: Why must we use conservation of energy for this problem? I tried solving it like this: ##IdB\sin90 = ma ## ##IdB = ma ## ##v_f = (2aL)^{1/2} ## ##v_f = (\frac {2dIBL} {m})^{1/2} ## Which is incorrect...
40. ### Which system to apply conservation of momentum to?

For this problem I was very confused whether conservation of angular momentum should be applied to the person, the swing or the person-swing system. It seems to me that there is no net torque on any of the three systems I listed above. However, it seems that the angular momentums of the three...
41. ### The direction of flux vectors in derivation of conservation of mass

In the derivation of the conservation law of the conservation of mass, the flux on one side enters and the flux on the other side leaves the control volume. I presume this is due to the assumption that the volume is infinitesimally small and hence v(x,y,z,t) will not change directions...
42. ### I Conservation of Energy in GR: A-B System Analysis

Assume you have a two particle system, A, which has a mass and gravitational pull of g, and B, an object with low mass, The system starts at time 0 with the distance between A and B being 0, A being at rest and B having enough kinetic energy to move it a distance r away from A, until time t all...
43. ### Surely this will NOT work: violation of conservation of momentum?

The rotating ball should push the vehicle first to the right and once it hits the airbag - to the left?? Even if this works, how are you going to automate it and repeat it?
44. ### I Are SM B & L conservation violations through sphalerons possible?

It isn't often that you see this many bold claims in a five page Letter, the abstract and citations of which appears below. The conclusion I find most interesting is this Letter's conclusion that contrary to the current consensus understanding of the mathematics of the Standard Model (mostly...
45. ### I Charge conservation and special relativity

If conservation of charge gets violated in future experiments, what would be the implications on relativity? I have some faint idea that this will cause photons to have non-zero rest mass, but does this affect special relativity at all? Also, does special relativity make conservation of charge...

48. M

### I Can we solve this Morin's problem without conservation of string?

For this problem, The solutions are, However, how would we solve this without using the idea of conservation of string? Can we apply Newtons second law to each mass? My working is: Then apply Newton's Second Law to each pulley, (Line 1) (Line 2) (Line 3) (Line 4) Many thanks!
49. ### System of particles, impulse and conservation of angular momentum

So i was able to solve the angular velocity part but i don't know how to find the velocity of centre of mass . For the first part i simply conserved momentum about COM because if i consider the particles as a part of the same system as rod the collision are internal forces . I am mainly...
50. ### I Conservation of energy in quasar outflows?

I found this article* about the behavior of quasar outflows in cosmology and how they can create a magnetic field. In section 2.1.4., the authors say that when a quasar produces a "wave" or an outflow, the material will be emitted with energy coming from both the quasar itself and the Hubble...