Conservation Definition and 999 Threads

Homework Statement Newton's cradle. Each ball is 50 g. First ball is raised to 3.0 cm, and the final ball reaches 2.6 cm after the collision. 1) Use the law of conservation of energy to calculate its velocity before impact. 2) Use the law of conservation of momentum to determine the velocity of...

Homework Statement An 82-kg lumberjack stands at one end of a 380-kg floating log, as shown in the figure (Figure 1) . Both the log and the lumberjack are at rest initially. If the lumberjack now trots toward the other end of the log with a speed of 2.7 m/s relative to the log, what is the...

Homework Statement A plate drops onto a smooth floor and shatters into three pieces of equal mass. Two of the pieces go off with equal speeds v at right angles to one another. 1. Find the speed of the third piece. 2. Find the direction of the third piece. Assume the motion of the two pieces...

Imagine a ball rolling down a hill or inclined plane without slipping from a particular height. The conservation of energy law says that the final energy remains the same as the initial energy. But, when a ball is rolling without slipping, there must be a friction. So, what I think is E = E' mgh...

I know that momentum is conserved if there are no external forces. But, can you tell me what external forces are ? The site http://www.physicsclassroom.com/class/energy/Lesson-2/Internal-vs-External-Forces says that internal forces are force of gravity and force of spring. But, I think that...

Let ##L(\vec{r},\dot{\vec{r}})## be the lagrangian function, usually to get angular momentum conservation one impose ##\delta L=0## and form there we get ##\sum \vec{r}\wedge m\vec{v}=const##. There is however a conceptual problem with this procedure related to the fact that invariance under...

Homework Statement Suppose, a rod of negligible mass has two balls(A & B) at its two ends. Both the balls have same mass m. The rod is rotating around its center C with a uniform angular velocity ##\omega##. Another ball D (mass M) has a velocity v. At some time, A and D collide with each...

I always see that a ball moving in a constant speed collide with another ball is common conservation of momentum problems. Obviously, I know that the momentum is mass*velocity But, what if the ball accelerates and collides with another ball ? I think I can't use mass*velocity for the momentum...

Homework Statement A spring of negligible mass has force constant k = 1800N/m . You place the spring vertically with one end on the floor. You then drop a book of mass 1.20kg onto it from a height of 0.500m above the top of the spring. Find the maximum distance the spring will be compressed...

Imagine bringing a toaster and a slice of bread into space. After doing so, we were to toast the slice, measure the temperature after toasted, then chuck the piece of toast out into space quickly before too much heat transfers. After a week goes by, we find the piece of toast and bring it back...

Homework Statement http://www.sumoware.com/images/temp/xzmomoeqpspoqxcq.png A block with mass m is static at first at the height of 2R (see picture above) and then slides without friction. a) Determine where the block leaves the track b) Determine the maximum height which the block reaches...

Are fluctuations of the electron/positron field correlated in space and time because of charge conservation? We can't just have some positive charge just pop into existence, even if only for a moment? Thanks for any help!

Problem statement, equations, and work done: A particle called a Kaon is moving at 0.8c through a detector when it decays into two pions. Kaon particle: mass = 493.7 MeV/c^2 Pion+: mass = 139.6 MeV/c^2 Pion0: mass = 135.0 MeV/c^2 1) Apply conservation of momentum/energy to determine the...

Suppose you have two charged particles that interact by e.m. potential ##V(\vec{r_1},\vec{r_2})##, the total charge is conserved. Since there's a conserved quantity, it must exist a transformation for which the hamiltonian is invariant (Noether theorem). Let's be the operator ##U##...

Rg. Without air resistance, show the maximum height snow can reach is h_max=R+v^2/(2g)+gR^2/(2v^2) Solve using conservation of energy How do I start this problem? I assume all the initial kinetic energy ((mv^2)/2) from the spinning of the tire is translated to the gravitational potential energy...

Homework Statement A 2.0 kg ball moving with a speed of 3.0 m/s hits, elastically, an identical stationary ball as shown. If the first ball moves away with angle 30 ° to the original path, determine a. the speed of the first ball after the collision. b. the speed and direction of the second...

Hello, I recently posted a few conceptual questions regarding conservation of momentum. I'm processing the information more easily now, but I've hit yet another bump in the road. I've learned that in an inelastic collision in which "velocity is the same before and after the collision" the...

One thing that's been troubling me lately is the idea that a quantum experiment can start with the same initial conditions, but the outcome is probabilistic, not deterministic, and how this fits in with the conservation of momentum. I was thinking about the classic double-slit experiment, in...

Ok, so for the derivation of the Navier Stokes, the conservation of momentum through a control volume (CV) is Time rate of Momentum Change in CV = Time rate of Momentum Change into CV - Time rate of Momentum Change Out of CV + Sum of External Forces Why is Sum of External forces in there? I...

Question: A person wants to jump in the air. To do so, he has to crouch a distance C. He then has a push-off phase, where the he accelerates upwards by a distance C. At the end of push-off, he then achieves takeoff (airborne). The end of his takeoff distance is H, and H is the difference between...

Homework Statement Hi all! I have a very simple problem, which seems to get two different answers depending on whether you use conservation of angular momentum, or energy. Both quantities seem to be conserved: Initially we have a disk of radius a spinning about its center of mass at known...

when two objects collide some kinetic energy can be lost to heat, so some of the kinetic energy of the two colliding objects transfers to the individual particles of these objects. Does the same thing happen for momentum?

While reading the derivation of the formula \lambda' - \lambda = \frac{h}{ m_ec}(1-cos(\theta)) on Wikipedia, they point out that the momentum gained by the electron is larger than the momentum lost by the photon: $$ p_e=\frac{\sqrt{h^2(\nu-\nu')^2 +2h(\nu-\nu')m_ec^2}}{c} >...

Say you had two boats (a and b) moving past each other without colliding and a man moved from boat a to boat b. Is it correct that boat b would decelerate and boat a would accelerate due to the conservation of momentum

What are the conditions necessary for applying the conservation of mechanical energy or the conservation of momentum? Can we apply these anywhere or do we require specific conditions which have to be fulfilled for applying them?

Homework Statement A person stands on a platform, initially at rest, that can rotate freely without friction. The moment of inertia of the person plus the platform is IP. The person holds a spinning bicycle wheel with its axis horizontal. The wheel has a moment of inertia Iw and angular...

Are there elementary mechanics problems that illustrate the phenomena of time varying force fields and energies associated with such fields? Problems in elementary mechanics are often solved by using the principle of conservation of energy even though "the system" (of masses, pulleys, inclined...

I'm stuck on deriving the follow. Context: FRW Metric, dust dominated universe, use of conservation of energy-momentum tensor. I'll now state all the equations I can see are relevant. (But just in case the source is http://arxiv.org/pdf/gr-qc/9712019.pdf and it's eq 8.43). ## \frac{d}{dt}(\rho...

Hi. I'd like to find the maximal extension of a spring. The spring has a spring constant k. There's a mass m connected on the spring. From a height h above the initial location of mass m another mass M falls. When the two masses make contact they move as one. I found two methods to calculate...

when the gas effuse out of an insulated container, its velocity is given by \sqrt{\frac{2\gamma RT}{(\gamma-1)M}} (irodov's problem 2.42) This leads to the result that every mole of leaking gas has an energy of \frac{\gamma RT}{(\gamma-1)} whereas we know the energy contained in 1 mole of gas...

1. Homework Statement The question is to determine which decays are possible for: i) ##P^0 ->\prod^+ \prod^-## ii)##P^0 ->\prod^0 \prod^0## Homework Equations where ##J^p = 0^-, 1^- ## respectively for ##\prod^+, \prod^- , \prod^0## and ##P^0## respectively. The Attempt at a Solution For...

Homework Statement You are standing on your skateboard, which is at rest. Your friend throws a heavy ball at you. What should you do to minimize your velocity? A. Catch the ball B. Hit the ball back with the same velocity C. Neither, they both have the same effect. I would say (A). Because...

I'm a bit confused about how the work-energy theorem for a single particle can be extended into the general law of conservation of energy for the macroscopic system, particularly the point where we divide the kinetic energy of the system into macroscopic kinetic energy and internal kinetic...

Homework Statement Exam review question concerning 2 dimensional motion, the professor did not hand out an answer key and I am just looking for an answer check. A car launches at an angle of 30 degrees above the horizontal, off a cliff (50m), moving at an initial speed of 10m/s. Find the...

I have a question about conservation of energy in my system A heat pump allows you to move a quantity of heat with a smaller energy input. It is most efficient for small temperature differences. A heat engine allows you to convert a temperature difference into mechanical work. It is most...

Homework Statement Below is the question: I only have an issue with the last step of the problem. Why wouldn't you factor in the translational AND rotational energy of the ball and then solve for maximum height?

(This though came up while learning about band structure, so that is how I am going to explain it, but I think it applies equally well to a square well, for example). Say you have an electron at the Fermi level of an insulator. Then, you apply an electric field. No current flows, because all...

Keplers second law: An imaginary line joining a planet and the sun sweeps out an equal area of space in equal amounts of time. So this shows that the Earth would move faster if it was near the sun. Why? I have read that an abject will move faster if the mass has become smaller. If mass has...

Homework Statement Three smooth stones, A, B and C are initially at rest, in contact with each other on the smooth surface of a frozen lake (Figure 1). The masses of the stones are, to 3 significant figures, mA = 8.00 × 10^2 g, mB = 6.00 × 10^2 g and mC =2.50 × 10^2 g and the coefficient of...

this would be considered as an inelastic collision where (m1v1) + (m2v2) = (m1+m2)vf also the conservation of energy being (∆K +∆U)=0 i tried using the conservation of energy to find v2 as the variable we are looking for is Vf, the speed the bullet leaves the block, and v2 (velocity of the...

Homework Statement Homework Equations Momentum = mass x velocity The Attempt at a Solution Answer is A. when mass decreases, speed should increase for momentum to be constant. and when mass increases, velocity decreases. i could understand the graph up the before t2 with this. but at t2...

Homework Statement A uniform ladder having mass 14kg and length 3m is released from rest when it is in the vertical position. If it is allowed to fall freely, determine the angle Theta at which the bottom end A starts to lift off the ground. For calculation assume the ladder is a slender rod...

Homework Statement A load of 10 kg is pulled up a lubricated slideway, set at an angle of 30° to the horizontal, such that the load is accelerated from rest to a velocity of 1 m/s whilst traveling up the plane through a distance of 1 m. The frictional resistance to this motion is 10 N and g =...

Homework Statement QUESTION 1 :A stationary bomb explodes in space breaking into a number of small fragments. At the location of the explosion, the net force do to gravity is 0 Newtons. Which one of the following statements concerning the event is true? a) Kinetic energy is conserved in the...

Homework Statement A ball is thrown against a fixed wall where it bounces elastically. The mass of the ball is M and the velocity just before it hits the wall is U. Ignore the force of gravity in this question. a) Does the Principle of Conservation of Momentum apply to this situation? b) Obtain...

Homework Statement :[/B] There is a system, beginning from rest, with two masses, m1 and m2. M1 is on a table and attached to a rope that goes over a pulley (that is NOT massless)and attaches to hanging mass m1. Between m2 and the table there is a friction(kinetic) of 0.1 M1=10kg M2=30kg Mass of...

Homework Statement A 0.160 kg ball makes an elastic head-on collision with a second ball initially at rest. The second ball moves off with half the original speed of the first ball. a) what is the mass of the ball b) what fraction of the original kinetic energy gets transferred to the second...

Where, when, and why did the notion of conservation of energy become a law? I know that we are able to "invent" new means of "fixing" any apparent violations of this and further I understand that the new inventions of other energy forces have led us to new ways of seeing the world but I still...

Homework Statement m1= 3kg m2= 6kg v1 = 5m/s v2= 2m/s d = 3m DIAGRAM : http://gyazo.com/17b3126726b109256a35f65b86708bb0 Homework Equations Conservation of momentum: m1+v1 = m1v1'+m2v2' Conservation of elastic: m1v1^2+m2v2^2 = m1v1'^2+m2v2'^2 The Attempt at a Solution Now my attempt...

1. So the loop is known to be 12m in diameter (6m radius). Assume the car weighs 1250kg - how fast must the car go to clear the loop, and what will be its max G-forces endured? This was the question, which I have broken into 3 sections: a) Velocity at top of loop (done) b) Velocity at start of...