Energy conservation Definition and 434 Threads

Do temporary dipole moments require energy to form? I'm talking about Van der walls and London forces. If temporary dipole moments don't require energy to form then consider the free electrons in a metal plate, temporary dipole forces in the metal act on the free electrons causing them to gain...

Homework Statement A 2.0 kg ball moving with a speed of 3.0 m/s hits, elastically, an identical stationary ball. 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 ball after...

Define energy as E=T+U. For anyone using different terminology, by rheonomic (time dependent constraints) I mean that if a system has N degrees of freedom, the position vectors of each particle of the system are given by ##\vec{r}_i(q_1,q_2,...,q_n,t)##. Where ##q_i## are generalized...

Today, I discussed my friend about two rigid beams impact and assuming no energy loss in the impaction. As in the above figure, the upper beam move down with a uniform velocity ##v_c##, and hit a beam with ##0## velocity. After that the above beam will rotate and move away, which can be...

I have a block with a certain mass attached to a spring. I pull it and then release. Spring pulls block back. When spring is back to its relaxed position, is the velocity of the block positive or negative? Exercise does provide k, mass and x, but that's not where the error is comming from...

Homework Statement Two equal energy photons collide head on and annihilate each other, producing a u+, u- pair. The two particles have equal mass, about 207 times the electron mass. A) Calculate the maximum wavelength of the photons for this to occur. B) If the wavelength calculated in A) is...

Hi, so my question is along the lines of the following: Since the strong and EM forces are mediated by massless exchange particles, due to Heisenbergs uncertainty principle these forces are long range. Well, ok. But the weak force is mediated by W and Z bosons which are massive hence they can...

I have question that I've been thinking about for some time now, and that I can't get my head around. I an experimentalist without education in quantum field theory, and my quantum mechanics introduction courses were a long time ago, so bear with me please. As far as I understand, neutral kaons...

Homework Statement A ball (m=0.7kg) is dropped from a height (h=30m). The air resistance force is given by the formula F=kv^2 where k=0.0228 and v is the ball's speed. The ball bounces after a perfectly elastic collision. Calculate the maximum height the ball reaches after the collision...

Hi. Let's say two monochromatic laser beams superimpose in a single point in space in such a way that there's constructive interference. Because there's constructive interference there, the total intensity at that point will be larger than the sum of the separate intensities. Will this mean...

I know there has been a lot of threads on the forum about this topic, but my question is slightly different from the others. I have recently read this article by Sean Carroll (http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/); now, I'm completely aware (& convinced)...

I have a second order differential equation of the form (theta is a function of time): \theta ''=F\left(\theta ,\theta '\right) Turning them to two first order equations I get: \begin{cases} \theta '\:=\omega \\ \omega '=F\left(\theta ,\omega \right) \end{cases} And here's the algorithm...

A solid balsa cube of side length L = 16.0” and mass M = 8.60 kg is at rest on a horizontal table top. It is constrained to rotate about a fixed and frictionless axis, AB, along one edge of the cube. A bullet of mass m = 50.0 g is fired with speed v at the other side of the cube, at height a =...

Homework Statement A train is traveling in the x direction at a speed of v. On the train, a passenger is playing darts and fires a dart in the y direction with a speed of Uy. The dart hits the target and stops abruptly. What is the difference in the mass of the dart as observed by a person on...

Homework Statement Four weightless rods of length ##l## each are connected by hinged joints and form a rhomb (Fig. 48). A hinge A is fixed, and a load is suspended to a hinge C. Hinges D and B are connected by a weightless spring of length ##1.5l## in the undeformed state. In equilibrium, the...

1. Consider the situation shown in figure. Initially the spring is unstretched when the system is released from rest. Assuming no friction in the pulley, find the maximum elongation of the spring. https://drive.google.com/file/d/0B3FvaDRwJ2neQWtBU3JrazVTeEU/view?usp=sharing Homework...

Homework Statement a) Particle A decays at rest into two photons. Calculate, in terms of the rest mass of A, the energy and momentum of each photon. b) In a different reference frame, particle A is initially in motion such that its kinetic energy is equal to its rest energy. Find the momentum...

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...

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...

How do planets continuously rotate on their axis or revolve around stars ? Do the energy they consume for this continued motion gets expelled as heat ?

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...

Homework Statement You've taken a summer job at a water park. In one stunt, a water skier is going to glide up the 2.0-m-high frictionless ramp shown, then sail over a 5.0-m-wide tank filled with hungry sharks. You will be driving the boat that pulls her to the ramp. She'll drop the tow rope at...

Homework Statement A possible decay mode a of a positive Kaon in the production of three Pions as shown below:. K+ → π+ + π+ + π− Whats is the maximum Kinetic energy that anyone of the pions can have? The kaon is a rest when...

Homework Statement I am doing the rotational motion experiment with a rotary disk that has three spindle sizes. A string goes around the spindle and is connected to a hanger. I calculated my ratio as a percentage of total final KE to decrease in potential energy and it comes out to be around...

Homework Statement With what initial speed must an object be projected vertically upward from the surface of Earshot rise to a maximum height equal to Earth's radius? (neglect air resistance.) Apply energy conservation. Homework Equations ##E_{k_1}+E_{g_1}=E_{k_2}+E_{g_2}##, however since...

Homework Statement In classical electromagnetism, an accelerated charge emits electromagnetic radiation. In non-relativistic limit, where the velocity of the electron is smaller than c, the total power radiated is given by the Larmor formula, to wit P=2/3*e2*a2/c3, where a denotes the...

Homework Statement Homework Equations Conservation of energy, F=ma The Attempt at a Solution (a) By the conservation of energy, we use points A and C as the initial and final, ## \frac{1}{2} m v^2 - \frac{1}{2} m 2.5^2= (m)(g)(9.76) \Rightarrow v = 14.1 m/s ## (b) Since ## W_{nc} = \Delta...

There are two disks of the same size and mass. A 5N force acts through the center of the first and another 5N force acts through the bottom of the other. The forces both point to the right. According to what I have learned, the linear momentum of both objects will be the same, but the second one...

Homework Statement If two bodies, each of mass M and radius R, initially r (r>>>R) distant away from each other start approaching each other with negligible speed then what is their speed which they collide?? Homework Equations The Attempt at a Solution initial energy,IE = (-G m^2) / r final...

Energy conservation violation First of all, I would like to say that this model is NOT a perpetual motion. It will stop eventually. What I want to say here is that the output useful work seems to be greater than input energy My system consists of 2 elements. Each element is a cylinder put on...

Homework Statement The pendulum shown (http://puu.sh/chwMZ/90f4b96fb1.png ) swings freely, turning around at a height of 10 cm above the lowest point in its swing. It has an unknown mass, but air resistance can be ignored. a) Use energy conservation to find its speed at the lowest point of...

Homework Statement Use energy conservation to answer the following question. A mass is attached to one end of a massless string, the other end of which is attached to a fixed support. The mass swings around in a vertical circle as shown. Assuming that the mass has the minimum speed necessary at...

I am currently looking facing a problem concerning a spring slider system. The system consists of a electro engine that pulls on a spring with a constant velocity. The spring is attached to a block that sticks to the surface, but after a certain force is applied (by the spring) starts to slip...

Homework Statement A 1300-kg car is backing out of a parking space at 5.0 m/s . The unobservant driver of a 1700-kg pickup truck is coasting through the parking lot at a speed of 3.2 m/s and runs straight into the rear bumper of the car. (a). What is the change in internal energy of the...

Consequences of Energy conservation in a FLRW spacetime This entry uses the local energy conservation law to derive an equation that can be used, together with the Einstein field equation, to derive Friedman's equations for the dynamics of a homogeneous, isotropic universe. The energy...

Homework Statement Two receivers, d=5 [meters] apart, are recording an air wave signal. The air wave travels in v=330 [m/sec] and coming from one side of the receivers. The air wave contains all the frequencies between 10 [Hz] and 200 [Hz]. a) If we sum up the recorded signal from the...

Of course I am sure this is not a paradox but rather a problem in my understanding of the situation. But this question is bogging me, and I haven't found a satisfying explanation yet. Suppose you are floating in space, in an inertial frame. An object much more massive than you is moving with...

Hey everyone, A meager pea brain (me) is in need of some help from you fine physics gentlemen. This is a concept I've spend a lot of time pondering on (more than I would like to admit). Imagine a rod of uniform density in free space. If you apply impulse onto the center of mass then it...

What is the relationship of conservative & non-conservative forces to the conservation of energy? What differs with the two? Energy in each case...?

Question on Energy conservation -- Car pushing on air column Homework Statement An automobile moving through the air causes the air velocity to decrease and fill a larger flow channel. An automobile has an effective flow channel area of 3 m^2. THe car is traveling at 90 k/h on a day when the...

If three circular or ring type magnets are placed such tnat centeral magnet is having its center at origin and other two are placed at its aperture repeling each other but they are just at enough distance such that the whole system is in equillibrium, placed on surface having friction. If i...

Thank you for helping me 1- One end of a rubber band is tied down and you pull on the other end to trace a complicated closed trajectory.If you were to measyre the elastic force F at every point and took its scalar product with the local displacement F→*r→,and then summed all f these . What...

Consider the following setup (see illustration above): a mass m is connected to a circular section of a rail by means of a rod (with negligible mass) of length r, where r is the radius of the rail. The connection point P of the rod can move frictionless along the rail but is mounted such that...

When Earth pulls a mass with gravitational force why does the energy of the earth-mass system decrease? Isn't work just transfer of energy meaning constant overall energy?

Hello I just read this http://io9.com/scientists-just-created-some-of-the-most-powerful-muscl-1526957560 where they explain a new type of revolutionary artificial muscle. The principle of operation is very simple: when a material gets hotter, it contracts and generates a force. I already...

Homework Statement A ball of mass M = 0.320kg is connected by a light but rigid rod of length L = 0.770m to a pivot and held in place with the rod being vertical. A wind exerts a constant force F to the right on the ball. The ball is released from rest, and the wind makes it swing up to a...

Homework Statement A light spring is fixed to the bottom of a vertical tube.A ball is released from rest at a height h above the upper end of the spring as shown.After rebounding several times the ball eventually comes to rest and stay on top of the spring.Assume all contact surfaces are...

Here's a thought experiment : Two identical spherical waves exactly 180 degrees out of phase destructively interfere throughout all of space. Is the energy contained in them just lost ?

Homework Statement A particle P is free to slide on a smooth wire which has the form of a helix, with a position vector given by: r((t)) = a cosθ(t)i + a sinθ(t)j + bθ(t)k The particle is released from rest at the point (a, 0, 2∏b). Using energy conservation for conservative...

Homework Statement http://imgur.com/xIckJqW A block of mass m rests on a plane inclined at an angle θ with the horizontal. A spring with force constant k is attached to the block. The coefficient of static friction between the block and plane is μs. The spring is pulled upward along the...