Energy conservation Definition and 434 Threads

Solve following problems by using energy conservation theory.. A car driving down a long hill. The engine is switched off, and the speed is constant. The hill has a drop of 1.00 m for each 25.0 m driven way. The car has mass 1020 kg. Calculate the total friction on the car. A cyclist...

I wonder of someone could help me understand something about emission and absorption of photons by atoms. I thought I understood the basics of this topic but yesterday a thought experiment occurred to me that seemed to violate conservation of energy. Imagine two stationary hydrogen atoms. Atom...

I'm a bit confused by vacuum "fluctuations" (I know there is nothing fluctuating since vacuum is lorentz invariant) and their interpretation/representation by Feynman diagrams. In a normal Feynman diagram, you have energy conservation at each vertex, so overall energy conservation is ensured...

In an experiment, one of the forces exerted on a proton is F = −αx^2i , where α = 14.4 N/m2. (a) How much work does F do when the proton moves along the straight-line path from the point (0.10 m, 0) to the point (0.10 m, 0.5 m)? (b) Along the straight-line path from the point (0.09 m, 0) to...

Homework Statement An engineer is designing a spring to be placed at the bottom of an elevator shaft. If the elevator cable should happen to break when the elevator is at a height h above the top of the spring, calculate the value of the spring constant k so that the passengers undergo an...

Hi, I am a little confused about the energy conservation of a pin ended free falling rod. When i try to derive energy conservation equation i am not sure including angular and linear velocity at the same time. I try to visualize the problem in the attached picture and put my derivation also...

So I feel really stupid asking this, because this is a very elementary physics problem and I'm well past this level of physics, but I don't understand what's going on here. Say we have a vertical spring with spring constant 100N/m. A 100N mass is placed on top of it. This will cause the spring...

Homework Statement A 10-kg block is released from point A. The track is frictionless except from the portion between B and C which has a length of 3.0 meters. The block travels down the track, passes through BC and first collides with a small block (m=2kg), then they travel together and later...

Homework Statement see link for a picture of the situation, http://i50.tinypic.com/n5g3z5.jpg Homework Equations (1/2)mv^(2) , (1/2)k*l^(2) The Attempt at a Solution Total energy of the system at the given point of time is mv^(2)/2+kl^(2)/2 = 0.6*100/2+100*0.25/2 = 30+12.5 =...

Thanks. I started a new thread, because I've seen what seemed to me a contradictory claim in Carroll's GR notes (Eq 5.38) - he says diff invariance is enough to get covariant energy conservation. I've never understood whether Carroll's claims and the ones in these papers are really...

Homework Statement A mass m hanging on a spring oscillates vertically. If the equilibrium point of the oscillation is a distance d below the relaxed length of the spring and if the amplitude of the oscillation is A, what is the maximum kinetic energy of the oscillation?[b]2. Homework Equations...

I have a quick question on Newton's third law. When a 100kg astronaut in space is holding a 100 kg rock and then pushes it away from him with 50 joules of energy (the kinetic energy put into the system) and a second astronaut (observer) is watching, sitting still relatively to the location...

Homework Statement Consider a mass connected to a spring of stiness k. (a) Use conservation of energy to write down a first order differential equation obeyed by the mass. (b) Find the time t for the mass to move from the origin at t = 0 out to a position x assuming that at t = 0 it has...

The cable of an elevator of mass M = 1640 kg snaps when the elevator is at rest at one of the floors of a skyscraper. At this point the elevator is a distance d = 36.4 m above a cushioning spring whose spring constant is k = 13600 N/m. A safety device clamps the elevator against the guide rails...

A man who was first standing runs from the point A.His speed is 40 m/s in B and 23 m/s in C,where the distance BC=30 meters..a) What work does the force of friction over the man ( m=60kg)? b) Find the max height reached by the man in the C level.. image here http://i.imgur.com/HVd7UH2.jpg I...

Homework Statement A mass m is laying on a frictionless table and is connected to a mass M with a nonelastic string going through the center of the table. At t=0 the m mass is at a r0 distance from the center of the table, and is moving at a v0 velocity in the tangent direction. Find the...

I have a question regarding X-ray diffraction and energy conservation. If one considers elastic scattering from a rod-like structure, the observed diffraction pattern will change as the sample is illuminated from different directions. For some directions the pattern will be point-like, and...

I'm pretty sure it cannot, but if I put a common bar magnet close to another magnet, they will move towards each other. I don't have much of a background in physics, but it seems to me that the kinetic energy is coming out of...nowhere. I can repeat this experiment as many times as I like but...

Given the Oscillator equation: \frac{d2s}{dt2} + \omega2s = 0 Show that the energy: E=1/2(\frac{ds}{dt})2 + 1/2\omega2s2 is conserved. Any help at all appreciated! Thankyou

Homework Statement Conservation of energy: looking for equations to solve the following Homework Equations A pendulum with length l = 0.50 m and with a negligible mass. The string is attached to a fixed point A and the pendulum swings in a vertical plane. The pendulum has a speed v = 2.15...

Homework Statement the sliding block has a mass of .850kg the counterweight has a mass of .420kg , and the pulley has a mass of .350kg with outer and inner radius .030m, .020m, the coefficient of friction is .250. the pulley turns the axle. the light cord does not stretch and does not slip on...

Homework Statement Consider the following situation: A 2.0 kg block is placed against a compressed spring on a frictionless 30° incline. The spring of force constant 19.6 N/cm is compressed 20 cm and then released. How far up the incline will the block go before coming to rest? Homework...

"Given a simple and violent chemical reaction { H + H → H2 + 5eV }. however when hydrogen atoms collide in free space they simply bounce apart. the reason is that it is impossible to satisfy the laws of conservation of momentum and conservation of energy in a simple 2 body collision which...

Homework Statement Assume the current in a series RLC circuit is given by I = ACω(sin(ωt) + \frac{α}{ω}cos(ωt))e^{-αt}. Calculate the energy stored in the circuit at t=0. Then calculate the energy stored in the circuit one-quarter cycle later, at t=\frac{\pi}{2ω}. Verfiy that the...

the charge(say positive) in figure induces negative charge on the disc and positive on sphere, the net force on charge is attractive towards the disc and is a function of position, now if someone moves the charge the amount of charge on disc changes accordingly and force changes its magnitude...

Must energy be conserved in a consistent Poincare invariant theory? It's not necessary in Newtonian physics. Are things different in special relativity?

Homework Statement In the image below, there are two balls of mass m attached to a massless rigid metal steam, which can rotate around the point A. Give the necessary velocity to be applied in the lowest ball for the system to reach the horizontal line. Do not consider any system's energy...

kindly help me understanding energy conservation in laser

Hi everyone, This is my first post here and I am really sorry for that question, but I have found the answer nowhere. Consider a mass at the Earth's equator that is static in the Earth's referential during an entire day. Put the Earth at one of its equinoxes to simplify the problem. Then...

I recall watching a documentary a while ago that explained the production of different force carriers. A bit that stuck in my head was that (if I remember correctly) W and Z bosons were able to violate the law of energy conservation. The energy to create these particles was apparently...

... C1.... C2-> P-> In the above illustration, P is a particle, C1 and C2 are detectors able to measure the energy/mass of a light pulse. C1 is at rest, P and C2 move horizontally to right with the same velocity. Let's say that P is actually a matter-antimatter pair that annihilates to...

The sphere with the mass 1 kg is released from point A without initial speed and moves without friction just like in the figure. a) Find the mechanic energy in point A Solution : E=mgh because v=0 b) Find the kinetic energy in B Using the law of the conservation of mechanic energy...

Consider a particle approaching a finite potential step or inside a potential well. As we know, the particle has a finite probability to penetrate into the region where E < V. The probability remains finite arbitrarily deep into the classically forbidden region. Suppose we set a detector far...

Homework Statement The spring in the figure has a spring constant of 1000 N/m. It is compressed 13.0 cm, then launches a 200 g block. The horizontal surface is frictionless, but the block's coefficient of kinetic friction on the incline is 0.220. What distance does the block sail through the...

I'm wondering about the Michelson interferometer and energy conservation. It seems like if one arm has an optical path difference that results in a pi phase shift relative to the other arm, then there will be complete destructive interference at the output port. Talking to some people, I gather...

Hi, I'm a EE PhD student working a little bit out of my area, and have just gotten stumped trying to figure out the transient dymanics of a relativistic electron moving past a discontinuity. My little thought problem came up from wakefield interactions of a relativistic electron in a waveguide...

Hello, I have a question, which is kinda stupid probably, but I cannot solve it for myself. Hence the fancy title. Imagine you have a point mass m near a more massive object M. Let's say there is some other force supporting the point mass, so it can stand still at r = \vec{r_0}. Point mass...

I was curious, why is energy conserved in elastic collision but not in perfectly inelastic collision? It said this in my textbook without giving any reason why.

Homework Statement A particle of mass m starts his motion from rest in the top of a inclined plane. It slides down the plane and enters a circular rail of radius R. (a) What's the minimum value of b for the particle not to Uma partícula de massa m parte do repouso no topo de um plano...

Hi guys, I was reading about quark confinement and came up with a doubt i can't find the answer to: You have to use energy to try to 'pull away' one of the quarks in a meson, right? And when you give enough energy, a new quark/anti-quark pair is created and that's why you never find only one...

A mathematical statement of energy conservation can be given using the continuity equation in terms of the total energy \frac{\partial}{\partial t}\iiint_V\epsilon dV+\iint_S \epsilon \mathbf{V\cdot dS}=0 where t is time, V is a velocity vector, V is the volume of the system, dS is a point...

Hey, here is the problem: The minimum distance of a comet from the Sun is observed to be half the radius of the Earth’s orbit (assumed circular) and its speed at that point is twice the orbital speed v(earth) of the Earth. The Earth’s and comet’s orbits are coplanar. Find the comet’s speed...

Homework Statement a mass M , attached to a horizontal spring executes SHM(simple harmonic motion) with amplitude A1 . when the mass M passes through its mean position then a smaller mass m is placed over it and both of them move together with amplitude A2 . the ratio A1/A2 is ...

Homework Statement A particle of rest mass m moving with speed c/2 decays into two particles of rest mass 2m/5 each.The daughter particles move in the same line as the direction of motion of the original particle.Then what are the velocities of daughter particle? Homework Equations...

Hello! Im working on a design lab but need a little help on making it simple enough to use materials you would find in a standard physics classroom. Purpose: To develop a testable question that examines the relationship between 2 variables governed by the law of conversation of Energy...

rotational motion, energy conservation problem URGENT please help Homework Statement A uniform rod of mass M=2 kg and length L = 2m is pivoted from its end. It has a point mass m=1 kg on its tip. It stars from rest at an angle of 30 degrees above horizontal. It falls under the influence of...

This is just a concept question. Say you have a spring arranged vertically with an object on the end of it. The spring is compressed.. At some point you, the system is released from compression. When calculating the velocity at which the object loses contact, I understand that you use the...

Consider the production of lift only as the reaction force from displacing a mass of air downwards. No matter the mathematical abstraction (Bernoulli, circulation theory) this Newtonian explanation must hold true. So now imagine a rectangular wing in a wind tunnel where the wing spans the...

Problem and Data three masses conected m1= 800g, m2 =1100g m3=1200g. m2 rest on a table of coefficient μ=0.345. m1 and m3 hang vertically over frictionless/massless pulleys. The system is released from rest. Whats the velocity of m3 after falling 60.0cm P.S "i know this system can be...

Hi, If we describe a beam splitter as follows: e^{ikx} -> \sqrt{T}e^{ikx} + \sqrt{R}e^{i\theta}e^{iky} e^{iky} -> \sqrt{T}e^{iky} + \sqrt{R}e^{i\theta'}e^{ikx} then \theta+\theta'=\pi is a condition to ensure conservation of energy according to my text. I tried working this out by taking...