Energy conservation Definition and 434 Threads

If on a taut string, we have a wave pulse traveling in the positive x direction with an amplitude A... simultaneously, from the other end we have a wave pulse traveling in the negative x direction with amplitude -A (i.e., it is faced downwards) At a certain time t, they will superimpose upon...

In 1993, a giant yo-yo of mass 480 kg and measuring about 1.9 m in radius was dropped from a crane 57 m high. Assuming that the axle of the yo-yo had a radius of r=0.1 m, find the velocity of the descent v at the end of the fall. I know that .5mv2+.5Iw2=mgh, but I don't have a clue how to...

Energy conservation in wave interference... Hey folks, Let's get right into the subject: we know that two waves of the same phase, frequency, type and wavelength traveling alongside each other interfere constructively and their intensity is 4 times that if it were one wave.. Now let's...

3.4kg rock starts at 25 cm on a plane with a 33degree angle. upon reaching the bottom the box slides along the horizontal. friction coeff is .19. how far does the box slide on the horizontal before coming to a rest? ok i need to use .5MVi2 + MGy1 = .5MVf2 + MGy2 + Ffrd first i need to...

Can somebody please check over my solution. I cannot figure out what's wrong. My final answer is not right. I think I may have an error with the signs of the point charges or may have a dumb calculation error. Thank youFour point charges, fixed in place, form a square with side length d. The...

A 7.94 kg stone is resting on a spring. The spring is compressed 10.2 cm by the stone. (a) Calculate the force constant of the spring. (b) The stone is pushed down an additional 28.6 cm and released. How much potential energy is stored in the spring just before the stone is released? (c)...

Hi, i've been doing a simulation using LJ model, but I'm having a troublesome time on figuring out, what's happening with the energy :rolleyes: This is the LJ potencial: E = 4\epsilon\left[\left(\frac{\sigma}{R}\right)^{12} - \left(\frac{\sigma}{R}\right)^6\right] but I've been using...

If Kinetic Energy is mv²/2 how come E=mc² is a valid equation.. wouldn't it have to be divided by two also because c represents a velocity? Thanks for any help.

I just did a lab on collisions. We used a something like an air hockey table but different. Anyways i have to determine whether or not momentum and kinetic energy are conserved. If there are no unknowns and you have the following information how would you determine if kinetic energy and...

A friend of mine came up with this idea that I would like to ask here. Just assume wormholes do exist and can be stable. Now put 2 wormholes over the surface of the earth. One 100meters above the ground and the other 1 kilometer straight above the first one. Link them so the first wormhole...

I was thinking about that question (what is energy) and I realized that I could easily understand what energy is and why it is conserved if I thought of it as the total force needed to get a mass to the position that it is in. For example: Kinetic energy - inorder to give a mass speed you...

Please help me, this is due tonight at 11 and I can't figure out what to do! " A 17 kg child descends a slide 3.5 m high and reaches the bottom with a speed of 2.5 m/s. How much thermal energy due to friction was generated in this process?" The equation should be: kinetic energy intiial...

In the attached picture below I am compressing a spring... In picture 2, I've compressed the spring a distance x and thus the elastic potential is 1/2 kx^2 and the total energy in the system AT THAT POINT is 1/2 kx^2 + mgh, isn't it? (m is the mass of the ball and h the height from my reference...

Hello, let us suppose that we have a quantum harmonic oscillator being in the first exciting state. It means that system has some definite energy E_1. Than we change force constant of of the oscillator. As a consequence eigen states and there energy are changed. I think that after this change...

A 10g bullet embeds itself in a 0.5kg block which is attached to a spring of force constant 36N/m. If the maximum compression of the spring is 1.5cm, find a)the initial speed of the bullet and b)the time for the bullet-block system to come to rest. can someone give me some help with the above...

i have a rotating disc. I have a tachometer and a sensor tape. Where should i stick the tape to measure the rpm correctly? How tachometer works? One more question. a rotating disc has kinetic energy. Why we study energy of a rotating. Now if i stop the rotating disc according to law of...

I would like, once again, trouble this community with "the only mistery" (as written by Feynman) of quantum mechanics, the double slit experiment. More specifically, I am exploring it in the recent version described by T. Marcella (Eur. J. Phys., 23 (2002)). For the benefit of those of you...

Hey, I was wondering if anyone can help analyze this problem with me. Here is the question. A swing seat of mass M is connected to a fixed point P by a massless cord of length L. A child also of mass M sits on the seat and begins to sing with zero velocity at a position of which the cord...

This is how highly complex but how is energy conserved in general relativity? Baez says that energy is conserved by installing energy pseudo-tensors into Einstein's field equations but is that it?

Two baseballs, each with a mass of 0.158 kg, are separated by a distance of 400 m in outer space. If the balls are released from rest, what speed do they have when their separation has decreased to 270 m? Ignore the gravitational effects from any other objects. I keep on using the conservation...

Hi, I had a question about reactions. I actually know how the baryon number, the lepton number, and the electric charge conservation works for reactions, but what i do not understand is the energy conservation. I searched the whole web for it, but there was no page where I could understand...

An elementary electron-> electron + gamma process can not occur by itself in the vacuum because if we assume the photon invariant mass zero and the electron invariant mass positive, energy and momentum can not be conserved at the same time. The delta E may be computed and from the energy time...

I'm going on 10 years since I got my (physics) degree, but I haven't done much work besides conceptual stuff in that time and it shows. :mad: Anyway, I decided to crack open my Modern Physics book from school and start working my way through it. The first few problems were OK, but I just...

I hesitated to ask this question because of all of the TeXing it would necessarily involve, but it's driving me nuts. Our prof gave us this question in the practice final, but I'm not posting it in HW help, because he's asking for a derivation straight from his notes. I already have the answer...

Hi there, after years of blissful unawareness, I suddenly managed to find a simple yet, annoyingly perplexing question regarding our old friend, the adiabatic process. Let's look at the facts. Any textbook will tell us that in an adiabatic process no heat is exchanged between the system and...

A large punch bowl holds 4.75 kg of lemonade (which is essentially water) at 20.0°C. A 2.00 kg ice cube at -10.2°C is placed in the lemonade. What is the final temperature of the system, and the amount of ice (if any) remaining? Ignore any heat exchange with the bowl or the surroundings. can...

1)A gardener pushes a 12 kg lawnmower whose handle is tilted up 37 degrees above horizontal. The lawnmower's coefficient of rolling friction is 0.15. How much power does the gardener have to supply to push the lawnmower at a constant speed of 1.2 m/s? not really sure where to begin with this...

Problem: A 3.30kg block is dropped from a height of 5.70m onto a spring of spring constant 3806 N/m. When the block is momentarily at rest, the spring has compressed by 32.0 cm. Find the speed of the block when the compression of the spring is 13.5cm. How I approached it: Calculate the the...

Say, you have a parallel plate ideal capacitor and you choose a rectangular path, one side of which lies inside the region of electric field and the side parallel to that lies outside it. The other two sides are obviously perpendicular to the field. If I take this rectangular path then how...

Suppose you have a teleski to climb a skiway of d=600m and θ=15º respect horizontal and μk=0.06 is kinetic friction coefficient in the cable. 80 skiers of 75kg (m=6000kg in total) each one wants to climb at the top at v=2.5m/s constant, What's the power that engine must provide in order to...

If a particle is launched with kinetic energy as it gets further from the mass (eg a planet) the kinetic energy decreases. However Potential Energy GMm/r also decreases the further you get from the mass. Where does all this energy go? :confused: Granted, the calculation U + K = 0 does give...

Why is kinetic energy conserved in an inelastic collision? (Dianalynn)

How much energy could be saved by users turning off their computers during long idle times? Were California's brownouts last summer due in large part to inactive computer electrical consumption? Is there an advantage to keeping computers on (overnight, say) that overrides immediate energy...

Assuming the roller coaster is towed to the top of the hill on the left-hand side of the diagram and released. How would the conservation of energy work. I know that at the top of the first hill there would be P.E. and as it gradually rolls down the K.E. takes over. But how about as it...