Conservation of energy Definition and 1000 Threads

The arrow is following projectile motion to the target when released from an archer's bow. v vertical = 10ms^-1 v horizontal = 50 ms^-1 resultant v = √2600 mass of arrow = 20*10^-3 I attempted to use F avg = mΔv/Δt to calcualte the average force where Δt = 5*10^-3 /...

This is more like a theoretical question of my own than actual homework. Say there is a circuit with a current source and an inductor. There is a current ##i(t)=at## going through the inductor. We now place a new circuit with an inductor and a resistor next to it. The current ##i(t)## causes a...

The solution is an application of the law of conservation of energy. Start with equation (1). The masses are in equilibrium and are not accelerating. This implies that ΔK = 0, because the kinetic energy will not change without acceleration. Thus, we are left to find equation (2) in terms of θ...

If we have a two dimensional measurementbasis, then we have two possible outcomes of the measurement. Now I figured: considering the law of conservation of energy, if one particle goes in, one and only one can come out. So outcome "both results simultaneously" cannot happen, for that would...

The vacuum density, or the zero point energy, of a field, doesn't change as space expands, it remains constant. But, aren't particles and virtual particles just fluctuations of these fields? Meaning as space expands, more and more particles are being created, violating conservation of energy?

I have tried using Conservation of Energy but I'm getting incorrect answer.

Hola! So my first approach to this is use both the conservation of energy and momentum equations since collision between the first two objects are elastic. Let the 3 blocks be a,b and c (from left to right) Does this means the following: whereby ##v_{a} ##= speed of block a after collision...

It is said that for a particle in a box the energy is in a superposition. If indeed that is the case what happens when a measurement is made where does the excess energy go. Of course, that is based on my understanding is that superposition is a real physical and not platonic.

If someone could advise what I've done wrong it would be much appreciated. How have they eliminated the initial and final for y, and simplify only to y? Also, how did they simplify to a positive 2? What algebraic steps have I missed? Thanks for your help.

Dear all, I am back with another Spring problem. I have tried to use the insights I gained from your help last time: https://www.physicsforums.com/threads/find-v-x-of-a-mass-suspended-from-a-spring.972942/page-3#post-6190934 I figured I start with calculating the new equilibrium by ## x...

Could anyone explain me in simple words what is being said in this topic from this book (great book and author btw)... i don't understand after it starts talking about perpetual motion and lifting and lowering of weights.please explain in simple words. okay someone said to add more details to my...

2 bodies that have distance d between them are distancing from each other because Hubbles law. at time t=0 distance between them was d(0) and speed between them was 0. If no force interacts with them then distance is increasing by rate ##\frac{\partial d}{\partial t}=H_0*d## Is it correct...

The question asks for a bunch of stuff, but I have everything except part d down. a) Setting the mass of lemons as m1, I used m1*gh = 1/2mv^2, solving for v of the lemons as v = √2gh, where h is the height at which it is dropped. Then, I used COM and had this equation (not 100% sure if right)...

I write Conservation of Energy: Potential Energy loss(change): U = m g ##\Delta##h = m g (R+r) (1-cos##\alpha##) kinetic Energy gain(change): K = (##\frac {m v^2} 2## + ##\frac {I \omega^2} 2##) + (##\frac {M v_2^2} 2## + ##\frac {I_2 \omega_2^2} 2##) U = K m g (R+r) (1-cos##\alpha##) =...

Let v be the speed of the block and x elongation of the spring beyond the equilibrium point. Initially, v = 0 and x = 0. At the maximum elongation, the block also has v = 0, it has moved a distance equal to x (parallel to the plane) and the variation of height is equal to -x⋅sin(53°). W(FNC) =...

I feel like it would go on the side of the energy the object has where it starts - an object dropped off a cliff would be modeled U - W = K but an object thrown upwards from ground level would be K - W = U. I am not sure though.

I am confused about the cosmological constant and dark energy. In the most accepted theory, energy is created as the vacuum of space expands. This contravenes the conservation of energy. The law of conservation of energy does not hold in curved spacetime but isn't our universe flat spacetime ...

Solving using Linear Momentum: M vb2/2 = M g 2L vb = 2√(g L) m v = m v/2 + M (2√(g L) ) v = 4 M √(g L) / m Note: I see from the answers - that this is correct. -------------- Next, I tried to solve it via Energy conservation point of view. M vb2/2 = M g 2L vb = 2√(g L) m v2/2 = m v2/8 + k...

If we have an object in space (deep space where it is under no other gravitational influence) and we push it a little so that it gains some velocity and after some time comes into the influence of a planet's gravitational field and crashes on it. Where is that energy from the crash coming from...

Here are the two questions I want to compare: 1. A student of mass 62 kg stands on an upholstered chair containing springs, each of force constant 2.4 × 103 N/m. If the student is supported equally by six springs, what is the compression of each spring? 2. A 0.20-kg ball attached to a vertical...

A while back I thought of an issue with parallel charged plates. Imagine this: a set of opposite charged resistive plates with holes in the center. In theory, there is a finite amount of energy required to push a positive charged particle through the hole in the positive plate (in theory it...

Homework Statement A 39,000 lb truck A and a 3968 lb sports car B collide at an intersection. At the moment of the collision, the truck and the sports car are traveling with speeds vA = 70 mph and vB = 30 mph. Assume that the entire intersection forms a horizontal surface. Letting the line of...

Homework Statement A block is suspended by an ideal spring of the force constant K. If the block is pulled down by applying a constant force F and if maximum displacement of the block from its initial position of rest is X then, find the value of X. Homework Equations mg + F = XK + K(mg/K)...

When I first learned about these subjects, I did what was intuitive to me and treated particles as if they carried potential energy. I would do this similarly for rigid bodies where I would also treat them as a particles with their body's mass at the center of mass. This wasn't helped by...

Homework Statement A person is bungee jumping from the top of a cliff with height H. The un-stretched length of the bungee rope is L. The person comes to a stop just before hitting the ground. The length of the cord is equal to H(amax-g)/(amax+g), where amax is the maximum acceleration upward...

Homework Statement A ski starts from rest and slides down a 22 o incline 75m long. Coefficient of friction is 0.090. What is the skiers speed at the base of the inlcline? Use energy methods Homework Equations PE=mgh KE=mv2/2 W=Fd The Attempt at a Solution Since mass was not given I did PE=KE...

The conservation of energy states energy can never be created nor destroyed, and the amount of energy in a system is always constant. I'm just curious, say if a billiard ball just suddenly started moving without any other object making it do so, (kinetic energy was created), if it also suddenly...

My question: Consider an isolated system consisted of a ball, and a bucket of water. The ball is released from height, H above a bucket of water. The initial temperature of the water-bucket system and the ball are T1 and T2 respectively. What will be the final temperature of the water after the...

Wald and Zoupas discussed the general definition of ``conserved quantities" in a diffeomorphism invariant theory in this work. In Section IV, they gave one expression (33) in the linked article. I cannot really understand the logic of this expression. Would you please help me with this?

1. A spring is suspended from a ceiling and a 256g mass is attached to it and pulled down to stretch the spring by 18.2cm The mass is released and travels through the equilibirum position with a speed of 0.746m/s. Calculate the force of the spring constant Solution Et= Et' Ee = Ek + Eg 0.5kx^2...

Hi, I have a general question to pendulums. I hope it is ok to post it in this format. Please accept my apologies for my poor English. Homework Statement : As a general Example: I have a Pendulum of length L with Angle Theta as maximum displacement. I know how to solve these problems. Find...

Homework Statement A rocket burns out at an altitude h above the Earth's surface. Its speed v0 at burnout exceeds the escape speed vesc appropriate to the burnout altitude. Show that the speed v of the rocket very far from the Earth is given by v=(v02-v2esc)1/2 Homework Equations KEf-KEi=Ui-Uf...

Homework Statement You are driving with your car (of total mass: 1.2tonnes) with a speed of v=50km/h, until you see an obstacle. a) What is the kinetic energy of the car? b) When you start to brake, there is still 15m until the obstacle. What must be the size of the friction coefficient (µ)...

Homework Statement Please look at the attached screenshot. Homework Equations Assuming the ramp is frictionless, Ei = Ef and thus mgh = KE ( = 1/2mv^2, which isn't really necessary here) The Attempt at a Solution I'm okay with all other examples except for A and C. From the answer template...

Homework Statement PROBLEM A: A small cube of mass m slides down a circular path of radius R cut into a large block of mass M. M rests on a table, and both blocks move without friction. The blocks are initially at rest, and m starts from the top of the path. Find the velocity v of the cube as...

I have read that conservation of energy is not a meaningful concept in an expanding universe cosmology. See here http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ However I have also heard the if the net energy os the universe is zero then it can have a vacuum genesis...

Let's say both battery have the same charge capacity of 3Ah Battery A has voltage of 3V and B has voltage of 6V. Battery A is completely discharged while B is completely charged. If I charge battery A with battery B, wouldn't B be completely drained because they hold the same amount of charge...

I would like to understand better about the conservation of energy in GR. Let us think of infinitesimal vacuum volume dr\ sin\theta d\theta d\phi around the star in center. Light emitted from the star hit the bottom surface, r, of the volume. Say violet light photons hit the area 1 photon/1...

Homework Statement A toy gun is pointed toward the sky. A Styrofoam ball of mass 10g is at rest against a spring compressed 2cm. The spring is released causing the ball to move upward through the air to a max height of 1m. The air exerts a frictional force of 0.35N on the ball. What is the...

Homework Statement A horizontal spring with a constant of 700N/m is compressed 2cm. A ball of mass 200g is placed in front of the spring. The spring is released. The ball slides along a horizontal track for 10cm while experiencing a frictional force of 0.75N. What is the velocity of the ball at...

Hi I'm wondering how when a charged particle is accelerating it both emits energy in the form of em radiation while also gaining kinetic energy. All of that energy comes from the thing accelerating the charged particle, yeah? Is that necessary, like it is not possible to give a charged particle...

We experimented with the Maxwell's wheel today and at the end we were asked about why does this apparatus stop since there is conservation of energy. I did some research and apparently there is a type of friction called "rolling friction", wikipedia defines it as "the force resisting the motion...

In the equation 7.4, the author is taking v0=√(C/M)*x, and I don't get where does that come from. I would really appreciatte your help, thanks.

http://www.animations.physics.unsw.edu.au/jw/rotation.htm#rolling I have set up an apparatus similar to what the above link says (the first bit about brass object with shaft). So basically, the shaft is in contact when the brass is first rolling, then it suddenly accelerates when the edge of...

A point mass in an uniform circular motion is continuously changing the velocity direction. To do it, it continuously need force (energy). If we don't give any energy to the system it will anyhow continues its uniform circular motion. How it's possible, who gives the energy ? (It's seems a...

Homework Statement The objects are set free from the scenario shown in the attached image. Their masses have been given and they are under the effect of gravity. The length of the string has been shown in the figure. If the two blocks cross each other, then we need to determine the minimum...

Recently looked at why temperature flows from high Temperatures to Low temperatures.Essentially it was laid on two Fundamental Assumptions: 1.Energy is conserved in the isolated system 2.Entropy in isolated non quasi static systems will always tend to increase. Lets take a brief look at...

I always think about entanglement as pure conservation of energy and conservation of angular momentum. In fact I see that only conservation of energy is non-local, and that quantum objects have nothing to do with non-locality, for example you can entangle 2 atoms that have never interacted with...

The problem is attached in the photo. The correct answer, according to the teacher's solution, was obtained using conservation of energy. Initially I tried using Newton's law/kinematics and got the wrong answer. Why didn't this work? Can you ever use Newton's law/kinematics to solve pulley...

Hello, I was recently given the task to find experimentally the moment inertia of a sphere. I thought of rolling the sphere down an inclined plane and applying conservation of energy to the sphere. The equations i came up with are: mgh = 1/2mv2 + 1/2Iω2 solving for v^2 we come up with the...