Conservation of energy Definition and 1000 Threads

Hello. I'm new to physics, and the problem I have seems so basic, mathematically speaking. I'm just failing to grasp exactly what is being asked. If I can find that, I believe I can find the answer. Here it is: 1. Homework Statement Let A = x2ˆx + y2ˆy + z2ˆz Consider the parabolic path y2 =...

Hello! I am just stuck on one part of this question and would be grateful for any help. Question A small block of ice slides from rest from the top of an inverted frictionless bowl of radius R (above right). How far below the top x does the ice lose contact with the bowl? Equations mgx =...

Homework Statement A ball of mass m falls from height hi to height hf near the surface of the Earth. When the ball passes hf, it has a speed of vf. Ignore air resistance. Consider the system T which consists of the ball only. Write an expression for each of the following quantities in terms of...

Homework Statement I am given that an object of mass m has an attractive force F=-A/x^2 acting on it, where A is a constant and x>0. I need to find the potential energy. After i need to suppose initial conditions (x0, v0) such that total energy=0. I need to find the trajectory x(t) with v>0...

Homework Statement A mass is suspended from a crane by a cable of length L. The crane and the mass is moving at constant speed V. The crane stops and the mass on the cable swings out. What is the angle that the mass swings? If the angle is 50 degrees and L=6m, what is the initial speed of the...

Homework Statement A dumbell is leaned vertically on the wall. After it is deviated with some angle θ, dumbell starts sliding. Determine the angle between the bar and the horizontal face (floor) when the upper mass starts to fall. Homework Equations E = E'The Attempt at a Solution [/B]...

Homework Statement Show that the largest possible change in the kinetic energy , ##\Delta E_{kin}##, of a particle of mass ##m## running into another particle of mass ##M## at rest in the lab coordinate system is \Delta E_{kin} = \frac{-4AE_{kin}}{(1+A)^{2}}, where ##A = \frac{M}{m}##...

I expect that others have already asked and answers this question but I could not find it with Google searches. My thought of this apparent antenna reciprocity violation is per below. Since antenna reciprocity states that an antenna will have same characteristics whether used a transmit...

Homework Statement Homework Equations d/dx The Attempt at a Solution d/dx (T) = d/dx(1/2mx'2) = mx'' d/dx(U) = d/dx(1/2kx2) = kx' ≠ kx It's probably me who made an error because I know that that equation (2.3) is the one I should be getting, but I don't understand how they did it because...

How do conservative forces exactly conserve mechanical energy while non conservative forces do not. Also why is potential energy defined only for conservative forces?

Homework Statement Pole-vaulting is a fantastic example of energy being converted from one form to another. A pole- vaulter 1.7 m tall runs at 30 km/h (8.4 m/s) with her pole before starting her jump. The kinetic energy she generates is converted into elastic potential energy of the pole...

I read that since CPT-symmetry is not broken, and CP-symmetry is, T-symmetry must also be broken, is that correct? If that is correct, does that mean that energy isn't conserved?

1. A car accelerates 1800m down an incline of 1 in 4 at 0.4ms^2. The car has a mass of 4,000kg and the resistance to motion is 400N Determine: a) The Tractive effort required by using D'Alemberts principle b) The Tractive effort required by using the conservation of energyHomework Equations...

I am still in secondary school so I probably shouldn't think about things this complicated (at least that's what it seems to me, complicated), but please correct me if I'm wrong. If I recall correctly, the position of an electron is never certain, and always based on probability, unless...

Hi everyone Would like some help here. If I draw a control volume across a valve that I can control the flow area to, and I know the temperature and pressure upstream of the valve, I will know its enthalpy:in. High temperature liquid going through this valve supposedly changes to steam due...

for my physics class a was working on a formula about conservation of energy could you guys tell me if it is somewhat right and stuff i forgot about =constant/s so this is my try making a formula about the total energy in the universe

Homework Statement Homework Equations PE = mgh KE = 0.5mv^2 WD = F * s The Attempt at a Solution Its part i. I understand the solution when you look at the whole system. You do not need to consider the tension in the string because they cancel out, but I want to be able to do it just...

e few days ago i talked with my teacher about the energy in the universe being constant. but we were completely confused when we came to the concept of: "because of the universe expansion everything moves away from each other. and the same goes for the wavelenghts in light. because of the way...

Hello all, I can understand the mathematics of this phenomena First, one can solve the Euler equations of motion numerically, using Runge-Kutta and plot the motion. Also, the path of the angular velocity vector will like on the kinetic energy ellipsoid and the angular momentum vector...

How does friction lose energy when the conservation of energy law doesn't allow energy to be lost ?? Sorry if this is a stupid question I have tried googling but can't find much to help.

Homework Statement Two identical twins, A & B, are riding identical bikes up the same hill, both at constant speed. Twin A takes 20 seconds to climb the hill, while twin B takes 40 seconds. a) Neglecting all forms of friction, which twin consumes more energy? b) With friction, which twin...

Homework Statement The period of a comet is 75.8 years. The perihelion distance is 0.596 AU (1 AU = 1.5 ⋅ 1011 m). The velocity at perihelion is vp = 5.45 ⋅104 m/s. a) Find the length of the major semi-axis of the elliptical orbit. b) Find the aphelion distance and the velocity at aphelion...

Imagine a hoop with mass M and radius R that will only roll without slipping on the floor. Place a point object with mass m on top of the hoop and then the system starts from at rest. Question: where does m leave M? If one fixes the hoop or let the hoop slide, solutions can be found using high...

A measurement of an observable that does not commute with energy will generally cause a change in the expectation value of the energy. Is there a clear formalism to describe how energy is conserved overall?

Homework Statement A ball rolls down an incline plane without slipping. What is the ratio of its angular velocity at h/3 to its angular velocity at 2h/3? 1) 1:2 2) 1:sqrt(2) 3) 1:1 4) sqrt(2):1 5) 2:1 Homework Equations Conservation of energy with provisions for rotational and...

During gravitational collapse, gravitational potential energy of the gas is converted to its internal kinetic energy so the internal energy of the clous of gas is said to be increased But isn't gravitational potential energy included in the internal energy? Shouldn't the internal energy remains...

I came across this issue a while ago, when spacetime expands, then energy doesn' seem to be conserved? But does not that violate the law of conservation of energy? I don't get it, how can spacetime expansion happen without energy issues? Thanks in advance

This thread is about a topic that unexpectedly came up in my thread titled "Contradiction between Cosmos and what someone here told me?". I will subsequently call that thread "Contradiction" for brevity. I am not sure if this thread belongs on the Quantum Physics forum or the chemistry forum...

So if a ball is rolling down a ramp and not slipping, you have two torques... the mg*sin(theta) portion of gravity and the (mu)mgcos(theta) for friction. My question is this: Does this friction force remove energy from the ball? (I know it affects the balls rotation but this is just changing...

Homework Statement Suppose we drop a lead ball of mass M into water of mass m from a height h and allow everything to settle down. What is the temperature change of the water? Assume that the container is well insulated. Homework Equations Potential Energy = mgh dU = mcdT where dU is the...

Homework Statement A rigid body is made of three identical thin rods, each with length L = 0.530 m, fastened together in the form of a letter H, as suggested by the figure here. The body is free to rotate about a horizontal axis that runs along the length of one of the legs of the H. The body...

This isn't about a specific physics problem, but rather a question: Given I have a ball or cylinder rolling smoothly along some path, is it generally true that mechanical energy is conserved? I.e. if ##E_mech = K+U = K_{trans} + K_{rot} + U##, then ##\Delta E_mech = 0##? I have been able to...

Homework Statement [/B] The coefficient of friction between the block of mass m1 = 3.00kg and the surface in Figure P7.22 is μk = 0.400. The system starts from rest. What is the speed of the ball of mass m2 = 5.00 kg when it has fallen a distance of h = 1.50m? Homework Equations This is in...

The question asks: Uranium nuclei are unstable and decay by emitting a helium nucleus, which contains two protons and two neutrons. Suppose the original nucleus has 92 protons and 146 neutrons before it emits the helium nucleus, and that the helium nucleus has an knknown speed as it departs from...

Hi all, I'm having trouble working out how much energy will have to be dissipated in a test rig for a nail gun. From previous testing, I know that a test slug fired from the gun has a mean energy of 100J. I now want to design a test rig which can fire the gun repeatedly for 100,000 shots. I...

I am doing a lab in my senior physics class (IB HL Physics 3-4) and I am very confused about a relationship that I found. For my experiment I dropped a racquetball from different heights and then used video analysis to find the height of the ball on its final bounce. I used this data to...

Homework Statement Jack (mass 59.0 kg ) is sliding due east with speed 8.00 m/s on the surface of a frozen pond. He collides with Jill (mass 46.0 kg ), who is initially at rest. After the collision, Jack is traveling at 5.00 m/s in a direction 34.0∘ north of east. Ignore friction. Homework...

1. Homework Statement I'm working on the second part of this question and I want to find the initial speed before P strikes the barrier. So I used principle of conservation of energy, K.E at Equilibrium position + elastic p.e. at Equilibrium positon = K.E just before it strikes the barrier +...

Hi PF, I've got a very trivial conceptual question regarding the conservation of energy with respect to thermodynamics and heat transfer that I can't seem to figure out. Suppose I have an electric heating element with a 240 volt, 30 amp supply, in contact with a solid volume of an arbitrary...

Just signed up, hi everyone! 1. Homework Statement A man weighs 150 lb, and attaches a bungee cord having a stiffness of k = 500 lb/ft, to his feet. If he jumps from rest off the side of a bridge, determine the required unstretched length of the cord so that he can just touch the surface of...

1. Homework Statement For part (iii) , I used the principle of conservation of energy, K.E of the 2 kg particle after collision + E.P.E = K.E of the 2 kg particle at the furthest distance away from A + E.PE, But the solution for this question did not include the E.P.E of the string...

By squeezing a spring until it coils up, it then has more potential energy. So it will then have more mass, because mass is energy. So doesn't that violate the law of conservation of energy. The spring has more energy and mass after its squeezed than when it wasn't squeezed?

Hello, I have a simple question. Has the discovery that some neutrinos change their flavor posed any issues with conservation of energy?! How has this been solved?! Thank you.

The thrust of an airplane changes the speed of the airplane, or you can look at it as it is increasing the airspeed relative to the airplane. The airspeed across the wings is only as much as the thrust allows it to be. The airspeed across the wing is what produces thrust, and I realize how it...

When a particle (or any objects) accelerates when acted upon by fundamental forces, what is happening to the amount of energy in that particle? A large example would be an asteroid in space caught by Earth's gravity and accelerates toward Earth as a result. The fundamental forces here can be...

Homework Statement a 5.0 x 10^5kg railroad car moving at 8.0m/s. collides with a stationary railroad car of equal mass. after the collision the two cars lock together and slide forward. What is the final velocity of the wrecked cars? using conservation of energy M1 = 5.0 x 10^5 kg M2 = 5.0 x...

Homework Statement A spherical object is dropped from an elevation great enough such that it will achieve terminal velocity for some period of time before hitting the ground. Once terminal velocity is achieved what is gravitational potential energy converted to. Homework Equations Ug = mgh Ke...

Homework Statement An 8.00-g bullet is fired horizontally into a 9.00 kg block of wood on an air table and is embedded in it. After the collision, the block and the bulet slide along a frictionless surface together with a speed of 10cm/s. What is the initial speed of the bullet? M1 = 0.008kg...

Imagine I have a rocket with a certain amount of energy stored as chemical energy, let's say its 10Js, that exhausts itself after 5 seconds. If I attach this rocket to a (relative to an observers frame) stationary cart in such a way that it pushes the cart, it will add 10J of kinetic energy to...

Let's say you have 2 100% efficient reflective surfaces exactly parallel to each other. If you theoretically managed to place photons at exactly 90° angle of incidence. So this beam of visible light (and I want to stress that) is going to stay there as long as there is no interaction, the beam...