Conservation of energy Definition and 1000 Threads

Question: A person wants to jump in the air. To do so, he has to crouch a distance C. He then has a push-off phase, where the he accelerates upwards by a distance C. At the end of push-off, he then achieves takeoff (airborne). The end of his takeoff distance is H, and H is the difference between...

Homework Statement Hi all! I have a very simple problem, which seems to get two different answers depending on whether you use conservation of angular momentum, or energy. Both quantities seem to be conserved: Initially we have a disk of radius a spinning about its center of mass at known...

Suppose you have a source of electron antineutrinos, and you arrange your apparatus so that a billion billion billion of them collide directly with a black hole. In principle, you could measure the change in momentum and energy from that occurrence. Suppose you did that the next day. According...

Are there elementary mechanics problems that illustrate the phenomena of time varying force fields and energies associated with such fields? Problems in elementary mechanics are often solved by using the principle of conservation of energy even though "the system" (of masses, pulleys, inclined...

Hi. I'd like to find the maximal extension of a spring. The spring has a spring constant k. There's a mass m connected on the spring. From a height h above the initial location of mass m another mass M falls. When the two masses make contact they move as one. I found two methods to calculate...

Homework Statement A small ball of m=1kg at height hp = 8m at point p, is given an initial horizontal speed vp = 10 m/s. It slides over an uneven frictionless surface. What is speed vq of the ball at height hq = 3m at point q? Homework Equations Ui + KEi = Uf + KEf The Attempt at a Solution...

I'm a bit confused about how the work-energy theorem for a single particle can be extended into the general law of conservation of energy for the macroscopic system, particularly the point where we divide the kinetic energy of the system into macroscopic kinetic energy and internal kinetic...

Homework Statement Exam review question concerning 2 dimensional motion, the professor did not hand out an answer key and I am just looking for an answer check. A car launches at an angle of 30 degrees above the horizontal, off a cliff (50m), moving at an initial speed of 10m/s. Find the...

I have a question about conservation of energy in my system A heat pump allows you to move a quantity of heat with a smaller energy input. It is most efficient for small temperature differences. A heat engine allows you to convert a temperature difference into mechanical work. It is most...

(This though came up while learning about band structure, so that is how I am going to explain it, but I think it applies equally well to a square well, for example). Say you have an electron at the Fermi level of an insulator. Then, you apply an electric field. No current flows, because all...

this would be considered as an inelastic collision where (m1v1) + (m2v2) = (m1+m2)vf also the conservation of energy being (∆K +∆U)=0 i tried using the conservation of energy to find v2 as the variable we are looking for is Vf, the speed the bullet leaves the block, and v2 (velocity of the...

Homework Statement A uniform ladder having mass 14kg and length 3m is released from rest when it is in the vertical position. If it is allowed to fall freely, determine the angle Theta at which the bottom end A starts to lift off the ground. For calculation assume the ladder is a slender rod...

Homework Statement A load of 10 kg is pulled up a lubricated slideway, set at an angle of 30° to the horizontal, such that the load is accelerated from rest to a velocity of 1 m/s whilst traveling up the plane through a distance of 1 m. The frictional resistance to this motion is 10 N and g =...

Homework Statement :[/B] There is a system, beginning from rest, with two masses, m1 and m2. M1 is on a table and attached to a rope that goes over a pulley (that is NOT massless)and attaches to hanging mass m1. Between m2 and the table there is a friction(kinetic) of 0.1 M1=10kg M2=30kg Mass of...

Where, when, and why did the notion of conservation of energy become a law? I know that we are able to "invent" new means of "fixing" any apparent violations of this and further I understand that the new inventions of other energy forces have led us to new ways of seeing the world but I still...

Homework Statement It's a simple problem, you kick a ball with an initial velocity of 5.4 m/s, the angle is 30 degrees. So the question is when does it land on the ground? So I thought that I could find final velocity so that I can use V = V(initial) + acceleration * time. My question is, can...

Homework Statement If you dive into water, you reach greater depths than if you do a belly flop. Explain this difference in depth using the concept of conservation of energy. Explain this difference in depth using what you have learned in this chapter**. ** It is referring to the chapter of...

Homework Statement [/B] A wheel rolls without slipping on a plane, what magnitudes are conserved? The Attempt at a Solution . [/B] I don't know if the static friction force does any work. Energy won't be conserved if it does.

Homework Statement A 900-kg car initially at rest rolls 50m down a hill inclined at an angle of 5.0^o. A 400-N effective friction force opposes its motion. (a) How fast is the car moving at the bottom? (b) What distance will it travel on a similar horizontal surface at the bottom of the hill...

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

Homework Statement The potential energy for a mss m = 1.0 kg moving in one dimension is given by U(x) = (2.5J) sin πx. The mass starts at x = 0 with an initial velocity v = 0.71m/s. (The plus sign means the motion is in the positive x-direction.) Describe the subsequent motion of the mass...

Homework Statement A bullet has a mass of 7.5 g. It is fired into a ballistic pendulum. The pendulum's receiving block of wood is 2.5 kg. After the collision, the pendulum swings to a height of 0.1 m. What is the approximate velocity of the bullet? m_{bullet} = 7.5g = 0.0075 kg m_{wood} = 2.5...

So negatives always get me, no matter what and I'm having a hard time understanding the conservation of energy. Anywho, I'll continue. In a system, oh let's say a block on a rough surface with some intitial v and kinetic energy K at point A. After it gets to B, friction has done W amount of work...

Homework Statement An assembled system consists of cart A of inertia mA, cart B of inertia mB, and a spring of negligible inertia, clamped together so that the fully compressed spring is aligned between the front end of cart B and the back end of cart A. The internal energy of the system...

Homework Statement A 710kg car drives at a constant speed of 23m/s . It is subject to a drag force of 500 N. What power is required from the car's engine to drive the car (a) on level ground? (b) up a hill with a slope of 2.0o? Express your answer to two significant figures. Homework Equations...

Hi, Consider a person who holds a light source of frequency f. Consider an observer who sees this light. The energy of each photon as received by the observer is E = hf. The observer is now fixed. Now suppose that the person who holds the light source starts to move towards the observer, then...

If I understand the basics correctly, the idea behind the Large Hadron Collider is to discover de Higgs boson. To do this, they accelerate protons to 99,99999% the speed of light. I think it was Einstein who said that no particle with mass can ever reach the speed of light, there is a physical...

Homework Statement A mass starts from rest and slides a distance d down a frictionless θ deg incline. While sliding, it comes into contact with an unstressed spring of negligible mass, as shown in the figure below. The mass slides an additional distance as it is brought momentarily to rest by...

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...

This problem was given verbally during a class period, so I will set it up in my own words. A bullet (.012kg) is fired at a block (.800kg) hanging on a strong, massless string of length 1.6m. After the collision the bullet is embedded in the block. When the block is .8m above its original...

Hi everyone, I've been working on this problem for a while now, and I was hoping someone here could point me in the right direction. Here goes: 1. Homework Statement A solid brass ball of mass 0.280 g will roll smoothly along a loop-the-loop track when released from rest along the straight...

Homework Statement PLEASE HELP: A bead at the end of a vertical spring moves without friction along a horizontal wire. WHen the spring is perfectly vertical , the spring is neither stretched or compressed. Show that the bead experiences a restoring force, and that if x is small, then the...

Homework Statement During a rockslide, a 710 kg rock slides from rest down a hillside that is 500 m long and 300 m high. The coefficient of kinetic friction between the rock and the hill surface is 0.23...

Homework Statement Gayle runs at a speed of 4.20m/s and dives on a sled, which is initially at rest on the top of a frictionless snow-covered hill. After she has descended a vertical distance of 4.77m, her brother, who is initially at rest, hops on her back and together they continue down the...

Homework Statement Suppose that a certain accelerator can give protons a kinetic energy of 200 GeV. The rest mass of a proton is 0.938 Gev/c^2. Calculate the largest possible rest mass M0 of a particle that could be produced by the impact of one of the high-energy protons on a stationary...

::A skier of mass 63.0kg starts from rest at the top of a ski slope of height 62.0m .A skier of mass 63.0kg starts from rest at the top of a ski slope of height 62.0m .A) If frictional forces do −1.00×104J of work on her as she descends, how fast is she going at the bottom of the slope? Take...

EDIT: Hey I'm Honey. I'm a college level introductory physics student.

Homework Statement Homework Equations ## W_{nc} = \Delta KE + \Delta PE ## ## PE = mgh ## ## KE = \frac{1}{2} mv^2 ## The Attempt at a Solution For Block B, ## \Delta KE + \Delta PE = \frac{1}{2} 100 v^2 + (-20)(g)(100) ## For Block A, ## \Delta KE + \Delta PE = \frac{1}{2} 50 v^2 + (20...

Homework Statement A ball of mass 1 Kg is dropped from a height of 7m and rebounds to a height of 4.5m Calculate: its kinetic energy just before impact the initial rebound velocity of the ball and kinetic energy. Account for loss of kinetic energy on impact...

Hi all, I'm not 100% sure this belongs in this topic but it was a problem I was given in a quantum mechanics lecture so here goes, sorry if I am wrong.Anyway I was given a hamiltonian H= T+VWhere T is kinetic energy and av is potential, and asked to use dH/dt= 0 to find an analogy between...

Hello, Suppose that an object of rest mass m0 travels to the right with speed v1. A photon of frequency f also travels to the right and hits the object. The photon is fully absorbed by the object and then the object travels to the right with the (unknown) speed v2 after collision. Now, the...

Homework Statement A child slides without friction from a height h along a curved water slide (Fig. P5.44). She is launched from a height h/5 into the pool. Determine her maximum airborne height y in terms of h and η. (Use q for η and h as appropriate.) (Fig. P5. 44) Homework Equations I know...

Homework Statement The force on a particle, acting along the x axis, varies as shown in the figure below. (a) Determine the work done by this force to move along the x-axis from x=0.0 to x = 10.0m and (b) from x=0.0 to x=15.0m and (c) what is the speed of the particle at each slope change and...

Homework Statement (apologies for the bad picture, but it was the only one I could find online) Homework Equations Conservation of energy, KE1 + PE1 = KE2 + PE2 PE = mgh KE = 0.5mv² The Attempt at a Solution I'm not sure where to begin. I know the answer but I don't know how you get it...

Life started from a single cell, right? And now we have countless number of cells on our planet. So is this like new matter being created? So there is more energy on the planet as of now? How is the energy on the planet being conserved? I possibly framed the question wrong, but I hope you...

Homework Statement A billiard ball of mass M is initially at rest on a horizontal frictionless table. Another ball of mass m < M and velocity ##\vec{v}## in the positive x-direction hits the first ball in a pefectly elastic collision. After the collision, the balls move with (unknown)...

Homework Statement A billiard ball of mass M is initially at rest on a horizontal frictionless table. Another ball of mass m < M and velocity ##\vec{v}## the positive x-direction hits the first ball in a perfectly elastic collision. After the collision, the balls move with (unknown) velocities...

1. A 1 kg block is on a flat frictionless surface. Attached to a relaxed spring (k=50N/m). A light string is attached to the block and runs over a frictionleas pulley to a .45kg dangling mass. If the dangling mass is released from rest, how far will if fall before stopping? Homework Equations...

Homework Statement Two spheres are hanging from cords as shown. The distance from the ceiling to the center of each sphere is 2m, and the coefficient of restitution is 0.75. If sphere "A" (m_a = 2kg) is drawn back 60^o and released from rest, determine: a) The maximum angle, θ_B , that sphere...

This isn't homework. I'm reviewing physics after many years of neglect. Since a simple harmonic oscillator is a conservative system with no energy losses, then a driven undamped harmonic oscillator, once the transient solution has died out, can't be receiving any energy from the driving...