Conservation of energy Definition and 1000 Threads

Greetings, When a photon travels through expanding space, it's frequency decreases and it has less energy. The energy of photons of the cosmic background radiation have decreased dramatically. Where does the energy go? Is it lost? Thanks

Spring compression -- Conservation of Energy Homework Statement So far I'm only working on part A. I didn't know whether to create separate posts for each part I had trouble with or just put the whole thing in one post. Homework Equations KE = 1/2mv^2 PE = mgh Uelas = 1/2kx^2The Attempt at a...

When a PN juction is in the open circuit condition, my textbooks says the following. "The voltage measured between the terminals is zero. That is the junction Voltage Vo does not appear across between the diode terminals.This is because of the contact voltages existing at the...

Conservation of Energy -- Bungee Jumping Homework Statement Unstretched length = 139 ft k = 39 lb/ft Weight of jumper = 122 lbs Homework Equations Assuming he hasn't hit the ground, how much has the bungee chord stretched when the professor is at the bottom of the jump? (ft) The...

Homework Statement A spring has an equilibrium length of 1m. The spring is compressed to a length of .5m and a mass of 2kg is placed at its free end on a frictionless slope which makes an angle of 41degree wrt the horizontal. The spring is then releases. a. If the mass is NOT attached to the...

Homework Statement We had an air track and let a cart of mass m travel downhill. The we calculated the velocity and firther the kinetic energy K and the gravitational energy U. We did this to show that the total energy in the system stays constant. Now I need to answer the question if I...

Homework Statement http://www-teach.phy.cam.ac.uk/dms/dms_getFile.php?node=5735 problem B8, the one with the with finding h>11(R-a)/4 Homework Equations (1/2)mv^2=mgh ac=(v^2/R) w=V/R (1/2)mv^2+(1/2)Iw^2 The Attempt at a Solution At the top of the circle, the velocity squared is GR. And...

Homework Statement A system has two blocks connected by frictionless pulleys. One block (m = 3kg) is above the other (m = 2kg) vertically, as the other is lowered by a weight. Initially, they are 5m apart, vertically. When the weight is removed, what is the speed of the blocks when they are at...

Homework Statement A pair of charged conducting plates produces a uniform field of 12,000 N/C directed to the right, between the plates. The separation of the plates is 40 mm. In the figure, an electron is projected from plate A, directly toward plate B, with an initial velocity of 2.0 x 10^7...

Hi folks, I am new to physics forums , an engineer by profession, I have newly developed some interest for pure physics, can someone please enlighten me on the violation of energy conservation by the time energy UP? The way I understand it the principle only puts a LOWER bound. Is...

Suppose you build a heat engine. On one side you have a hot body, on the other side you have a cold body. Between the 2 you have the heat engine but on a parallel path you have a simple heat conductor. What will happen is that some of the heat will travel through and power the heat engine...

Homework Statement (a) If R = 12 cm, M = 570 g, and m = 50 g in Figure 10-18 (below), find the speed of the block after it has descended 50 cm starting from rest. Solve the problem using energy conservation principles. M is the mass of the mounted uniform disk. A block with mass m hangs from...

When a basketball is dropped then bounces up it reaches 0 kinetic energy, but it doesn't reach original height it was dropped from. Why does this not violate the Law of Conservation of Energy?

This is a conceptual question I've been thinking about dealing with conservation of energy. For example, say you have two charged spheres, one positive and one negative. The positive one is glued in place while you kick the negative one away. How fast would you have to kick the negative one...

If black holes exist, they can't consume infinite amount of matter, so where does this energy go if it is not dissipated? Is it gamma ray bursts that dissipate this huge amount of energy? Or maybe a better question is, once a black hole is created, how long can it last? or do they last forever?

1. A skier is pushed from the top of a hill so that he starts moving down the hillside sloped at 27.6° to the horizontal with an initial speed of 0.434 m/s. After traveling 80.4 m, he reaches the bottom of the valley. Due to inertia, he then continues 70.4 m up another hillside sloped at 20.7°...

Is it just as fundamental as Newtons Law of Motion or it is deeper than that? I mean, is it like- No matter what invention and discoveries you come up in future, no matter which theories fail and which emerge, this Law of Conservation of Energy shall always stand above all.

Suppose two massive bodies are far enough apart that the expansion of space precisely counteracts their gravitational attraction. While in this configuration a tether is strung between them, tied off to body A and wound around a pulley on body B. One of the bodies is then nudged so that the...

Here's the question: Two children are playing a game in which they try to hit a small box on the floor with a marble fired from a spring-loaded gun that is mounted on a table. The target box is horizontal distance D = 2.20 m from the edge of the table. Bobby compresses the spring 1.1 cm, but...

Hello everyone I am stuck on this question, hopefully someone can help me out, here is the question: 2kg block is sitting on surface while 3kg block is hanging. So far this is what I am thinking, the 2 blocks acts as a system, initially the block is 1.5m high, so mgy gives me the...

Homework Statement This is the conservation of energy in the absence of external forces ΔKE + ΔPE + ΔTE + ΔU= 0 TE is friction, U is other internal energy, like the spring So expand and disregard U and TE for a moment ½m(v² - v₀²) + mg(h - h₀) = 0 Now comes the...

Homework Statement http://www.collegeboard.com/prod_downloads/ap/students/physics/ap04_frq_physics_cm.pdf Question 2 part c) "Calculate the rotational inertia of the pulley" Answer Key: http://www.collegeboard.com/prod_downloads/ap/students/physics/ap04_frq_physics_cm.pdf...

1. Two spheres having masses M and 2M and radii R and 3R, respectively, are simultaneously released from rest when the distance between their centers is 12R. Assume the two spheres interact only with each other and we wish to find the speeds with which they collide. Write an equation from one of...

Homework Statement http://www.screencast.com/users/trinhn812/folders/Jing/media/6596c399-feb6-49cf-82a7-d6d16c2a88e8 Question 17 Homework Equations So I solved this problem using kinematics and would like to learn how to solve it use conservation of energy. I can't seem to get the right...

Law of conservation of energy homework help! Homework Statement A skier goes down a slope and goes over a ramp. From a resting position which has a height of 16m, she leaves a ramp of 9m at an angle of 45 degrees and passes over a haystack forming a 30degree angle vertically. Supposing...

Homework Statement Got an assignment from the teacher to present a problem I have made by myself and show how I have done it, so I have no answer to refer to in this particular question. Anyways, A car is pushed so that it gains a speed of 2m/s just off a steep road, which has an angle of 35...

Homework Statement Jonathan is riding a bicycle and encounters a hill of height h. At the base of the hill, he is traveling at a speed vi. When he reaches the top of the hill, he is traveling at a speed vf. Jonathan and his bicycle together have a mass m. Ignore friction in the bicycle...

I have three questions here, and I am a bit confused about what "relative to" means in this context: 1."A 1.91 kg ball is attached to a ceiling by a 3.28 m long string. The height of the room is 5.94 m . The acceleration of gravity is 9.8 m/s2 . What is the gravitational potential energy...

Conservation of Energy and Momentum "Lie" Homework Statement Each marble on a Newtonian demonstrator has a mass m, and the 1st marble hits the others with a velocity v. 1. Using the law of conservation of momentum - determine the velocities for: a. Two marbles moving up b. Three...

Homework Statement Two objects are connected by a light string passing over a light frictionless pulley as shown in the figure. the 5.87 kg object is released from rest at a point 2.55m above the floor. The acceleration of gravity is 9.8 m/s^2. What is the speed of each object at the instant...

Homework Statement A solid, uniform spherical ball rolls without slipping up a hill. At the top of the hill it is moving horizontally, and then it goes over a vertical cliff. How far from the foot of the cliff does the ball land, and how fast is it moving before it lands. Use conservation...

Homework Statement A projectile is shot directly away from Earth's surface. Neglect the rotation of Earth. What multiple of Earth's radius R_e gives the radial distance a projectile reaches if its (a) initial speed is .5 the escape speed from earth, (b) its initial kinetic energy is .5 of the...

Homework Statement A 2.7 kg bundle starts up a 27° incline with 106 J of kinetic energy. How far will it slide up the incline if the coefficient of kinetic friction between bundle and incline is 0.42? Homework Equations K= 1/2mv^2 conservation of energy => Ki + Ui = Kf+Uf The...

Homework Statement A .4 kg ball is thrown with a speed of 12 m/s at an angle of 33 degrees. What is its speed at its highest point, and how high does it go? Use conservation of energy and ignore air resistance. Homework Equations mgyi+1/2mvi2=mgyf+1/2mvf2 The Attempt at a Solution...

A 2.0 kg ball at rest is struck head-on by a 5.0 kg ball moving along a track at 10.0 m/s in an elastic collision. What is the speed of the 5.0 kg ball and the 2.0 kg ball after the elastic collision? ----I'm sure this is a pretty simple question but I don't where to start. Is the following...

Homework Statement An 8 g bullet is fired into a 2.5 kg block initially at rest at the edge of a frictionless table of height 1 m. The bullet remains in the block and lands 2 m from the bottom of the table after impact. Determine the initial speed of the bullet. Answer: 1392 m/s...

Homework Statement A 15 kg child slides, from rest, down a playground slide tht is 4.0 m long, as shown in the figure. The slide makes a 40 degrees angle with the horizontal. The child's speed at the bottom is 3.2 m/s. What was teh force of friction that the sldie was exerting on the child...

Homework Statement From what height would a compact car have to be dropped to have the same kinetic energy that it has when being driven at 105 km/h? Unless otherwise directed, assume that air resistance is negligible. Answer: __ m Velocity: 105 km/h -> 105000 m/s Height: ...

A physics book of unknown mass is dropped 4.20 m. What speed does the book have just before it hits the ground? Unless otherwise directed, assume that air resistance is negligible. Height: 4.20 Acceleration: 9.81 Mass: ? Velocity: ? The answer box is for velocity: ___ m/s Homework...

A 1.6 kg breadbox on a frictionless incline of angle θ = 36° is connected, by a cord that runs over a pulley, to a light spring of spring constant k = 120 N/m, as shown in the figure below. The box is released from rest when the spring is unstrectched. Assume that the pulley is massless and...

Car has a mass of 1000 kg its at a the top of a 10 degree hill. so if you were to draw a triangle the the base of the triangle would be 50 M in length as well. a)what is it gravitational potential energy relative to the bottom of the hill? Height = 50 * Tan 10 = 8.816 Potential...

Homework Statement Exactly one turn of a flexible rope with mass m is wrapped around a uniform cylinder with mass M and radius R. The cylinder rotates without friction about a horizontal axle along the cylinder axis. One end of the rope is attached to the cylinder. The cylinder starts with...

I am having trouble with the following problem: With what velocity should a projectile be started ar the center of the Earth to reach the surface of the Earth? When I attempt to solve this using 1/2mv^2 = -(GMm)/R I get an answer of 11.8 km/s. However, the correct answer is 7.9km/s. I...

Homework Statement Bungie Jumper starts 65 meters from ground. Wants to end fall 10m from ground (55 meters from the top). Cord follows Hookes law. We know that when his body weight hangs at rest from a 5 meter section of cord, he stretches the cord 1.5 meters. How long should his cord be...

Homework Statement see the diagram two posts below this. A bead slides on a wire, which is in a vertical plane, as shown in the diagram. Gravity acts in the -y direction. The bead starts at A, moving to the right with an initial velocity v. The wire is frictionless between A and D and between F...

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 speed vf. Ignore air resistance, and assume that any changes in kinetic energy of the Earth are negligible. Also, the starting velocity of the ball is zero...

What should a graph of potential energy versus kinetic energy look like. My graph is linear but I'm pretty sure it should look like a parabola.

What should a graph of potential energy versus kinetic energy look like. My graph is linear but I'm pretty sure it should look like a parabola.

Homework Statement A mass starts at top of incline with a length of 10 meters with an angle of 36 degrees. Incline has friction with a coefficient of kinetic friction of .26. At bottom of incline is a horizontal, frictionless surface which has a loop of radius 2 meters. After loop is a...

Homework Statement A massless spring has unstretched length Lo = 0.45 m and spring constant k = 122.3 N/m. A block of mass m = 1.87 kg is attached to the spring, and a student stretches the spring to a length of L = 1.1 m. Then the student releases the block and it shoots upward. What is...