Conservation of energy Definition and 1000 Threads

Homework Statement Two small metal spheres with masses 2.0g and 4.0g are tied together by a 5.4-cm-long massless string and are at rest on a frictionless surface. Each is charged to +2.1 μC . The string is cut. What is the speed of each sphere when they are far apart? Homework Equations...

Write the conservation of energy equation for this situation and solve it for the speed of the mass as it passes equilibrium. A horizontal spring attached to a wall has a force constant of 900 N/m. A block of mass 1.20 kg is attached to the spring and oscillates freely on a horizontal...

Homework Statement You have a pair of inclined planes such that a block that slides down one can slide up the other without losing any energy in the transition. The inclined planes are both at an angle θ from the horizontal, as shown in the diagram. The inclined plane on the left is...

Homework Statement A boy at the top of a roller coaster falls through a vertical distance of 20m. What is the final speed of the boy if: a) His initial speed was 0 b) His initial speed was 5 ms-1 Homework Equations GPE at top = KE at bottom mgh = 1/2mv^2 gh = 1/2v^2 v = √2gh if...

Homework Statement When a tether ball wraps around a pole, the speed of the ball does not change. I need to explain why using conservation of energy but am struggling in this class and need to see if I'm on the right track. The second part of the problem states that if the length of the tether...

Homework Statement This probably seems really obvious but what formula do you use to find velocity with conservation of energy? Once you find the velocity, is it the velocity of the object at the bottom of the height? Homework Equations This is what I'm not sure about. Is it mgh=0.5mv^2?

Homework Statement A closed system initially at rest on the surface of the Earth undergoes a process for which there is a net energy transfer to the system by work of 200 Btu. During the process, there is a net heat transfer from the system of 30 Btu. At the end of the process, the system has...

Homework Statement A) How much work would it take to push two protons very slowly from a separation of 2.00*10-10 m (a typical atomic distance) to 3.00*10-15 m (a typical nuclear distance)? B) If the protons are both released from rest at the closer distance in part A, how fast are they...

A pendulum is suspended from the ceiling and attached to a spring fixed to the floor directly below the pendulum support. The mass of the pendulum bob is m, the length of the pendulum is L, and the force constant is k. The unstressed length of the spring is L/2 and the distance between the...

Hi, I've been reading chapter 4 in the Feynman Lectures on the conservation of energy and I've bought a book off amazon called Exercises in Introductory Physics which accompanies the series. Having looked at some of the questions I feel well out of my depth because essentially I haven't ever...

Greetings all, I'm new here. I've looked through some of the topics on virtual particles and I'm still a little confused. In Philosophy, you don't get something from nothing. In physics, there's no such thing as a free lunch. Yet many on web pages about physics a claim is being made that...

If the acceleration of the expansion of the universe is driven by the vacuum energy 'created' by newly-formed space, what is the counterpart of this energy? Is it a net surplus energy injected into the universe and not converted from another pre-existing form of energy? In that case, is the...

A pendulum consists of a 2.0-kg bob attached to a light 3.0-m-long string. While hanging at rest with the string vertical, the bob is struck a sharp horizontal blow, giving it a horizontal velocity of 4.5 m/s. At the instant the string makes an angle of 30° with the vertical, what is (a) the...

Homework Statement Consider a mechanical system describe by the conservative 2nd-order ODE \frac{\partial^{2}x}{\partial t^{2}}=f(x) (which could be non linear). If the potential energy is V(x)=-\int^{x}_{0} f(\xi) d \xi, show that the system satisfies conservation of energy...

Homework Statement A stone is thrown upward at an angle of 53° above the horizontal. Its maximum height above the release point is 24 m. What was the stone’s initial speed? Assume any effects of air resistance are negligible. Homework Equations Emech=0 The Attempt at a Solution On...

Is conservation of energy, momentum, and other physical properties absolutely true in quantum mechanics, or only on average? As an example, think of a single particle in free space. Measure its energy, and write down the result. Then look at where it is, and measure the energy again. You'll...

Homework Statement Conservation of energy You are designing a game for small children and want to see if the ball’s maximum speed is sufficient to require the use of goggles. In your game, a 15.0-g ball is to be shot from a spring gun whose spring has a force constant of 600 N/m. The...

When an em-wave red shifts due to leaving a gravitational field it loses energy, right? Where does that energy go, into gravitational potential energy of the photon? If so does this mean that the photon can "fall" back on the gravitating body to reclaim this energy? What happens to the energy if...

I won't pretend to by a physicist (yet... maybe in four years :frown:) but I do surf Wikipedia a lot now and then. So I came to a general understanding (I think?) of how transportation through wormholes has you arrive at a frame in the past. Wouldn't this violate the conservation of energy...

Homework Statement Motorcycle in a vertical loop. Traveling at 50 m/s. Assume g=10 m/s^2 Find the maximum height of the loop. h=? Homework Equations F(net) = F(cent) + F(grav) F(cent) = mv^2/r F(grav) = mg (change) KE = (change) PE KE = 1/2 mv^2 PE = mgh The Attempt at a Solution F(net)...

Hi, I'm doing a project on the Gauss gun and Newton's cradle. I'm trying to produce little models in MatLab and have come across some problems. Namely with the gauss gun, using different types of balls, hollow and solid (I've not even got round to adding acceleration from a magnet yet)...

Homework Statement Question: An airplane is 250m from the zero heigh and drops a package: a. What is the objects kinetic energy if the velocity is moving at 10m/s. How much energy is left? What height should the object be at? b. What is the objects kinetic energy if the velocity is...

If all frames of reference are taken as equally valid. when a car moves, to the passengers in the car the world is moving in the opposite direction. Moving the whole world should take a lot more chemical energy than was contained in the gas that was burnt... I know the passengers in the car...

A block starts at rest and slides down a frictionless track except for a small rough area on a horizontal section of the track (as shown in the figure attached for#007). It leaves the track horizontally, flies through the air, and subsequently strikes the ground. The acceleration of gravity is...

I have two springs. I compress one (it stays compressed) and throw it in acid and measure the energy that comes off, I do the same for the other spring but leave it uncompressed. Which gives off more energy and why? The answer is obvious but I don't see how the acid eating the springs would...

Homework Statement Homework Equations The Attempt at a Solution I do not understand how in the solution they come up with the first equation that I boxed in with green. I know that the total energy before is equal to the total energy after but I don't understand the logic of how they formed...

Energy and momentum only differ by a factor of V/2. So in essence, at a fundamental level, does this mean that the conservation of energy is the conservation of momentum in disguise? IH

Would I be right in saying the following: Potential energy arises from the conservation of energy. To lift a mass you must exert a force counteracting the force of gravity. As it moved and a force was exerted work was done on it. As it is not moving it has no kinetic energy. Due to the...

Gday, This may be a trivial questiom, but I just cannot figure it out. Why is mechanical energy conserved with an elliptical orbit? I understand that the mechanical energy of the system, i.e. both bodies, is conserved, but how is this isolated to the satellite's mechanical energy being...

Homework Statement A 0.50 kg ball accelerated from rest by a 8.0 N force for 3.0 m Homework Equations W=E Ek= 1/2mv2 Ep=mgh The Attempt at a Solution Given: mass= 0.50 Kg, V=0m/s, F=8.0 N, d=3.0 m Ek=1/2mv2 =1/2(0.50 kg)(0 m/s)2 =o J That's wrong

[b]1.Ball 1 with an initial speed of 14 m/s has a perfectly elastic collision with Ball 2 that is initially at rest. Afterward, the speed of Ball 2 is 21 m/s. What will be the speed of Ball 2 if the mass of Ball 1 is doubled. [b]2. conservation of momentum: m1(v1i)=m1(v1f)+m2(v2f)...

Homework Statement http://www.austincc.edu/mmcgraw/Labs_1401/8c-Con%20of%20Energy-Pendulum-RGC-1-15-09.pdf state some errors that occurred in the lab Homework Equations The Attempt at a Solution I think it has something to do with the photogate but I am not sure.

Homework Statement A marble of mass M and radius R rolls without slipping down the track on the left from a height h1, as shown below. The marble then goes up the frictionless track on the right to a height h2. Find h2. (Use the following as necessary: M, R, and h1.) http://imgur.com/sZIyQ...

If a body moves along a quarter of a circle and it is subject only to conservative forces, it is relatively easy to deduce the equation of motion. But if friction comes into action, it seems more difficult. Suppose that a body has initial velocity v_0 and that it moves along a quarter of a...

Homework Statement A pen of mass 0.057 kg slides across a horizontal desk. In sliding 25 cm, its speed decreases to 5.7 cm/s. The force of kinetic friction exerted on the pen by the desk has a magnitude of 0.15N. Apply the law of conservation of energy to determine the initial speed of the...

Homework Statement A rotating uniform cylindrical platform that forms the base of carnival ride has a mass of 248 kg and radius of 4.8 m. The platform slows down from 4.6 rev/s to rest in 14.9 s when the motor is disconnected. Determine the power output required to maintain a steady...

Okay, my title may have been a bit overdramatic ... but my question is still about something a bit troubling I read in Sean Carroll's GR text. Basically, he claims that the total energy in an expanding Universe is not typically conserved. See pages 137-138 and 344. This is because...

If due to redshift, light shifts towards the red end of the spectrum and the energy of photons = hc/\lambda, then how does this reduction in energy of the photons not violate the conservation of energy law?

I know that the law of conservation of energy is not violated by either complete destructive interference or capillary action, but I'm curious then what happens to the energy and where it comes from in these cases, since I can't figure it out. Consider the case of complete destructive...

Homework Statement A mass M is in static equilibrium on a massless vertical spring as shown in the figure. A ball of mass m dropped from certain height sticks to the mass M after colliding with it. The oscillations they perform reach to height 'a' above the original level of scales & depth...

The two masses in the Atwood's machine shown in Figure 8-23 areinitially at rest at the same height. After they are released, thelarge mass, m2, falls through a heighth and hits the floor, and the small mass,m1, rises through a height h. (a) Find the speed of the masses just beforem2 lands...

Homework Statement A uniform solid sphere rolls on a horizontal surface at 20m.s^-1 and then rolls up an incline which has an angle on inclination of 30°. Ignoring friction, calculate the height attained by the sphere. Homework Equations Weren't given any specific equations to work...

Homework Statement 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 cannon mounted on a table. The target box is 2.2m horizontally away from the edge of the table. The spring is compressed 1.1cm, but the ball falls...

Hello everyone, I'm not sure that this fits in the general physics topic but here it is anyway: If you have a certain mass on a planet that you convert to energy, specifically photons (just because it seems to make sense to me) and 'send' those photons to another planet where they will be...

Homework Statement A 194 block is launched by compressing a spring of constant 200 N/m distance of 15cm . The spring is mounted horizontally, and the surface directly under it is frictionless. But beyond the equilibrium position of the spring end, the surface has coefficient of friction 0.27...

Homework Statement Suppose you left a 100w light bulb on continuously for one month. If the electricity generation and transmission efficiency is 30%, how much chemical energy (in joules) was wasted at the power plant for this oversight? if the fuel consumption for one meal in China using...

Homework Statement A pendulum swings from a height and its string hits a nail as shown in the diagram. At which position A, B, or C will the bob end? Homework Equations The Attempt at a Solution I think that the answer is B cos of law of conservation of energy. Is this the...

Homework Statement A 2.10 multiplied by 103 kg car starts from rest at the top of a 4.7 m long driveway that is sloped at 20° with the horizontal. If an average friction force of 4.0 multiplied by 103 N impedes the motion, find the speed of the car at the bottom of the driveway. Homework...

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...