Conservation of energy Definition and 1000 Threads

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...

Homework Statement I get that less percentage energy is conserved from potential to kinetic energy by measuring h and v with two balls for the heavier ball. I am trying to sort of why actually is like that! Two balls where dropped down from a ramp with different masses and volume. The smaller...

Homework Statement A photon with energy E collides with stationary mass m. They form a single particle together, what is this new particle's mass and what is its speed? Homework Equations Energy-momentum 4-vector P=(E, px, py, pz) Possibly P2=m2 The Attempt at a Solution Using 4- momenta, the...

Having problems with part (c) here, question is attached below in full. Homework Statement Using the equation 1/2 * Load * Displacement = Sum of (P^2 * L/2AE) From the past questions I have the following info, these are also included in the solutions so are accurate: A = 1x10^3 m^2 FAB =...

I was reading through some main stream scientific literature, and I came across Sean Caroll's "Energy Is Not Conserved" post. Essentially, he contends that through general relativity energy is not conserved, at least not in conventional manner of thinking about energy. Anyways, some portions of...

This had me thinking for a while. Imagine a photon emitted by a very distant object at a redshift of z = 2.0 for example. As the photon travels through space, due to space expansion the photon's wavelength will shift towards red. With an increase in the wavelength there must come a decrease in...

Well this question has been in the mind since a long time. I believe that the law of conservation of energy is not true. If it is/was true then why would the universe expand and into what is it expanding ? obviously energy is created when the universe expands into "NOTHING". I will be waiting...

Homework Statement [/B] A block of mass m is attached to a spring with a force constant k, as in the above diagram. Initially, the spring is compressed a distancex from the equilibrium and the block is held at rest. Another block, of mass 2m, is placed a distance x/2 from the equilibrium as...

I find this problem kind of tricky. I think it must be a, since a change in momentum of the car causes the same change in momentum of the earth.

Let's say a tennis ball with velocity with only an horizontal component hits a vertical wall at rest. After collision, conservation of momentum tells that : m_{wall}v_{wall} = 2m_{ball}v_{ball} Thus, the wall has now a (tiny) velocity and kinetic energy : v_{wall} =...

Homework Statement Two masses are connected by a light string passing over a light, frictionless pulley, as shown in the figure below. The mass m1 (which is greater than m2) is released from rest. Use the isolated system model to answer the following. In terms of m1, m2, and h, determine the...

Homework Statement We are trying to find out whether we can hit a weight ##m=3## kg up to a given ##h=15.24## meters with a hammer with a head of ##m=6## kg swung at ##v=10## m/s. Homework Equations KE=0.5mv^2 PE=mgh p=mv The Attempt at a Solution One solution is to even see if the energy...

I'm wondering about how one would describe the dynamics of a rotating sphere. Consider this: a solid sphere of mass "m" and radius "r" is set to rotate about a tangent to its surface. If it is released from the horizontal position such that it swings like a pendulum, what would be the force...

Homework Statement The statement of the question is:A chain of uniform linear mass density ##\rho##, length ##b## and mass ##M## hands as shown in the figure below. At time t=0, the ends A and B are adjacent, but end B is released. Find the tension in the chain at point A after end B has...

Homework Statement m(person) = 60kg v1 = 3.0m/s v2 = 0 d = 2m y1 = -1m y2 = 0 A person is completing a long jump. At event 1 they are 1m in the air and are moving at a rate of 3.0m/s. At event 2 they are at rest on the ground, 2m from their initial landing place. What is the stopping force...

A 1.2 kg cart slides eastward down a frictionless ramp from a height of 1.8 m and then onto a horizontal surface where it has a head-on elastic collision with a stationary 2.0 kg cart cushioned by an ideal Hooke’s law spring. The maximum compression of the spring during the collision is 2.0 cm...

Homework Statement I'm trying to confirm the speed of an antimuon in the \pi^+ \rightarrow \mu^+ \nu_{\mu} decay through the laws of conservation but it doesn't add up. Homework Equations [/B] 1.Energy-momentum relation: E^2 = (pc)^2 + (mc^2)^2 2. Rest masses: m_{\pi} = 139.6 \...

Hi, Consider the conservation laws for an isothermal linear incompressible flow governed by the mass and momentum equation. The kinetic energy equation is then solved to see if energy conserved. Can anyone tell me if once it is shown energy is conserved, it implies that convergence is obtained...

Using a more physics oriented approach, rather than a chemistry one, and looking to an energy point of view if possible. For example, why when ice turns into water there is a need for energy (heat)? I know in some extent that the energy is used into re-organizing the chemical bonds, but that...

Homework Statement A 700g block is released from rest at height Ho(initial) above a vertical spring with spring constant k=400 N/m and negligible mass. The block sticks to the spring and momentarily stops after compressing the spring 19.0 cm. How much work is done A) by the block on the spring...

1. A ball falls to the ground through the air. Is the energy of the air conserved?2. None3. When a ball falls to the ground a transformation of energy occurs. The previously stored potential energy gradually becomes kinetic energy during its fall. The energy conserved in the air is the slight...

The conservation of the energy of the universe requires that the universe is an isolated system. Is there any way that, in fact, the universe isn't a isolated system and we would be losing or gaining energy in the universe? Also, does this possibly mean that the universe won't necessarily end in...

I am a big physics enthusiast, and I apply my learning as much as possible. Today, my literature teacher introduced this idea that when coffee and sugar are combined, new calories are born. For instance, coffee (0 kcal) + sugar (100 kcal) = 150 kcal? Unfortunately, I only pursued physics and...

Does the law of conservation of energy make valid predictions when energy is converted from gravitational potential energy into kinetic energy?

Homework Statement Problem statement and diagram in the photo Homework Equations K = 1/2 mv^2 U = mgh The Attempt at a Solution E_0 = E1 K_0 + U_0 = K_1 + U_1 using relevant equations and solving for v1 I get: v_1 = sqrt((v_0)^2 + 2gh_1) Then E_1 = E_2 solving for the final velocity and...

Homework Statement A spring (k = 2900 N/m ) is compressed between two blocks: block 1 of inertia 1.70 kg and block 2 of inertia 2.00 kg. The combination is held together by a string (not shown in (Figure 1) ). The combination slides without spinning across low-friction ice at 2.90 m/s when...

When a galvanic reaction reclaims its (single) electron, magnetic energy (about 0.356 eV) within a superconductor will remain, w/o a means of replacing the galvanic electron. During the reaction, electrical current from the single electron would correspond to the number of times per second...

Homework Statement A man on his bike have an initial velocity of 8.5m/s. He begins to go up an incline that has a vertical height of 5.2m. Once he reaches the top of the incline, he only has a velocity of 3.00m/s. The man and his bike combined weigh 80kg. What is the total work done on the...

Homework Statement An amount of work equal to 1.5 J is required to compress the spring in a spring gun. ? Homework Equations Wtotal = change of KE[/B] The Attempt at a Solution W=ΔKE=(1/2)m(Vf² - Vi²) It sounds like the Vf >0 and would be maximum after the spring is compressed hard and...

A 2.00-kg ball has zero kinetic and potential energy. John drops the ball into a 10.0-m-deep well. 1) Just before the ball hits the bottom, the sum of its kinetic and potential energy is: Zero J 2) After the ball comes to a stop in the mud, the sum of its potential and kinetic energy is: -196...

A simple pendulum, 2.0 m in length, is released by a push when the support string is at an angle of 25° from the vertical. If the initial speed of the suspended mass is 1.2 m/s when at the release point, to what maximum angle will it move in the second half of its swing? Let h1 be the...

Homework Statement A daring friend of yours talks you into bungee jumping from the Royal Gorge Bridge, in Colorado. Starting from the bridge (at rest), you launch off and fall first to the unstretched length of the bungee, 153 m. The bungee then stretches until you reach the full drop distance...

Are there situations when conservation of Energy does NOT apply? Thanks.

Homework Statement Homework EquationsThe Attempt at a Solution 4a at x=-2 F=0N Potential energy=integration of F(-2)=Integration of 0=0 so it will reach minimum at x=-2? b. integration of F(-2)-integration of F(-2-h)=m(v-0)^2/2 am i right? 5 Centripetal force=mv^2/r=mgsinθ-Fn(normal force)...

Homework Statement Homework EquationsThe Attempt at a Solution I know that the velocity of mass at the bottom of the swing is V = Sqrt(2gh), but I'm not sure how to get from there to the velocity of A. Is it as simple as Angular momentum of B = Linear Momentum of B?

Hello! I'm new to this forum but ok let's get this started, First I'll revisit the definition I know as physics; the study of nature in order to provide a reasonable(radical/rudimentary) explanation/reason. This I believe in is not quite how things are today, at school, with my teachers or at...

Homework Statement A block of mass ##m## slides down a wedge of mass ##M## and inclination ##\theta## whose surfaces are all frictionless. Find the velocity of the block when it just reaches the bottom of the wedge. Homework EquationsThe Attempt at a Solution I was told that to solve this...

Homework Statement "identify the type of energy conversions present in each of the following situations. Some questions may use multiple types of energy." 1) a wind turbine producing electricity 2) two children sliding down a hill on a toboggan 3) a toaster oven browning a bagel Homework...

As another of my personal music projects, I have wondered if it would not be possible to calculate the 'feel' of a drumhead (i.e. the amount of 'give' expressed as transverse displacement 'z' that an equally pre-tensioned circular membrane of radius 'r' experiences when struck on its plane at a...

Hi guys! one quick question, if in a quantum system the hamiltonian of a particle evolves with time (let's say, the potential is a function of t), the energy is not conserved right? I just want to be sure about this, thanks!

So, this seemed really fun to me until I got stuck. THE TASK is about an object with mass m, moving in a basic (2D) coordinate system. It is attached to origo (0, 0) by a "rope" with constant length r=5. In position P0(-5, 0) it has the velocity v0=[0, -10]. Hence, the object moves around origo...

Homework Statement Find the minimum force ##\displaystyle F## required to move ##\displaystyle M_2##.Details and Assumptions: ##\displaystyle M_1 = 3Kg## ##\displaystyle M_2 = 5Kg## ##\displaystyle \mu_1 = 0.4## ##\displaystyle \mu_2 = 0.6## ##\displaystyle g = 9.8m/s^2## Homework...

Hi, Some "derivations" of the law of the lever argue with conservation of energy: If one arm of the lever of length ##r_1## is pulled by a distance ##s_1## with force ##F_1##, the other arm moves by a distance ##s_2=s_1 \frac{r_2}{r_1}##. From conservation of energy ##E=F_1 s_1=F_2 s_2## it...

Homework Statement Two spheres look identical and have the same mass. However, one is hollow and the other is solid. Describe an experiment to determine which is which. Homework Equations mgh= ½ m v^2 + ½ I ω^2 where I= 2/3 mr2 for a hollow sphere I=2/5 mr2 for a solid sphere The Attempt...

Homework Statement A rope of uniform mass per unit length ##\lambda## and length ##L## lies curled on a table, with a short length ##\delta l## of it hanging through a hole in the table. At time zero, the rope begins to slide through the hole. At what time ##t_c## (in seconds) does the end of...

Homework Statement [/B] A sphere of radius $1m$ and mass $25 Kg$ is put on another sphere of radius $5 m$ and $7 Kg$ which is placed on a smooth ground. Now the upper sphere is pushed very slightly from it's equilibrium position and it begins to fall. Now when the line joining the centre of...

Homework Statement Figure shows a massless wheel of radius R on which at a point a mass m is fixed and a uniform chain of mass 2m is tied to it which passes over the rim of the wheel and half of its length is hanging on other side as shown in the figure. When a small clockwise jerk is given to...