Conservation Definition and 999 Threads

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} =...

Hi all, I have a small misunderstanding about the energy conservation in diffraction from 2 slits. First, I understand the energy conservation of interference from 2 slits. If intensity from each slit is I, then I have intensity of 2I after slits plane. Interference is given by: So at bright...

Homework Statement Homework Equations m1v1+m2v2=m1v1+m1v1 after The Attempt at a Solution my answer = -1m1v1 because the wall is not moving so its velocity is 0 therefore m1v1 = m1-v1 after I put -v because it is the same just bounces in the opposite X direction I found somewhere...

Dear guys, Recently, i am confused with a problem in my textbook of mechanics. The question is, suppose there is a disk, placed horizontally, rotate about its center with angular velocity ω. A ball move with respect to the center of the disk in a trace of Archimedean spiral r=αθ. The angular...

Homework Statement sorry for the long question. Homework EquationsThe Attempt at a Solution I get everything up until it asks where the extra "half" of the power is spent. I do know that the extra half is referring to the "2" dK/dt. I have spent the last hour or so thinking about this...

Homework Statement 2. The attempt at a solution I set the initial angular momentum of the disk = to the sum of : rod's angular momentum, angular momentum of disk, rod's center of gravity and disk's center of gravity. With the reference point being at B. Why is the velocity of the rod's...

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 Indiana Jones standoff. Person A fires a 20g bullet at 500 m/s at Person B, who is holding a sword. The bullet sticks to the sword. The angular momentum of the sword is 2.225 kgm^2 / s. The moment of inertia about the center of mass of the sword is .7082 kgm^2. 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...

Homework Statement A solid sphere is rolling without slipping on rough ground with an angular velocity w and linear velocity v. It collides elastically with an another identical sphere at rest. Radius of each sphere is R and mass m. What is the linear velocity of the first sphere after it...

Referring to the Law of Conservation of Momentum: How is momentum always conserved? In a non-isolated system, an external force causes a change in momentum, so that initial momentum isn't the same as final momentum. Wouldn't this constitute a situation where momentum is not conserved? Or, is...

I know that the angular momentum is conserved in the below example, but intuitively I am struggling. Anyway, here goes! Homework Statement A bullet that is traveling without spinning hits and sticks into a filled disk tilted on its side an arbitrary distance "d" away from the center of mass...

Homework Statement In a pairs skating competition, the male skater is initially carrying his partner. Together they have a mass of 130.0 kg and they are are moving forward with a velocity of 2.5 m/s. If the male skater throws his partner forward at 1.5m/s, find the velocity of the male skater...

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...

Dear Experts, Total momentum of a system is said to be conserved in perfectly inelastic collisions also. I have a slight problem trying to comprehend a simple example regarding the same. If a small mass 'm' , say a ball is thrown at a huge stationary mass 'M' , say a wall. If the collision is...

Homework Statement A ball rolls at a velocity of 3.5m/s toward a 5.0kg ball at rest. They collide and stick and move off at 2.5 m/s. What was the mass of the moving ball?[/B]Homework Equations Pa + Pb = 0 M(a)V(a) = - M(b)V(b)[/B]The Attempt at a Solution So.. The ball at rest had zero...

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...

I've been a fan of this forum for a while, but never signed up for it, today I'm stuck on this problem and can't find anywhere other than Chegg but I don't have a premium account. 1. Homework Statement A meter stick is at rest on frictionless surface. A hockey puck is going towards the 30cm...

Homework Statement A basketball player shoots a 3-point shot. The 0.625 kg ball leaves the player's hands with a speed of 9m/s. It rises 2.4m before descending towards the basket. at the top of the ball's arc, what is its speed Homework Equations Im at a chapter named Energy and its...

Hi, In general relativity we have no general conservation of energy and momentum. But if there exists a Killing-field we can show that this leads to a symmetry in spacetime and so to a conserved quantity. Thats what the mathematic tells us. But I don't understand what's the meaning of an...

Homework Statement A 1500-kg sedan goes through a wide intersection traveling from north to south when it is hit by a 2200-kg SUV traveling from east to west. The two cars become embellished due to the impact and slide as one thereafter. On-the-scene measurements show that the coefficient of...

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 Hello, I am having trouble understanding the logic behind the solution to the posted problem. How did they deduce the equation for "Just after impact" ? I don't see how $$v_y = \sqrt{2g(0.6)}$$ What assumptions did they make or how did they get this simplified equation? I...

Take the case of Atwood machine, Where the masses of blocks are m and m,now,another ball of mass m strikes one of the blocks with a speed v and sticks to it. Considering our system as blocks+ball+string connecting the blocks(no pulley),can we apply conservation of momentum? Please explain...

Homework Statement A 3.60 kg block of copper at a temperature of 92 °C is dropped into a bucket containing a mixture of ice and water whose total mass is 1.50 kg. When thermal equilibrium is reached the temperature of the water is 5 °C. How much ice was in the bucket before the copper block was...

Homework Statement A car of mass 1500kg is parked on a 30degree slope before rolling down a distance of 30m onto a flat section where it collides with a stationary car. The cars stick together and scrape along the road for 20m until they come to a rest. Calculate the velocity of the two...

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...

Homework Statement 1. It has been argued that power plants should make use of off-peak hours (such as late at night) to generate mechanical energy and store it until it is needed during peak load times, such as the middle of the day. One suggestion has been to store the energy in large...

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...

Homework Statement A 48.0-kg boy, riding a 1.60-kg skateboard at a velocity of 5.80 m/s across a level sidewalk, jumps forward to leap over a wall. Just after leaving contact with the board, the boy's velocity relative to the sidewalk is 6.00 m/s, 7.40° above the horizontal. Ignore any friction...

Homework Statement A 226g block is pressed against a spring of force constant 1.25kN/m until the block compresses the spring 14.3cm. The spring rests at the bottom of a ramp inclined at 62.5° to the horizontal. Using energy considerations, determine how far up the incline the block moves before...

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...

Homework Statement Two carts sit on a horizontal, frictionless track; the spring between them is compressed. The small cart has mass m, and the mass of the larger cart is M = 4.65m. NOTE: Every velocity needs magnitude and direction (given by the sign). a) Suppose the carts are initially at...

Homework Statement A 70.0-kg man and a 55.0-kg woman holding a 2.50-kg purse on ice skates stand facing each other. (a) If the woman pushes the man backwards so that his final speed is 1.50 m/s, with what average force did she push him, assum ing they were in contact for 0.500 s? (b) What is...

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...

[Moderator's note: thread spun off from a previous one on a related but different topic.] Well that's another question that has been puzzling me for quite some time and would love to know the answer to it... Imagine 4 tubes of equal length, making a square, with 4 identical photons running...

If the 3-momentum γmu and energy γmc2 are conserved in one frame, they will be conserved in any other frame. But I was thinking about RoS, since events may not happen simultaneously in another frame, will 3-momentum and energy always be conserved with respect to time?

The question is: When a large car collides with a small car, which one undergoes the greater change in momentum: the large one or the small one? Or is it the same for both? I wanted to plug in dumb numbers: m_tv_{ti} + m_cv_{ci} = m_tv_{tf} + m_cv_{cf} lets assume the truck has a mass of...

Homework Statement Find the horizontal distance the skier travels before coming to rest if the incline also has a coefficient of kinetic friction equal to 0.210. Assume that theta = 20.0°. Homework EquationsThe Attempt at a Solution

What happens to the energy of a laser beam when it completely deconstructively interferes with itself in a michelson interferometer?

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 Attached figrue shows an 8.00 kg stone at rest on a spring.The spring is compressed 10.0 cm by the stone. (a) What is the spring constant? (b) The stone is pushed down an additional 30.0 cm and released.What is the elastic potential energy of the compressed spring just...

Hello everyone, Why don't neutral particle oscillations have to obey conservation of (quark) flavor quantum numbers, with the example of neutral Kaon oscillations?

Hello everyone, Are neutrino flavors conserved in interactions other than neutral particle oscillations?

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...

Homework Statement Starting from rest, two identical boxes are pushed through the same distance. Box A experiences a force F, while box B experience a force 2F. What is true about their final speeds?- The final speed of box A is twice that of box B. - The final speed of box A is equal to that...

Homework Statement A 100 kg person in space throws a 1kg sphere away from their body. The sphere starts from rest and ends up traveling 10 m/s away from the person. What is the kinetic energy of the person and the kinetic energy of the sphere? Is kinetic energy conserved?[/B]Homework Equations...

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...