Conservation of energy Definition and 1000 Threads

A child whose weight is 267 N slides down a 6.10 m playground slide that makes an angle of 20.0° with the horizontal. The coefficient of kinetic friction between slide and child is 0.10. (a) How much energy is transferred to thermal energy? (b) If she starts at the top with a speed of 0.534...

Conservation of energy, PE & KE problem. help?? a block is sent sliding down a frictionless ramp. Its speeds at points A and B are 2.00 m/s and 2.60 m/s, respectively. Next, it is again sent sliding down the ramp, but this time its speed at point A is 4.00 m/s. What then is its speed at point...

A 4 kg bundle starts up a 30° incline with 128 J of kinetic energy. How far will it slide up the plane if the coefficient of friction is 0.30? So the solution to the problem is 128 = 4(9.8)(x)(sin30) + 0.30 (4)(9.8)(x)(cos30)...x = 4.29m I don't understand the solution. so 128 =...

The string in the Figure is L = 120 cm long, has a ball attached to one end, and is fixed at its other end. The distance d to the fixed peg at point P is 75.0 cm. When the initially stationary ball is released with the string horizontal as shown, it will swing along the dashed arc. What is...

Homework Statement The string in the Figure is L = 113.0 cm long and the distance d to the fixed peg P is 91.5 cm. When the ball is released from rest in the position shown, it will swing along the dashed arc. How fast will it be going when it reaches the lowest point in its swing? B-How...

Homework Statement Assume there is no air friction. A ball of mass m = 3.39 kg is dropped from rest at height h = 1.51 m. It hits the ground, losing energy ΔE = 1/11 of its total energy in the collision. How high will the ball bounce upward before it comes momentarily to rest? Homework...

Homework Statement A skier (m=55.00 kg) starts sliding down from the top of a ski jump with negligible friction and takes off horizontally. (A)If h = 6.80 m and D = 10.20 m, find H.(B)Find her total kinetic energy as she reaches the ground. Homework Equations KEi+PEi=KEf+PEf (law of...

Homework Statement A large punch bowl holds 3.00 kg of lemonade (which is essentially just water) at 1.00 degree celsius. A 0.055 kg ice cube at 0 degrees is placed in the lemonade. What is the final temperature of the system? Homework Equations Q=mcΔT Q=mL The Attempt at a...

If I were to pump water from my well (at my house) into the pressure tank that we have, it would require a certain amount of work. If I then turned on my faucet and had a small turbine generating an electric current, would that electric current (which I realize would be small, this is more for...

Suppose that I hold a Yo-Yo and then I leave it to fall [and of course rotate] holding only the string. I seems to me that the energy [not the whole of the potential energy will be converted to (1/2)mv^2+(1/2)I\omega^2] is not conserved, because of the force the string applies on the Yo-Yo. Is...

Okay consider this system one dimensional system: We have a positive charge at the origin. Far out at infinity on the x-axis we have a positive charge and at minus infinity on this minus x-axis we have a negative charge. For simplicity we will assume that the plus- and minus charge do not...

Homework Statement A satellite moves around the Earth in a circular orbit of radius r. (a) What is the speed vi of the satellite? (b) Suddenly, an explosion breaks the satellite into two pieces, with masses m and 4m. Immediately after the explosion, the smaller piece of mass m is stationary...

Lets say we had a light source. It takes energy and turns it at some efficiency into light. You put the light source on say, a white dwarf. The light source, still at the same efficiency, produces light that is gravitationally redshifted and therefore lost energy. What happened to the...

Homework Statement Using formulae for PE and KE, find the speed that a tennis ball hits the ground when dropped from 20m. Homework Equations m x g x h and 1/2 x m x v^2 The Attempt at a Solution PE=KE Mgh = 1/2mv^2 (masses cancel out) 9.8 x 20.= 1/2 v^2 196 = 1/2 v^2 196/...

Homework Statement Using the formulae for potential energy and kinetic energy, find the speed that a tennis ball hits the ground when dropped from a height of 20m. With reference to the principle of conservation of energy, explain why you could use these equations and what assumptions you...

Think of two torus-shaped tubes. Each tube is filled with electrically-charged ping pong balls. The inside of the tube is smooth and friction-less. So someone gives the ping pong balls inside a push, and the balls start moving in a circle. The same thing happens in the 2nd torus...

Just a question. I'm just getting back into re-learning my physics, and learning physics I never had a chance to study. But...Do you know?... If two atoms - with velocities - collide and recoil, how much energy is lost from their velocities/momentum? Is there a formula?...Does it have...

Homework Statement i attached the problem since its easier. Homework Equations im not sure. i know the equation for h has to be included. but I am not sure what other equations must be used. The Attempt at a Solution I honestly don't know how to begin. Any kind of help would be...

Suppose you are trying the solve the equation of motion of say a particle constrained to move on a surface f(x\vec{},t)=0. The equation of motion is: mx\ddot{} = F\vec{} + N\vec{}, where F is an known external force and N is the unknown constraint force. Now, when you assume that N always...

Suppose i have a ball of mass m and if i left the ball at a particular height 'h', then i have done some work on it or by the law of conservation of energy i have transferred some energy to the ball. Now suppose i release the ball isn't the energy that i have transferred changing because it...

Hey guys. I was wondering, if energy cannot be created or destroyed as stated in the conversation of energy, then where did energy come from in the first place?

Suppose a rocket is hovering above the moon at a constant height, burning just enough propellant to stay at that height, and not move upwards or downwards. Viewed from an inertial frame, we have. Initial energy (just before ignition) : 1. Gravitational potential energy between rocket and...

according the principle of superposition, a wave with a certain amplitude superposed with a similar wave will yield a wave with 4 times the amount of energy. This would be double the combined energy of the original 2 waves. Assuming 2 point wave sources are perfectly in phase; and there is no...

hi, 1- if the universe total energy is zero, is this mean that the universe can come from (zero energy + zero energy = 0 ) to (negative energy + positive energy = 0 ) 2- if in a system of the total energy is (E - E = 0) does the conservation of energy allow a system to change to (2E...

Hallo, I understand in a system energy is transformed from one form to another... Although I'm wondering is it possibile to get more energy "OUT" as in? Imagine this simple equation: Ein = Eout Eout: would usually be less than "Ein" due to losses going for heat,frictions,sound,etc...

Hi All, First off, thanks to all the old hands at physicsforums, you guys are truly an amazing resource. I was thinking about a system today that at first glance, appears to violate local conservation of energy for two mechanical wave pulses interfering with each other. Consider a...

The first law seems obvious, plug in 0 for acceleration and you get 0 force. Therefore for something to accelerate there needs to be some net force. Also, wouldn't the third law have to be true if energy is conserved at all times? Sorry if this has been asked before.

Please help me with the attached question. I don't understand how you get from the first line to the second line in (2). (I'm not too familiar with working with cross products and vectors). Also, I don't know how you get (5) from (1) and (2). Any help would be much appreciated. Thanks! :)

Hi all, I have a question about the Unruh effect and energy conservation; I'd originally asked part of this in another forum, but I thought it might be more appropriate to post here. I understand that, as per the Unruh effect, a uniformly accelerated observer and an inertial observer...

I would like to better understand the nature of gravitational attraction and the law of conservation of energy. Imagine you measure inertial mass (using inertial ballance) of an object far from a gravitating mass which is at rest relative to the object. Then you release the object and let it...

Hallo everyone. I had a equation about energy in a form of "rotational kinetic energy". Imagine this situation with me so I can explain the question I'm trying to get at: Let say I had a rotating wheel that is connected to other wheels directly... I supplied 1000J(simple number for me to...

The first law of thermodynamics states that dU = -PdV + dQ We can apply this to the expansion of the universe by assuming the expansion of space is a adiabatic process, i.e. dQ = 0. Together with the FW metric, we end up with one of the Friedman Equations: \dot{\rho} = -\frac{3\dot{a}}{a}(p +...

Homework Statement A large ball bearing is suspended as a pendulum. One end of the pendulum is held by the electromagnet (1) and the ball is initially held by magnet (2) at some height, h, above its lowest position. The ball is released from (2) and as the pendulum swings through the vertical...

Homework Statement This isn't really coursework or homework, but something I really want to confirm. There is a ramp of height h on an angle θ that a car is placed on that leads to a wall perpendicular to the ground (looks like this: |∠). When calculating velocity of the car when it hits...

Elastic Potential Energy with Spring and Incline (Diagram Included) Homework Statement Homework Equations ET = 1/2(m)(V2) + mgh + 1/2k*x2 The Attempt at a Solution ET1 - Wf = ET2 1/2k*x2 - Wf = mgh + 1/2mV2 where, Wf = [(0.53)(2kg)(9.8m/s2)(cos67)](1.3m+0.4m) ^ I used this...

Homework Statement A vertical Spring (ignoring mass) whose spring constant is 875N/m is attached to a table and is compressed down by .160m. What upward speed can it give to a .350kg ball when released? How high up its original position will the ball fly? Homework Equations Spring...

Mechanics--Angular Motion and Conservation of Energy Homework Statement A uniform bar of mass m and length L is pivoted at one end and is held vertically above the pivot. After the bar is released, it swings downward and clockwise with no friction in the pivot. At the instant the bar is...

Homework Statement A sphere rolling with an initial velocity of 30 ft/s starts up a plane inclined at an angle of 30o with the horizontal as shown. How far will it roll up the plane before it rolls back down? Homework Equations T_1+V_1=T_2+V_2 The Attempt at a Solution We are...

I apologize in advance for my lack of knowledge of "physics english". First off, this is high school level. :) I'm terribly sorry if this is confusing due to my lack of understand of the subject, the metric system, and my lack of grasp for the English language as well as terminology. What...

So I have another problem that I'm having some issues with. Homework Statement A ball attached to a massless rope is allowed to swing around a circle of radius r=0.8m. When the ball reaches point B, the horizontal rope hits the peg P causing the ball to swing around a smaller circle...

Hi How does Lenz's law obey the Law of Energy Conservation? I know it has to but I really don't get it. Thanks Salil

A ball is released on the inside surface of a half-pipe. The left side of the pipe is rough, so that the ball rolls there without slipping. The right side of the pipe is coated with frictionless ice. If the ball is released from a height h on the left side, how high will it go on the right side...

1) \frac{1}{2}mv^{2}_{2}-mgy_{2} = \frac{1}{2}mv^{2}_{1}-mgy_{1} 2) \frac{1}{2}m(v^{2}_{2}-2gy_{2}) = \frac{1}{2}m(v^{2}_{1}-2gy_{1}) since g = \frac{GM}{R^{2}} and \frac{1}{2}m cancels. 3) v^{2}_{2}-2\frac{GM}{R^{2}}y_{2} = v^{2}_{1}-2\frac{GM}{R^{2}}y_{1} 4) v^{2}_{2}-v^{2}_{1} =...

I have just recently completed a lab in Conservation of Energy. My course is through correspondence, so my labs are virtual. I noticed that the heavier the ball was, the haters the total energy dropped as the ball continued to bounce. Now I understand that energy can be transferred into many...

Homework Statement You are asked to design a spring that will give a 1130 satellite a speed of 1.90 m/s relative to an orbiting space shuttle. Your spring is to give the satellite a maximum acceleration of 5g. The spring's mass, the recoil kinetic energy of the shuttle, and changes in...

Homework Statement A spring of negligible mass has force constant K = 1700 n/m A book of mass 1.30 kg is dropped from a height of .7m above the top of the spring. Find the maximum distance the spring will be compressed. Homework Equations PEi + KEi = PEf + KEf PEgrav = mgy...

My guess is that they don't since it's thought that they might be possible, but here's why I'm asking this question: in the magnetic field created by a magnetic dipole, couldn't you place a magnetic monopole into the field (make sure it stays on the set path) and have it circulate continuously...

While researching dark matter and dark energy, I came across the following passage on NASA's website: "The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a...

Homework Statement A kid on a sled slides down a hill from a rest position. m=47.0kg vertical displacement is 10.0m Homework Equations a)For total mechanical energy I calculated (Egravity=mgh) to equal 46 x 10^2 J b)*mentions we assume there is no friction or external pushes* and...

I attached the problem. The solution is of the form: .5*(5/32.2)v^2+.5(10/32.2)(12/18*v)^2 + 5*18/12*sin(60)-10*12/12*sin60=0 I don't understand why they put the radius in the kinetic energies like the 12/18 part. I know you have to do that, but I don't understand why.