Energy conservation Definition and 434 Threads

Homework Statement find max height of a projectile traveling at 40 m/s 60 degrees from the horizontal using conservation of energy Homework Equations KEi + PEi = KEf + PEf? The Attempt at a Solution couldnt attempt. (I know I can't be given the answer, but even just the proper...

Homework Statement Homework Equations K_{1}+U_{1} +W_{nc} =K_{2} + U _{2} (The subscript coding is not working right, but they ARE suppose to be subscripts and nothing is squared) Work on the spring = .5kx_{2} - .2kx_{2} (final minus initial) The Attempt at a Solution I didnt...

Homework Statement A block mass M slides down the side of a frictionless circle Radius R. At an angle Theta the mass M flies off the circle, what is the angle? Homework Equations PE(top) = KE(point it flies off) + PE(at that point) Arad = V^2 / R Sum Of Forces = Mass *...

Hi everyone, so I was going to start on my HW but there was some things confusing me when reading the book. This is calculus based (feel free to use integrals) and we are on the concept of potential and total mechanical energy and such.1) This new chapter we are on introduces Work_{grav}=mgh_{1}...

Homework Statement A rocket uses a photon radiation engine. Knowing that from a reference R the initial and final rest masses of the rocket are Mi and Mf show that Mi / Mf = sqrt [ ( c + v ) / ( c - v ) ] and that the rocket was initially resting on R Homework Equations Total...

Homework Statement Two particles of masses M1 = 81000 kg and M2 = 9400 kg are initially at rest an infinite distance apart. As a result of the gravitational force the two masses move towards each other. Calculate the speed of mass M1 and mass M2 when their separation distance is 26.5 km...

The photon comes in with momentum p and leaves with the same momentum in the opposite direction. The sail picks up a momentum of 2p in the original photon's direction. Energy conservation states that: h\nu_1=h\nu_2+\frac{(2p)^2^}{2m}=p_{1}c=p_{2}c+\frac{(2p)^2^}{2m} Isn't |p1|=|p2| thus...

in non inertial frames , a pseudo force act on the bodies but is the work done by this force is real? if it is ,will the law of energy conservation hold in non inertial frames too , as everything is gaining velocity due to pseudo acceleration.

my question is, when using energy conservation when do i put the potential energy of gravity negative? if its under where it set my potential energy to 0? or am i wrong, is gravity's potential energy always positive (except at my set u=0 point) ? can someone explain this to me, having trouble...

two massive particles a finite distance from each other are bound to each other gravitationally, so if one disappeared the other one would have its energy altered, and the conservation of mass-energy would be broken. so what happens when a massive particle decays to a less massive particle...

My physics textbook states the following about a single loop circuit with a resistor and ideal battery. "From the principle of conservation of energy, the work done by the (ideal) battery must equal the thermal energy that appears in the resistor" Can anyone explain why energy must be...

If the crest of one light wave meets the trough of another light wave of the same frequency and intensity they supposedly cancel each other resulting in no light (e.g., the dark areas that result on the screen when both slits are open on a dual slit experiment). In particle physics, why then...

Hello, http://fm92-1.com/physics.jpg" The initial speed is 0 m/s We let go of the rope What is the system's kinetic energy when the little block is at 15 cm from the ground? What's wrong with my work? E_{t}=E_{P}+E_{F}+E_{K}\Rightarrow E_{K}=E_{t}-E_{P}-E_{F} where Et is total energy...

Hello, I have one problem... In what initial speed must barmen throw beer mug on the table so it can travel 2 meters. Mass of the beer mug is 0,3 kg. Sliding loss factor between table and beer mug is 0,3. I hope you have understand the question, because I am translating it from my mother...

I've seen many times people argue as follows: "Energy must be conserved, because otherwise the first law of thermodynamics would be violated." Clearly, such arguing is logically incorrect. The energy conservation law is much more general and fundamental, while the first law of thermodynamics is...

Homework Statement This is regarding a Fabry-Perot Interferometer with identical mirrors: If you shine a beam of light on a 99% reflecting mirror, 1% goes through and the other 99% is reflected. But if a second mirror is placed behind the first one, where there is only 1% of the light...

[SOLVED] Energy Conservation Problem Please HELP!:) Homework Statement A 2.3-kg block slides along a frictionless horizontal surface with a speed of 5.9 m/s After sliding a distance of 6 m, the block makes a smooth transition to a frictionless ramp inclined at an angle of 24o to the...

Hello everybody. I apologize if this question is a little trivial compared to a lot of the threads posted, but I am an 8th grade science physical science teacher and am a little confused about some of the material. From what I understand, if an atom absorbs a photon of energy E, then an...

A thin, unirform rod (I=1/3ML^2) of length L and mass M is pivoted about one end. A small metal ball of mass m=2M is attached to the road a distance d from the pivot. The rod and ball are realeased from rest in a horizontal position and allowed to swing downward without friction or air...

This is Problem 10.46 from the Engineering Physics Book by Knight. A vertical spring with k = 490 N/m is standing on the ground. You are holding a 5.0 kg block just above the spring, not quite touching it. a.) How far does the spring compress if you let go of the block suddenly? b.)...

1. Jane, whose mass is 49.0 kg, needs to swing across a river filled with man-eating crocodiles in order to rescue Tarzan, whose mass is 80.0 kg. However, she must swing into a constant horizontal wind force F on a vine that is initially at an angle of with the vertical. (See Fig. P5.73.) In the...

If electrons conserve energy, why they don't stop to move? Thanks.

Homework Statement A massless spring of spring constant 20 N/m is placed between two carts. Cart 1 has a mass M1 = 5 kg and Cart 2 has a mass M2 = 2 kg. The carts are pushed toward one another until the spring is compressed a distance 1.5 m. The carts are then released and the spring pushes...

Energy can be neither created nor destroyed. What is energy?. ability to do work. what is work ? work = force x displacement. Consider a body of mass 'm' moving at a uniform velocity 'v'.work done here is zero(no acceleration).So energy is zero. DONT SAY KINETIC ENERGY is there.please check...

1. A toy gun fires a 9.41-g projectile disc by using a compressed sprint (k=1.72 x 10^3 N/m) and a 13.1 cm long barrel. As the disc travvels through the barrel it experiences a constant frictional force of 0.13 N. If the spring is compressed 14 mm what is the speed of the disc as it leaves the...

Homework Statement A car moving with an initial speed v collides with a second lighter stationary car that is 58.3% as massive. After the collision, the two cars stick together and move off in the same direction as before. Calculate the final speed of the two cars after the collision. Give...

Homework Statement There is a ring which radius is R. A little ball moves inside this ring. Ring's plane is perpendicular to the surface of ground. When a ball is moving inside a ring (ring is in quiet), the ball reaches a height which is equal to R/2. The ring starts to move upright with a...

Homework Statement Here is the drawing which shows the situation: http://img507.imageshack.us/my.php?image=drawingae3.jpg The mass of each ball is equal to m. A rod which connects the balls is weightless. A vertical wall affects a ball which is below with force F. I need to find this...

Suppose in space you have a hydrogen gas cloud that is collapsing into a sphere under its own gravity. Pressure and heat rises due a decreased volume and gravity trap. Let's say the gas cloud is not going to reach fission and won't become a sun, so it's a gas giant. My question is under...

Canadian government tries to make energy conservation "hip" http://www.flickoff.org/ get it?? FLICK OFF! as in flick off the lights and save energy! but omg! it looks just like F**K OFF... NOT! I'm so amused!... TO THE X-TREEEME! O HELLZZZ YEA! THAT'S OUR SUPER RAD ENVIRONMENT MINISTER...

"Simple" part of a hard problem involving momentum/kinetic energy conservation Two balls, of masses mA = 36 g and mB = 64 g are suspended as shown in Figure 7-44. The lighter ball is pulled away to a 60° angle with the vertical and released. (a) What is the velocity of the lighter ball before...

When we look at a particle's rest frame its energy is Mc^2. But the particle decay has some width, so the products of the particle,generally, will have total energy different than Mc^2. How can it be, is there no energy conservation?

Hi guys - Here's the problem I am chewing on: A binary star system consists of two stars, each equal to the sun in mass. The distance between the two stars is 1.0 X 10^12m. A comet which is essentially at rest, begins to make its journey toward the binary star system as a result of...

Homework Statement Consider an isolated system comprising two particles of masses m1 and m2, whose position vectors, in an inertial frame, are x1 and x2 and whose velocity vectors are v1 and v2. The interaction of the particles may be described by an energy function E = 1/2 m1v1^2 + 1/2...

Homework Statement A 900-kg two-stage rocket is traveling at a speed of 6.50 x 10^3 m/s away from Earth when a predesigned explosion separates the rocket into two sections of equal mass that then move with a relative speed (relative to each other) of 2.80 x 10^3 m/s along the original line of...

Hello, I'm new here so please let me know if I do something wrong. 1. Problem 1 1. A skier of mass M starts from rest at the top of a solid sphere of radius R and slides down its frictionless surface. At what angle will the skier leave the sphere...

Not able to really find an already existing thread where my question could fit in very well, I am starting this new thread which I hope is not too much confusing. Conservation of energy of photons in an expanding vacuum part of the universe? The wavelength of a photon traveling through the...

The maximum speed of a child on a swing is 4.9 m/s. The child’s height above the ground at the lowest point is 0.7 m. How high above the ground is he at his highest point? http://img208.imageshack.us/img208/9949/untitledyx0.png Above is the work done to solve the problem. I don't understand...

The four wheels of a car have each a mass of 25kg and a radius of 30cm. The car's mass is 1000kg. We neglect the losses due to friction. We assimilate the wheels to homogeneous cylinders. a) What is the total kinetic energy of the car and the wheels if the speed of the car is 30m/s. b)...

This is a multiple part problem but I'd like to have some help on one part at a time. Here is the general question: A pulley with a radius of R=0.50m and a mass of M=4.0kg is mounted on a frictionless axle. The pulley is a uniform solid disk with a rotational inertia of I=1/2MR^2. A block...

grrr... gravity A rocket is launched straight up from the Earth's surface at a speed of 1.90×104 . What is its speed when it is very far away from the earth? plugging everything into the energy conservation theorem i came up with the exact same speed... I'm not sure what I'm doing wrong.

An 1kg object is sliding down a 4m high incline which is inclined at 53 degrees. The initial speed is 2m/s. It then slides on a horizontal section 3m long which is at ground level and then slides up an incline plane that is inclined at 37 degrees. All surfaces have a kinetic coefficient of uc =...

Hello all, On our test today the question said, "An 2 Kg object is moving along the x-axis and explodes, with particle 1, 1 Kg, shooting north at 3 m/s, and particle 2, 1 Kg, traveling 30 degrees north of east at 5 m/s. What was the initial velocity of the object?" Now I was talking with...

http://www.physics.auburn.edu/~boivin/homework9.htm "A bullet of mass m and speed v passes completely through a pendulum bob of mass M. The bullet emerges with a speed of v/2. The pendulum bob is suspended by a stiff rod of length l and negligable mass. A) What is the minimum value of v...

A block is susoended from the end of a spring. The spring is hanging off the ceiling. An external force holds the block so that, initially, the spring is not stretched or compressed. When the block is released, it oscillates up and down between positions A and B. If the mass of the block is...

Hi, I've been struggling with this problem and would appreciate any help: A 1.8 kg block slides down a frictionless ramp, as shown in Figure 8-28. The top of the ramp is 1.5 m above the ground; the bottom of the ramp is h = 0.20 m above the ground. The block leaves the ramp moving...

This problem has a picture with it so I posted at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=21023924&imageID=1304590013 The problem is problem number 8. How do I approach it? I have no idea what to do.

A stone of mass m is thrown straight up into the air with speed v_o. While the flight it feels a force of air resistance of magnitude f. Determine the speed of the stone when it hits the ground. You will need to combine energy conservation equations for the upward and downward parts of the...

My professor insists on lecturing about tension and pulleys all week, then he assigns us problems that have no relation to lecture :rolleyes: I'm having trouble with a few problems, hopefully you can help me. Grant Hill jumps 1.2 m straight up into the air to slam-dunk a basketball into...

Hi, A rather simple question that I just can't seem to solve: The greatest instantaneous acceleration a person can survive is 25g, where g is the acceleration of free fall. A climber's rope should be selected such taht, if the climber falls when the rope is attached to a fixed point on a...