Lost Definition and 564 Threads

Hey I am doctorwes and I am a A2 student in Maths, Physics and ICT Recently, I have been feeling rather cr*p towards my work in both Maths and Physics. I mananged to get a B in our maths assessment, on which I should have got 90 percent or more and now I have got my physics paper back and I...

Homework Statement 90 grams of water at 75°C are mixed with an equal amount of water at 25°C in a completely insulated container. The final temperature of the water is 50°C. How much heat is lost by the hot water? Homework Equations The hot water drops to 50 degrees Celsius so it has...

1. The problem statement. Two boys are sliding toward each other on a frictionless, ice-covered parking lot. Jacob, mass 45 kg, is gliding to the right at 7.98 m/s, and Ethan, mass 31.0 kg, is gliding to the left at 10.7 m/s along the same line. When they meet, they grab each other and hang on...

Homework Statement A particle begins at rest on a circular track and is subjected to a constant angular acceleration of magnitude α beginning when t=0s.(a) Show that the magnitudes of the tangential and centripetal accelerations of the particle are equal when t=(1/α )^(1/2) Independent...

I have recently posted about trying to enter a masters/phd program for Medical Physics (Going to try for SDSU and LSU). Before this week i was quite hopeful and naive i suppose. I was not aware of how tough the job market was and the bottlenecking in the residency programs. Don't get me...

I'm not a native English speaker, and this assignment wasn't originally in English, so I had to translate it to English, thus the grammar errors, but hopefully it's understandable) ----------------------------------- For an investment in an equity assessed in general to be the following...

~Electrodynamics~ Potential from charged sphere. I am lost :/ Homework Statement A sphere of radius R, centered at the origin, carries a charge density ρ(r,θ)=κ/r^2(R-2r)sin^2(θ). κ is constant. Find exact potential. Homework Equations 1/4∏ε∫ρ∂t/r The Attempt at a Solution Question and...

Homework Statement A small city requires about ##17 \mbox{MW}## of power. Suppose that instead of using high-voltage lines to supply the power, the power is delivered at ##120 V##. Assuming a two-wire line of 0.60cm -diameter copper wire, estimate the cost of the energy lost to heat per hour...

Hi, I recently did a homework problem for my introductory Quantum Mechanics course and in the problem we were given the sun's temperature in Kelvin as well as the diameter of the sun and instructed to calculate the rest mass lost per second to radiation by the sun. I was able to solve the...

Homework Statement Homework Equations I know that energy mentioned in the statement is kinetic energy so keep in mind when reading that ##E\equiv E_k##. In our case the kinetic energy is larger than the potential energy ##\boxed{E>E_p}## and this is why stationary states for the regions 1...

Consider the following. You have an electron of negative charge orbiting a proton of positive charge at some distance R (i.e. a classical hydrogen atom). I understand the hydrogen atom is unstable under classical physics because the accelerating electron loses its kinetic energy as...

Hello everyone:(Please forgive my poor English.) I've been learning many-body theory for a year or so, however, I'm quite confused with different Green's functions (GF) there. One of the most things I want to get clear is about zero-temperature GF and imaginary-time GF (or Matsubara GF), both...

Hello everyone. Before I start asking my question, I'd like to, if I may, talk about myself. I'm currently studying Aeronautical/Aerospace engineering and the following year will be my third year(including undergraduate preparotry). But, I don't really want to be an engineer, but a mathemetician...

Homework Statement A physicist pours 100g of water at 100'C into a 20g aluminium cup which already contains 50g of water at 20'C. The final equilibrium temperature of the water is 71.847. C(water)=4186J/kgC C(aluminium)=900J/kgC 1. the amount of heat lost by the hot water 2. the amount...

Homework Statement Initially, a planet with mass m moves on a circular orbit (r = R) around a star with mass M. Now M is instantaneously decreased to M'. Find the eccentricity e of the elliptical orbit the planet now follows. Homework Equations specific angular momentum l = L/m...

This thread is a present for Evo's birthday :smile: There was some media coverage of Heracleion here and here the other day. Check out the links, awesome photo's. However the global sea level rise in the last 3000 years was maybe three feet, so only 15 feet would be accounted for...

1. Two carts, each of mass M, travel towards each other on a frictionless air track, one with velocity V, and the other with -3V. They collide and stick together. How much kinetic energy is lost in the collision? 2. P = mv, KE=1/2mv2 3. Initial KE of the system is the sum of the kinetic...

Finally, something being done for homeowners that lost their homes without proper evaluation. http://news.yahoo.com/us-banks-send-checks-4-153752525.html

Homework Statement Find the kinetic energy lost Homework Equations The Attempt at a Solution We solved it in class Ek1 = -206 J Ek2 = 10 J Find the energy lost. The answer is was 2.2 * 10^2 J lost This is confusing for me, to find energy lost, we should subtract the...

Hey guys, I'm trying to complete a homework problem, but I'm not quite sure how to approach it. Here is the question: A 90.5-kg fullback running east with a speed of 4.91 m/s is tackled by a 94.7-kg opponent running north with a speed of 2.93 m/s. Determine the mechanical energy that...

Homework Statement E& M Purcell, 3.11 A 100-pF capacitor is charged to 100 volts. After the charging battery is disconnected, the capacitor is connected in parallel to another capacitor. If the final voltage is 30 volts, what is the capacitance of the second capacitor? How much energy...

Homework Statement These are two problems my professor has given me to do. I'm not very good at physics and could use a little help. 1. Sir Killalot's foe Dead Metal is due north of Sir Killalot's position and at a distance of 12m. Dead Metal moves 15m at an angle of 30 degress to a new...

Imagine two bodies A & B. they have same mass and same speed, but they are traveling in different direction. the kinetic energies of both the bodies is equal (1/2*mv^2), because they have same speed and mass. now they collide each other. As they have same mass and speed they both stop. now the...

I read that matter-antimatter annihilation is not as useful as we thought because a large amount of energy is carried away by neutrinos. So, how much is this energy ? What is the percentage of the lost energy to the energy calculated from E=mc^2 ?

Homework Statement We have to make a roller coaster for our school project. This coaster starts with a spring. In this coaster, there is a collision. Essentially, I need to find the energy lost at the collision, and the average force of friction. Homework Equations Em1=Em2 W=Fd F=ma A=DELTA v/...

I've never heard it said before but it appears to me that all electrical current that flows in a solid state component system; processors, diodes, transistors, resistors, etc. is eventually dissipated as heat. What are your thoughts about this?

Could anyone clarify where is gone the energy lost by CBR as the universe expands? Thank you in advance and happy new year

I'm a 4th year physics student in the EU. Over the course of my undergrad degree I developed an unbalanced lifestyle to pull through the degree and learn as much as I could, with hopes of going to graduate school to do astrophysics research. I gave up on regular exercise and hobbies in my 2nd...

How much mass is lost in a single D + T= 4He fusion reaction? And is all of the mass lost converted to energy or just some? The mass lost can be converted to energy using e=mc2.

Hello all, I'm new here. I'm at a point in life and in school where it's difficult to discern where I'm heading and what I should expect out of myself academically and professionally in the next few years. I'm 23 years old and I didn't realize until the age of 21 what it was that I was...

My wife lost a file that she worked directly from a flash drive. Somehow, the whole folder disappeared. Is there any way to recover that folder? Problem is she did not work off the C drive where even you accidentally deleted it, you can find it in the trash bin. She worked directly off the...

Homework Statement How many terms are in each sequence? 12, 4, 4/3, ..., 4/729 Homework Equations The Attempt at a Solution using tn=t1(r)(n-1) ? I am lost

Homework Statement So there's a particle of mass 4u that strikes another particle of mass 196u. The collision is elastic. What percentage of its original kinetic energy has the moving particle lost? Homework Equations m1v1o + m2v2o = m1vf + m2v2f K1o + K2o = K1f + K2f The Attempt...

Homework Statement a 50 g bullet hits and becomes embedded in a wooden block of as 450 g which is at rest on a surface (μ = 0.41) and is attached to a spring bumper. The block and bullet compress the spring bumper a distance of 20 cm. Is the spring constant is 250 N/m find initial speed of...

if you have a magnet that pulls 40lbs of force if you broke that into 2 how much force will each magnet pull. i have some neodymium magnets from hardrives and i want to break them up but i want to know if that's gunna make them lose a lot of force. anyone know the formula for calculating...

A cyclist has a speed of 5 m/s when she beings to coast down a hill, as shown in the figure. At the bottom of the hill, her speed has increased to 12m/s. the mass of the cyclist plus bicycle is 75kg. a) Calculate the work done by gravity on the cyclist and bicycle. b) Calculate the...

Introductory Bohrs Model Problem...and I'm Lost! Ok, so I "think" what I am trying to find here is the frequency of the energy between two states of energy. I admit that part of my problem probably lies in the fact that I'm not even sure what it is I'm trying to find. My class seems to be just...

How can there be different types of infinities? I just learned that cardinality of set of natural numbers, integers, prime numbers is alepho. Why are we replacing infinity with a number i.e. alepho. And what further blows my mind is that cardinality of real numbers is also infinity but a...

I'm LOST! Car is suppose to overtake truck but at what velocity? two cars C and D move in the same direction in parrallel lanes of a straight road. C starts from rest and begins to move with a constant acceleration. at that instat the C begins to move it is overtaken by D, which is moving with...

Homework Statement In the circuit shown in the figure each capacitor initially has a charge of magnitude 3.00nC on its plates. A) After the switch S is closed, what will be the current in the circuit at the instant that the capacitors have lost 80.0% of their initial stored energy...

If a particle (let's call it Z) is happily minding it's own business, and a particle-antiparticle pair spawns in it's vicinity (let's call them particle A and B, created from 'zero point' energy), and it just so happens that the antiparticle (let's say B) collides with particle Z before it is...

Homework Statement I am reviewing some trig, and I forgot how to do this. Please let me figure this one simple thing out. Here is the questions. Find the exact trig ratios of 5∏/6 Ok, now look at my diagram below to see where I am having trouble with! What simple process am...

Homework Statement There is a tube attached to a board in a fashion that a ball can be dropped in the top and the tube curves to the right 90°. If a ball of mass 7.6g is dropped into the top of the tube, what is the minimum height the exit point of the tube needs to be in order for the ball to...

Homework Statement You fire a light signal at 60° north of west. (a) find the velocity components of this signal according to an observer moving eastward relative to you at 0.5c. From them, determine the magnitude and direction of light signal's velocity according to the other observer. (b)...

Homework Statement Planet W is 12ly from earth. Anna and Bob are both 20 years old. Anna travels to planet W at 0.6c, quickly turns around, and returns to Earth at 0.6c. How old will Anna and Bob be when Anna gets back? Homework Equations The Attempt at a Solution I've tried...

Homework Statement Much of the of heat lost from a cross-country skier's body is radiated from the head, since it is often uncovered. Treat a head as a 20-cm-diameter, 20-cm-tall cylinder with a flat top. If the surface temperature of a body is 35 C, what is the net rate of heat loss on a...

[b]1. i am given a matrix A= 1 0 2 1 1 1 3 1 2 3 8 -2 -3 3 -5 1 and then it asks why do I know that span {a1, a2, a3, a4} are a subset of R^4. Homework Equations The Attempt at a Solution Is it as easy as saying "because there 4 vectors?"

He had a heart attack a month or so ago, and complications got him. You might remember him as the "gentle giant" in the film "The Green Mile". He played that part so well... RIP

1. Homework Statement [/b] Two smooth uniform spheres, A and B, are of the same size, but A has twice the mass of B. They are placed at rest on a smooth horizontal table and A is projected directly towards B with speed U. The spheres collide, and then B strikes a barrier perpendicular to its...

I recently bought a toy that has this magnetic disc riding on a metal rail. http://www.fizzicseducation.com.au/online%20store/large%20images/magnet%20rail%20twirler.gif After letting it gain momentum, I tilted it downwards and let it climb and fall (making U shape paths) and then come to...