Conceptual Definition and 844 Threads

what does coordination no in crystal structures really mean? i know it's no of nearest neighbors but has it significantly to do with bonding of electrons. actually my doubt is that - I read Be can't show coordination no of 6 and is allowed to show only coordination no 4 due to lack of...

I am having trouble understanding the distribution of forces present within a pulley system; namely, how the number of sections of rope that supports an item manages to decrease the force necessary to move it. For example, look at this picture I am aware that system A only requires 5...

When a wire resists an electrical current it produces heat energy. But how efficient is this transfer? If the electrical Power is 20watts is the heating power 20watts? (ignoring all other inefficiencies, just the conversion from Electrical to Heat) I'm thinking since a circuit requires...

When a wire resists an electrical current it produces heat energy. But how efficient is this transfer? If the electrical Power is 20watts is the heating power 20watts? (ignoring all other inefficiencies, just the conversion from Electrical to Heat) I'm thinking since a circuit requires...

I'm taking a Calc III Course and I want to know if anyone out there can help me with a few conceptual ideas. I know how to do the math but I am missing the conceptual idea of it. Why should/do we we parametrize? Why should/do we convert to Polar or Cylindrical? These basic ideas should be...

3. A metal bar is hanging from a hook in the ceiling when it is suddenly struck by a ball that is moving horizontally (see figure). The ball is covered with glue, so it sticks to the bar. The collision takes place over a very short time span. During this collision a) the angular momentum of...

Homework Statement Consider a non conducting ring of radius r and mass m which has a total charge q distributed uniformly on it.The ring is rotated about its axis with an angular speed ω. a)Find the equivalent electric current in the circuit. b)Find the magnetic moment μ of the ring...

(1)If the limit of f(x), as x approaches a point a doesn't exist, and the limit of g(x), as x approaches a point a doesn't exist either, the limit of (f+g)(x) and (fxg)(x), as x approaches a point a can possibly exist? (2)If the limit of f(x) as x approaches a and the limit of (f+g)(x), as x...

Hello, My textbook says that if two equal masses, with the second one of them at rest initially, collide in an elastic collision. The first mass will stop and the second one will have the initial speed of the first mass. WHY? This makes no sense to me. Elastic collision only means momentum...

I'm looking at example 16.3 and 16.4 in Beer and Johnson vector mechanics dynamics. It seems that you can draw the forces in your FBD as "effective forces" on your KD (kinetic diagram). I'm confused about how I should choose to draw the effective forces at the centroid G or to draw them where...

Say for example I have a hollow cube with equal length/width on all sides. Let's also assume that the outside walls of this cube is unbreakable / perfect insulator / unable to deform in anyway. Now let's assume that we put a divider in the middle of the hollow cube of a certain thickness. The...

This could be one of those questions where I'm hindered by my lack of knowledge on the subject, being only a freshman in college, but recently we learned the uncertainty principle which states that: ΔE*Δt ≥ h/4π Given this, I'm assuming it'd be accurate to rewrite ΔE as Δm*c2, which would...

Homework Statement A system can be taken from state A to state B where SA = SB either by (a) directly along the adiabat S = constant, or (b) first along an isochore A to C and then along the isobar C to B. The difference in the work done by the system is simply the area enclosed between the...

Homework Statement The probability density at certain points for a particle in a box is zero. Does this imply that the particle cannot move across these points? Explain. (I found a picture online http://www.everyscience.com/Chemistry/Physical/Quantum_Mechanics/.images/PBxWvfns1.gif)...

Homework Statement Ok so had a lab where we used spherical mirrors and got the focal length and object distance etc by just using a meter stick mirror and light. Pretty common basic physics experiment(I think). But I was asked How to devise a method for using the lens to calculate the...

Homework Statement 16. Suppose P is the projection matrix onto the line through a. (a) Why is the inner product of x with Py equal to the inner product of Px with y? (b) Are the two angles the same? Find their cosines if a = (1;1;¡1), x = (2;0;1), y = (2;1;2). (c) Why is the inner...

Hello, PF! [My question pertains to a non-rigorous, undergraduate introductory Probability and Statistics course. I'm no math major, so please correct me if I've mishandled any terms or concepts as I try to express myself. I'm always eager to learn!] * * * In a discussion of the...

Conceptual question help--Electric fields, potentials, etc. Homework Statement 1) Assume that the electric field E is equal to zero at a given point. Does it mean the electric potential V must also be equal to zero at this point? If not, provide an example to prove your answer. if you think...

Homework Statement I'm interested in an explanation of the forces/principles involved in the following scenario: There are two syringes, level with one another, containing the same volume of water. The difference between the syringes is the gauge of the needle; one is of greater diameter...

Newton's Third Law states that for every action force, there is a reaction force. So take a classical problem with a basketball player. The Earth has a gravitational force on the player, and thus player exerts an equal and opposite force on the earth. The player is stationary. My first...

Homework Statement Assume we have two neutral plates a small distance away from each other. We place charge Q on one plate, leaving the other plate uncharged. We then measure a potential difference V across the plates. Some bright student notes the ratio of Q and V is not the value of the...

Hi, Im new to PF and Physics so pardon my likely extremely basic question (teaching myself physics). 1.) Question: (a) an empty sled is sliding on frictionless ice when susan drops vertically from a tree above onto the sled. When she lands, does the sled speed up, slow down, or keep the same...

Apologies if this seems a bit trivial, but I was hoping to clear up a bit of confusion that I'm having. First Question: When considering an N-particle quantum system, described by some wave-function, \Psi\left(\vec{r}_{1},\ldots,\vec{r}_{N}\right). Is it correct to consider each particle to...

Hey Dear forum, I know I'm wrong, but I don't know why: Since the Earth's descends 5 meters for every 8km, a horizontal speed of 8km/sec will put an object to rotate around the Earth (neglecting air resistance). I.e. in one second it will fall 5m below it's initial height, but so will the...

Homework Statement I have some conceptual question in the fluid mechanics topics which has been bugging me for quite some time now. 1) When wax is rubbed on cloth why does the cloth become waterproof 2) A weightless baloon is filled with water. What will be the apparent weight when...

Homework Statement Both Q1 = Q2 = +5E-6 and are harnessed to screen and in a vacuum.----Q1---A----Q2------B--------P this is x axis, A and B are distances Homework Equations kQ/r^2 The Attempt at a Solution So the E field at point P is KQ1/(A+B)^2 + KQ2/(B)^2 My question is Why...

Homework Statement 1. When the following reaction proceeds, what will be true? 2A(g) + 3B(g) -> 4C(g) (1) The temperature will increase at constant P and V. (2) The volume will increase at constant T and P. (3) The pressure will increase at constant T and V. (4) The density will...

Homework Statement I am having a little trouble using mesh analysis. I'm trying to stick rigorously to the passive sign convention, as I'm told that this is sensible. Consider the circuit diagram attached, where I have added the mesh currents in orange. In red are the polarities for the...

Homework Statement A spool of wire rests on a horizontal surface as in Figure P10.87. As the wire is pulled, the spool does not slip at the contact point P. On separate trials, each one of the forces F1, F2, F3, and F4 is applied to the spool. For each one of these forces, determine the...

So, we are learning about simultaneous rotational and translational motion. I understand that they can be dealt with independently -- for example, if 2 identical rods have a force applied to them at different points, their rotational motion will differ but they will both have the same...

Homework Statement Why does the Van der Waals equation adjust pressure up and volume down? Homework Equations (P + a)(V-b) = nRT (overly simplified, but it gets the point across). The Attempt at a Solution Okay. Volume refers to total free volume in a container in the context...

General relativity -- Conceptual question Hello, I have a conceptual question. May be I am sounding a little bit idiotic, so apologize for that. I believe, there is no harming in knowing that I am wrong. Einstein's general theory of relativity describes gravity as a geometry of space...

~~Conceptual Normal Force Question~~ Hello! Suppose there is a meter stick suspended from and parallel to a table. On one end, the meter stick is held up by a piece of string at an angle. On the other end, the meter stick is held up by a metal thing about 10cm tall, simply allowing the stick...

Hey all, in physics right now I am learning about rigid body rotations about a fixed axis. One of the questions we had for homework goes like this: "The combination of a friction force and applied force produces a constant total torque of 36 N*m on a wheel rotating about a fixed axis. The...

How can, for example, M_2(R) have four dimensions? What I mean is how can a 2x2 matrix be considered a vector? Also how can the set of solutions to a linear differential equation be a set of vectors? Or are these examples supposed to be the idea of vector spaces applied outside the realm of...

I've read that there's a point in a black hole where matter is infinitely dense. There is zero volume but infinite density. How is it possible for something to have zero volume but have an infinite density at the same time?

Starting with this equation, E^2 = p^2c^2 + m^2c^4 With a photon, m = 0... what happens when E starts to get large? Very large. As E approaches infinity, do strange things happen? Will a singularity form? If we let our photon have a mass, something very small, will the picture change at...

Homework Statement Hi guys, so I'm struggling with understanding the heaviside function clearly. In particular, I am struggling to understand how changing f(t) to f(t-3) ''shifts'' everything to the right. Homework Equations Say we take the following heaviside function f(t-3) = 7...

"Easy" conceptual energy problem? Homework Statement Here's the diagram http://nkkkjkjjjjjjjjjjj.tumblr.com/image/65137695911 A bead slides on a wire, which is in a vertical plane, as shown in the diagram. Gravity acts in the -y direction. The bead starts at A, moving to the right with an...

Homework Statement I am having a few doubts while writing relationship between angular speed and linear speed ,in the reference frame of a moving observer . Suppose at an instant, car A is heading towards car B with velocity 'v'. Car B is moving towards right with velocity 'u' ,i.e along...

Homework Statement If two objects are moving towards each other with two different velocities and two different mass then crash and stick together, find the force acted upon each object during the collision if the collision occurred over some time "t" Homework Equations m1v1+m2v2 =...

If we have charge in an isolated conductor, is there any way to get it off without physical contact or arcing?

Homework Statement 1). Magnetic Field lines begin and end at magnetic charges. (True or False) 2). Magnetic field lines are "lines of force" for charged particles. (For example, a charge will follow the magnetic field lines.) Homework Equations The Attempt at a Solution I...

Suppose there are two spheres freely floating on the surface of an infinitely large and deep body of water. Suppose these two spheres bob up and down independently and create waves (which may or may not have the same frequency and amplitude) in the water. Do these spheres always remain...

Not homework per se, but this is giving me so much problems in their resolution: long story short, dealing with the 1st Principle, which would be the proper way to note down energetic exchanges in a closed system? I'm coming here from handling hydraulic systems with springs attached, and one or...

I am having some conceptual trouble in my physics II class right now. The book is not that good, and I am looking for a website that has good conceptual practice. Do any of you know a website like this? My professors conceptual quizzes are killing me right now, and it would be much appreciated.

Homework Statement Consider a fluid between two plates. One on the bottom which is stationary, and one at the top which is moving at constant velocity V. The plates are separated by distance h. Does shear stress change as you move further from the moving plate? Homework Equations the...

Hi all, I've started the course of Physics at college last year and I need some advice right now. My main areas of interest are General Relativity and Quantum Mechanics, and these theories as well as every math needed to understand them wouldn't be covered in the course in detail (General...

Homework Statement a block of mass m = 1.62kg slides down a frictionless incline.the block is raised a height h = 3.91m above the bottom of theloop. (a) what is the force of the inclined track on the block atthe bottom (point A)? (b) what is the force of the track on the block at pointB...

Hi guys, This is a basic circuit that you'd commonly see in a flash Camera. Hambley says (roughly paraphrased): When the electronic switch is toggled rapidly (1000s of times a second) the inductor charges due to a change in current. v=L(di/dt). The diode allows current to flow into the...