Conceptual Definition and 844 Threads

Hi! I'm new to the forums, so I apologize in advance if I'm posting my question in the wrong section. I'm studying thermodynamics right now, and I came across this sentence from my book: Homework Statement "When energy is added to a system and there is no change in the kinetic or potential...

explain the question by example; I hit a piece of wood with a mallet and record a pulse ie; zooming in I get a specific frequency; pretend it is a sine wave of frequency 500HzI then beat the wood with a frequency of 10 000Hz (pretend this is a 10 000HZ sine wave beating; so what is the...

I saw this problem in my dynamics class: http://d2vlcm61l7u1fs.cloudfront.net/media%2Fa22%2Fa2261e7a-0e85-45e7-8b63-f23157d623bc%2Fphp37ql1a.png I know how to solve it, but I don't understand why A(bd) has both a normal and tangential component to acceleration. If it is rotating at a constant...

You know the proofs for finding the apparent depth of a swimming pool, or object submerged in one? Well, it always assumes the object is directly above the original object. Does anyone know where the assumption comes from? (see below)

Homework Statement When an aluminum ring is placed on ring launcher so that it surrounds the coil, it flies upward when a AC current is applied to the coil. This does not occur when the intact ring is replaced by a split ring (see below). Explain this in 3 sentences or less. Feel free to use as...

Hi PF, I've got a very trivial conceptual question regarding the conservation of energy with respect to thermodynamics and heat transfer that I can't seem to figure out. Suppose I have an electric heating element with a 240 volt, 30 amp supply, in contact with a solid volume of an arbitrary...

You have a capacitor and each plate is of area A, explain qualitatively what happens to the capacitance when you increase the size of only one of the plates and why. Edit: adding some conditions: 1. they are circular discs (for simplicity's sake) 2. one has diameter d1, one has d2, 3. make...

Hi I'm just having trouble wrapping my head around differential equations with matrices and vectors... For example: let y be a vector. let A(t) be an nxn matrix. I have the differential equation: dy/dt = A(t)y So I think I understand why the solution is y = ceA(t) But I'm having trouble...

Homework Statement Rods of negligible mass connect discrete masses as shown in the diagram below. For each system, the masses rotate about the midpoint of each connecting rod. Furthermore the systems appear to rotate in unison as time progresses. Do the systems have the same velocity? Homework...

Homework Statement A 60.0 kg woman stands at the western rim of a horizontal turntable having a moment of inertia of 500 and radius 0f 2.00 m. Turntable is initially at rest and is free to rotate around frictionless vertical axle through its center. Woman then starts walking around the rim at...

Homework Statement Homework Equations The Attempt at a Solution 1) I think the answer is c) . Since initially there is no pressure above water , it starts vaporizing . This causes loss of thermal energy from water . The heat lost results in water freezing .The process continues till all the...

I'm trying to read up on some traffic flow models and I've encountered the following equation (source [pdf]): Variables are ##t =## time, ##x =## space variable along road, ##\rho (t, x) =## density of cars, ##v(\rho ) =## velocity, ##Q = \rho \times v## Following graphic is used to show...

So understand how to solve a problem using the equation: ΔS=Q/T But is there a conceptual explanation for why the equation works. And I'm not looking for a proof, but I simply want to understand why this equation should be intuitive. Thanks for your time!

So I understand that enthalpy is energy. But what energy specifically? Is enthalpy heat energy? Is it the energy that bonds atoms together and that's why it can either be released or absorbed? Or is that what Gibbs free energy is? I'm trying to make sense of the equation: ΔG=ΔH-TΔS...

1. Question: Ball A of mass ma is traveling along the x-axis with velocity vao when it strikes Ball B of mass mb, which is at rest. After the collision, Ball A travels at an angle θ above the x-axis and Ball B travels at an angle φ below the x-axis. The final velocities of Balls A and B are vaf...

Homework Statement If a roller coaster car enters the circular-loop portion of the ride and navigates it successfully, then the net force on the car at its topmost point is straight down. Then why does not the car fall down? So I am having issues understanding my textbook's solution to the...

Hello everyone! I've been studying the Special Theory of Relativity for a little while on my own, and I've had some difficulty understanding exactly what it is saying about the character of time. I would guess that these are very similar to the sorts of conceptual difficulties that a lot of...

I know that this question has been asked many times before on this forum, but on every existing thread either the question or the answers, or both, were too vague. I understand that inertial mass is defined as the property of an object to resist change of its velocity, that is the mass that...

Homework Statement I took a stab at the following question in a book: "In one observation, the column in a mercury barometer has a measured height h of 740.35 mm.The tem- perature is -5.0 C, at which temperature the density of mercury r is 1.3608 10^4 kg/m^3 .The free-fall acceleration g at...

From a physical perspective, is the reason why one requires that the norm of a state vector (of an isolated quantum system) is conserved under time evolution to do with the fact that the state vector contains all information about the state of the system at each given time (i.e. the...

Homework Statement . First problem - [/B]Homework Equations F=Ma The Attempt at a Solution Thinking in terms of Newton's second law ,since there is no external force on the system(fan+sail+boat) ,the boat should not move . Thinking in terms of Newton's third law ,the fan pushes on the air...

Homework Statement I'm having a little trouble knowing when to use the ideal gas equations for entropy vs just the ones like this: (T2/T1)=(p2/p1)^((k-1)/k). I've noticed a pattern in the solutions for my homework( where you're finding isentropic efficiency of turbines and compressors) they...

Homework Statement Even conceptual problem in the text: Consider a standard RLC circuit driven by an AC source in which the elements are in parallel. Construct a phasor diagram and develop an expression for the phase angle θ. Now remove the resistor from the circuit, can you still develop an...

Just curious, explanation if youre going to answer please! 2 horizontal disks stacked on one another spinning at constant v, (about a frictionless axis perpendicular to their center), both have mass. Okay, so let's say its possible to instantaneously remove the top disk. So would that make...

I'm looking for suggestions of resources to learn introductory E&M and "modern physics" (I'm thinking relativity, QM, particle) conceptually. This learning is out of self interest. While my focus is for conceptual understanding, this doesn't mean any suggested resources should be devoid of...

Homework Statement Does a purely rotating body (something like a disk hinged at a point and rotating with some angular speed) have zero linear momentum? Homework EquationsThe Attempt at a Solution I believe it will, but I'm not like completely convinced. I tried to draw an analogy with a...

Homework Statement Question says there is a car moving at 2 m/s and a projectile is launched from top of the car at a speed of 7 m/s relative to the car. They give the angle as 25 degrees above the horizontal but then ask what is the angle that it makes with ground when it finally lands? My...

Homework Statement I am reading a note on differential equation.There is a point that I don't understand,hopefully someone can explain (Please see the attched) Homework EquationsThe Attempt at a Solution The notes wrote " a1t + b1 x + c1 = a1T + b1X a2t + b2t + c2...

Hi I'm having a few conceptual difficulties with random variables and I was hoping someone could clear up a few things for me: 1) Firstly, what exactly do we mean when we say that two random variables X and Y are equal. I understand what identically distributed means, but my difficulty is with...

In Griffiths, it seems that the conceptual introduction of the magnetic vector potential to electrodynamics was justified based on the fact that the divergence of a curl is zero; so we can define a magnetic field as the curl of another vector A and still maintain consistency with Maxwell's...

Homework Statement Can someone give me an explanation of a polytropic process and maybe an example? I know it obeys pvn=constant, but I can't seem to find a definition that makes this concept click in my head. Would you consider isobaric, isothermal, and isochoric processes to be polytropic...

It appears that I will be assigned to teach a modern physics course centered on quantum mechanics for those with almost no math background and I am searching for a suitable book. Essentially, this would be the modern physics equivalent of Paul Hewitt's Conceptual Physics book. I thought of...

Hello all, I was wondering, what is a really great introductory general chemistry book/source (covers chemical kinetics, thermodynamics, electronic structure, electrochemistry, acid-base equilibria, etc.) that has a lot of conceptual questions and not just quantitative? An example is like...

Edit: sorry i realized i posted this in the wrong section. Can some move it to hw? Thank you. Hey i was s[SIZE=16px]tudying intro E&M recently and i started learning about RC circuits. Up until this point everything, concept wise, has made sense for me. Then I learned how RC circuits work, and...

Physics forum users, Thanks in advance for your help and discussion! I am looking for conceptual problems in introductory physics which include solutions -- for self study. It should cover all the material for the IIT or GRE exams, but should emphasize forming connections, analysis and applying...

This is mostly a conceptual confusion I'm having, not a specific problem, so it didn't seem like it'd fit under homework problems. I'm having trouble understanding when potential energy should or shouldn't be used in a energy conservation equation. When looking at a problem with a skier going...

Homework Statement Say, for example, a wave function is defined as 1/sqrt(2)[ψ(1)+ψ(2)] where ψ are the normalized stationary state energy eigenfunctions of the ISQ. Now, say I make a measurement of position. What becomes of the wavefunction at a time t>0 after the position measurement (i.e...

Homework Statement A uniform rod of mass 3.15×10−2kg and length 0.380m rotates in a horizontal plane about a fixed axis through its center and perpendicular to the rod. Two small rings, each with mass 0.250kg , are mounted so that they can slide along the rod. They are initially held by catches...

Homework Statement Today we were studying a block on an incline and determining the angle needed for the block to start sliding. The question asked is: Why is the equation for the coefficient of static friction independent of the weight of the block? Homework Equations ΣFx=Fapplied-fs=0...

So I have one last roadblock to understanding how circuits fully work and it has to do with currents (in series). To my current understanding, if we were to have a simple DC circuit with one battery at 10V and one resistor at 10 ohms, the current at all points in the wire is 1 A. Now, if we were...

haruspex submitted a new PF Insights post Conceptual Difficulties in the Roles of Variables Continue reading the Original PF Insights Post.

Homework Statement This isn't a homework problem, but I was just thinking of the following question: Suppose that a merry go round spins with a constant speed (so its radially accelerating towards the center), and a man want to jump onto the merry go-round while its spinning. In what way...

Homework Statement A lens has a radius of curvature of magnitude R on its left surface and a radius of curvature of magnitude 2R on its right surface. Parallel rays entering the lens from the left are focused to a point 135mm to the right of the right surface. At what distance from the lens is...

Homework Statement The general wave equation can be shown as: y(x,t) = ymsin(kx-ωt) Homework Equations See above The Attempt at a Solution My question relates to the variables present in this equation. I understand what the amplitude is, its the magnitude of the maximum displacement of...

A sphere (with density less than that of water) is placed into 2 different cylinders. One with a spinning column of water and the other with a still column of water. Why does the sphere in the spinning column of water take much longer to float to the top of the cylinder? I was thinking about...

Hello, I bought conceptual physics 9th edition by Paul Hewitt. A teach recommended it to me to study conceptual physics/conceptual physics GRE problems. I can't find a teacher's manual or answer key though. It seems pointless to work though problems without it. Does anyone know if this exists or...

Homework Statement This is a conceptual question about a prior assignment I had: A thin spherical shell rolls down an incline without slipping. If the linear acceleration of the center of mass of the shell is 0.23g, what is the angle the incline makes with the horizontal? Homework Equations...

Homework Statement There's a conceptual question I've encountered in my reading, wherein we're supposed to determine the validity of a statement: "According to Pascal’s principle, if you increase the pressure enough so that the force at one end of an oil-filled tube increases by 10 N, the force...

Homework Statement To rephrase the question, given a power series representation for a function, like ex , and its MacLaurin Series, when I expand the two there's no difference between the two, but my question is: Is this true for all functions? Or does the Radius of Convergence have to do with...

Homework Statement Three building materials, plasterboard [k = 0.30 J/(s m Co)], brick [k = 0.60 J/(s m Co)], and wood [k = 0.10 J/(s m Co)], are sandwiched together (as I've tried to show below). The temperatures at the inside and outside surfaces are 28.9°C and 0°C, respectively. Each...