Conceptual understanding Definition and 26 Threads

Hello All, I have a problem to understand this equation: $$ \dot{m}_{in} - \dot{m}_{out} = \frac{dm_{CV}}{dt} $$ It supposed to describe change in the mass of the control volume during a process. Two terms on the left are the total mass flow rates in and out of the system. I struggle to...

I'm trying to understand how optical holography works. I made a hologram using LitiHolo C_RT20 instant develop hologram film and am now trying to understand how this actually works. It almost makes sense to me. What I'm having trouble understanding, however, is this: Reference wave + object wave...

Homework Statement If two balls, being identical in volume, but different in density (one ball is made of iron, the other of aluminum) roll down from an inclined plane, which will reach the bottom first and which will cover a larger distance after having reached the bottom? IMPORTANT NOTE...

I'm a passout from school taking a gap year. I find the concept of conservation of momentum exceedingly difficult. Each question - and sometimes each part of a question, if a question has different parts - requires us to choose different systems each time. I look at the solution, and think I...

Hello all. After completing a problem in which we derived the formulas for potential and spring force energy as functions of time, with simple harmonic motion I noticed the equations are EXACTLY the same, but with sine and cosine switched. The equations were: A sin^2(pi * t) A cos^2(pi * t) I...

Homework Statement Homework EquationsThe Attempt at a Solution My difficulty is : If electron with orbital motion is taken as a dipole, then since the magnetic field is uniform, the net force due to magnetic field is 0. But, in eqn. 6.6, while calculating force acting on it , e is taken as a...

Homework Statement I saw this problem from a few years ago here on Physics Forum (https://www.physicsforums.com/threads/work-energy-theorem-problem.823990/) and wanted some clarification. Here is the problem: A curved plate of mass M is placed on the horizontal, frictionless plane as shown...

The more I think about it the less clear the respective natures of kinetic energy and potential energy (and of their sum, the so-called total energy) become. The thing is I have the impression that once you try to go a bit further than the usual description of "scalar values assigned to systems...

I'm having trouble understanding circuits, particularly voltage. So my question is more of a conceptual dilemma. Please correct my definitions and relations if it is incorrect. Voltage is the energy provided per charge, and this energy is converted to KE once the circuit is closed, or in other...

I have a few conceptual issues following a standard thought experiment to argue why light bends in a gravitational field and I'm hoping I can clear them up here. Consider an observer in a lift in free-fall in a uniform gravitational field and an observer at rest in the uniform gravitational...

I'm neither a physicist, nor working in a physics-related domain but I've tried for years to get interested in physics because of a fascination for questions like "what is the world" and "how does it works". I suppose this is a feeling shared by other people here. The thing is I have often...

Homework Statement Two identical twins, A & B, are riding identical bikes up the same hill, both at constant speed. Twin A takes 20 seconds to climb the hill, while twin B takes 40 seconds. a) Neglecting all forms of friction, which twin consumes more energy? b) With friction, which twin...

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...

Problem This is a conceptual problem from my self-study. I'm trying to learn the basics of group theory but this business of representations is a problem. I want to know how to interpret representations of a group in different dimensions. Relevant Example Take SO(3) for example; it's the...

NOTE: The following questions are not part of any homework assigned. This is part of finding extra concept-related questions to help me study for my physics unit test. Homework Statement I have conceptual questions, not problems. I'll provide sufficient evidence that I've attempted to think...

This is a two-part question: Firstly, as stated what was it that initially got you interested in physics. What was the part that ignited the fire of physics for you? Secondly, for me physics is a subject that I come back to every so often. Although, it seems to be increasing and more. My...

Hi, I am trying to wrap my head around what happens when a ball of mass m bounces against a hard floor. I assume a system that includes the ball and the floor (and eventually the entire planet) and an elastic collision. Before the ball hits the floor it has a momentum of mv. After the bounce...

Question:A bicyclist starts from home and rides back and forth along a straight East/West path. Her (instantaneous) velocity as a function of time is given by v(t), where time t is measured in minutes. Consider: d_{1} = \int^{30}_{0} v(t) dt and d_{2} = \int^{30}_{0} |v(t)| dt Choose what...

I've been able to do all the calculations and whatnot well in my physics class, but I recently stopped to think more about the concept of electricity and how it fundamentally works, but quite frankly I'm a bit stumped and there are some gaping holes in my understanding. Would someone please be...

More a question to some conceptual understanding of combinatorics. The number of ways of picking Na elements to be in a box A, Nb to be in a box B and Nc to be in box C is given by: N!/(Na!Nb!Nc!) One can proof this by saying: Suppose we start by putting Na in box A and so on. Now I have...

Hi, Originally I had a question about a wire that allows electrons to move to higher voltage. I could not figure out why the wire does not lose electrons to the point it runs out. The question was answered on these forums when someone mentioned salt bridges, which lead me to watch some video...

I would like to formally state that this is NOT a Homework question. I am NOT trying to cheat to get good marks. Instead the attached pdf file is a past examination question paper. Just take my word for it and I can do without the aggro of mods jumping on back. I would be EXTREMELY...

[PLAIN]http://img207.imageshack.us/img207/37/capturebg.jpg a=v^2/r v=2pir/T f=ma So I already have the answers to all the questions. The problem I am having is I don't understand why the centripetal force is not equal to the weight of the person. If it isn't the weight what...

Homework Statement A 1 kg object is moving along at speed of 5 m/s right before colliding with a 4 kg stationary object, in a perfectly inelastic collision. Suppose that the objects are moving on a surface that has a coefficient of friction of mu=0.2. (Note you may still assume that the...

concept problem There is a material and it is pulled by a distance by applying a force F. Tell me whether my intuitions is correct 1.In the world around we see materials of different shapes because the inter molecular forces bonds the molecules together in such shapes. 2.If one likes to...

The function y=0 is an equilibrium solution of the natural decay equation and the natural growth equation \frac{dy}{dt}=ky\\k>0. An equilibrium solution is stable if solutions that begin sufficiently close to the equilibrium soltuion tend toward that equilibrium solution as t\rightarrow\infty...