Conceptual Definition and 874 Threads

This conceptual question really got me thinking but I'm not sure how I would explain it: Your friend has been studying physics. She tells you that because of Newton's Third Law, she exerts a force on the Earth opposite to the force that it exerts on her. this worries her a lot because she...

I am looking for books that introduce the fundamentals of topology or manifolds. Not looking for proofs and rigor. Something that steps through fundamental theorems in the field, but gives conceptual explanations.

Can anyone comment on this book?

Homework Statement Determine the failure mechanism and plastic moment for the following structure, using either the upper bound or lower bound theorem for plastic analysis. Picture (There is a physical hinge in the middle of the structure) Homework Equations Internal Work = External Work...

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, I have just begun a self-study program in analysis and have a question about Dedekind cuts. My question is this: My understanding is that cuts are constructions by which to define the reals in terms of the rationals. I.e. the reals are a set of cuts, each of which is a set of...

Homework Statement Even for an ideal transformer, we can't get "something for nothing". If this transformer steps up the voltage, what must be decreased? a) power b) current c) resistance The Attempt at a Solution Ep/Np=Es/Ns I believe it's power or current, but these two are related. So...

Homework Statement A magnetic field is uniform throughout a region of space, but increases from 0 to 0.14 T in 2.4 s. A circular coil (of diameter 19 cm) is placed in a fixed orientation in this region such as to receive maximum flux. It takes 4171.91 turns to generate an emf of 6.9 V What...

Say that I have two objects of the same mass and volume. I place one into freshwater and another in glycerine. In both cases, the objects are floating. Would the buoyant force from both of these fluids acting on the object be the same? From my understanding, buoyant force measures the weight...

Hello, I got into a very little and simple problem which I should understand. But I don't.. Look at this picture: The mass naturally will move downwards from the hill. Oke, no problem. Analysing the external forces applied to this mass: gravity and friction. Gravity, independent of...

If an object was thrown horizontally over a cliff, would you expect it to take longer ot hit the ground below than if it was just dropped over? Please explain. Many thanks.

Homework Statement Hello, i encounter a conceptual probability problem that I think i have come into confusio. The situation is - There are 3 Blue ball and 1 Red ball in a bag (BBBR), while there are 4 Green balls in another bag (GGGG) If one of the balls is taken from bag A to bag B...

Homework Statement http://img207.imageshack.us/img207/3756/24134024.jpg N.B: (0+) means just after switch is open, and (0-) means just before switch is open. I have the solutions for this, but there are some problems I have with understanding how inductors and capacitors work in...

It is well known that, "Neil bohr failed in his model in which he described an electron as a charged particle moving in well defined circular orbits about the nucleus." However he failed because of the two major reasons.. a) It didn't consider the wave nature of the electrons b) contradicts the...

If there is a parallel plate capacitor, connected to a battery, which is then disconnected, there is NO voltage now, but "Q" (charge) on the capacitor remains the same. YES OR NO? I think yes.

For three vectors to add up to zero, what must be true of the magnitudes of the three vectors? Hint: Draw a diagram of the addition of three vectors to make a vector of zero length. Think of what geometrical relationship they must have. a. All the magnitudes must be equal. b. One of the...

I drive 45 mins one way to class 5 days a week and started thinking maybe it wouldn't be so miserable if I had something interesting to listen to instead of the same music over and over. I'm a mech engineering undergrad with an aerospace concentration, at I'd guess the sophomore level. Not...

So anytime I've seen textbooks explain integrated rate laws, they usually start with a reaction of the form A -> B and then from there say, if we know the reaction is first order with respect to [A] then: v = -d[A]/dt = k[A] And then subsequently integrate this to find ln[A]/[A]i = -kt...

Homework Statement The figure shows a wire that is connected to a power supply and suspended between the poles of a magnet. When the switch is closed, the wire deflects in the direction shown. Which of the dashed boxes A–D represents the position of the north magnetic pole? Homework...

Homework Statement Two bodies "P" and "Q" are on a frictionless horizontal surface are connected by a light cord. The mass of "P" is greater than that of "Q." A horizontal force "F" is applied to "Q" as shown below, acceleration the bodies to the right. The magnitude of the force "F" exerted...

So this isn't a homework problem persay, it was given information but I just couldn't wrap my head on why this was true. We have 1-d heat transfer through a planar slab. If we have a T_a for the temperature outside, then as we T_1 for the temperature on one end of the surface, and T_2 for the...

Homework Statement So my question is conceptual. I am trying to figure out in what direction an electron will move if it starts between two plates of a parallel plate capacitator. One of the plates is at 0V and the other is at 50V. Also, would placing a dielectric in a charged, isolated...

Homework Statement This is a question I once encountered with a window advertisement popup, but I think I can work out the answer but I don't know how to logically explain it to my kids. 10 people can paint 60 houses in 120 days. How many houses can 5 people paint in 60 days Homework...

Homework Statement There are two paths up a hill, a steep one and a less steep one. If we travel at the same speed along the paths, what can we say about your power in climbing the hill? A) more on the steep one B) more on the less steep one C) the same on each D) it depends on...

Homework Statement Suppose L1 and L2 are skew lines. Is it possible for a non-zero vector to be perpendicular to both L1 and L2? Give reasons for your answers. Homework Equations I know that skew lines are not parallel or intersect. Also, they don't lie on the same plane. The Attempt...

Just curious, how does one switch from the frequency version of a Fourier transform to the ω version. I know that ω = 2∏*f but looking at the variations of the table it seems like there is more than just this difference

Homework Statement So the outside of a refrigerator is made up of plastic, metal, and insulation? Which is the most important and why. Homework Equations no equation needed. The Attempt at a Solution I thought that the insulation would be the most important because it reduces...

Homework Statement Answer the following with regard to the current loop shown in the figure. http://i.imgur.com/Lkp4D.gif TRUE OR FALSE: The B Field at C points into the plane of the paper. If an external magnetic field directed out of the plane of the paper were introduced, the torque on...

Homework Statement A very strong magnet is suspended by a non-magnetic thread. A student forms a loop out of a wire attached to the Pasco 750 Interface as shown on the left. During a half second interval, the student moves the wire loop until it is below the magnet as show a) Describe...

Homework Statement I have a nonhomogeneous 2nd order DE and I am given one solution to it and told to use variation of parameters? to get the general solution. First i need to get the 2nd solution though. Should I use reduction of order to get the 2nd solution? If so, then in what form should...

Two pucks collide on a frictionless air-hockey table. Initally, puck A is traveling at 3.5 mls and puck B is at rest. After the collision, puck A moves away at a speed of 2.5 m/s and an angle of 30.0 from the initial direction. Find the final velocity of puck B. Puck A has a mass of 3.0 kg and...

Homework Statement Answer the following questions for a mass that is hanging on a spring and oscillating up and down with simple harmonic motion. Note: the oscillation is small enough that the spring stays stretched beyond its rest length the entire time. Answers available: Top, Equilibrium...

1) An Ohmic device is one that obeys Ohm’s Law. According to your data, are carbon resistors Ohmic devices? Support your answer with references to your graphs and/or equations. 2) When a typical circuit is switched on, the net displacement of electrons along a wire is about 1 mm per second. If...

Homework Statement Two objects of equal mass are on a turning wheel. Mass 1 is located at the rim of the wheel while mass 2 is located halfway between the rim and the axis of rotation. The wheel is rotating with a non-zero angular acceleration. For each of the following statements select the...

I have (conceptual) questions about this question posted before: https://www.physicsforums.com/showthread.php?t=386071 On the second part of the question (part B: The switch is opened at t = 0s. At what time has the charge on the capacitor decreased to 12% of its initial value?), why does...

EDIT: Ooops, the title says sphere, but it is a cylinder. I cannot edit the title... sorry... I saw this problem in a book and it is really bugging me. It is not a homework problem, I have the fully worked out solution in the book. I just have a conceptual problem. Given a hollow cylinder...

Homework Statement You have a horizontal spring system such that it undergoes SHO on a frictionless surface. with a known mass attached at the end of the spring. When that mass reaches its maximum position (amplitude) a second identical mass is dropped on top of the initial, effectively...

Hello Physicists, I don't have an actual math problem, just a conceptual one. I was wondering specifically about light resonance. If I understand resonance correctly, if one has two mirrors directly facing each other, one can create a standing wave. At a certain frequency of the light...

Homework Statement An astronaut is taking a space walk near the shuttle when her safety tether breaks. What should the astronaut do to get back to the shuttle? Attempt to "swim" toward the shuttle. Take slow steps toward the shuttle. Take a tool from her tool belt and throw it away...

Homework Statement My questions are as follows: (1) If I apply a force (B) on a beam with a center of gravity at the middle(A), it will JUST cause a moment, correct? (2) If I remove this fixed point(A), and no gravity or any other forces are present, will it still JUST cause a moment or will...

Homework Statement A thought experiment. Imagine ants living on a merry-goround, which is their two-dimensional world. From measurements on small circles they are thoroughly familiar with the number pi. When they measure the circumference of their world, and divide it by the diameter, they...

It is neither a homework nor coursework problem, but I really want to know the solution. Homework Statement 3 charged capacitors are connected as shown in the diagram. What will be their final charges, potential difference when equilibrium is reached? Units are arbitrary...

Plz help me out with this difficulty. Here is a figure showing two conducting spheres(haven't drawn all EF lines):- Here is the problem, Suppose one of the spheres is charged with a charge +Q, other is neutral , so charges will get induced as shown in figure. The left portion of orange...

Homework Statement Do objects same kinetic energy in all inertial reference frames? For objects interacting, is energy conserved in all inertial reference frames? Homework Equations None The Attempt at a Solution I think the answers are No for the first one, and Yes for the...

Homework Statement If speed, v, of an object depends on time, t, according to the equation v = A + Bt + Ct^4, what are the SI units of A, B, C? Homework Equations v = A + Bt + Ct^4 The Attempt at a Solution For this, I've not known where to start, so I've be plugging in the variables...

Thank you in advance for reading this and hopefully answering my questions. I've spent about two hours or so now trying to get my questions organized in a clear way, so that they are direct and to the point. I've drawn an image to help explain what I'm getting at. I'm not much of an artist...

Hi everybody, Currently, I am studying cohomology on my own. I have a question: Why H rD(M) = 0, when r > n n is the dimension of manifold M My book says it is obvious, but to me it is not obvious. I wish someone could explain this question to me.

Suppose we could isolate a single proton and a single electron, and have them near each other without the high kinetic energies like in particle colliders. imagine holding them in a perfect vacuum without gravity, a mm or so apart lol. Then we let them go. What would they do? They're...

I'm willing to say that I have a fair understanding of Electromagnetism, at least from a classical perspective, but I was never entirely clear about the difference between, say, the time-varying magnetic field created by an inductor and the Electromagnetic field of light in general. Based on...

Homework Statement A 30-ft-high, 1-ft-diameter pipe is welded to the top of a cubic container (3ft x 3ft x 3ft). The container and pipe are filled with water at 20°C. Determine the pressure forces on the bottom and sides of the container. I already know the solution to this problem, but I...