Confusion Definition and 1000 Threads

If there is always an equal an opposite reaction, wouldn't everything always be in equilibrium and there'd be no net forces? If a car's exhaust is pushing back with xN, the car gets pushed forwards with xN. So the net force is 0 so how can there be acceleration?

Okay So, the question I have here is.. Masses are connected as shown. m1 = 5.0 kg and m2 = 4.0 kg. a) find the acceleration of each object and b) the tension in the two strings I have attached the picture example as well (as there is another unlisted weight in it) With pulley problem's I...

I just have one quick question on using direct calorimeters on humans, and it might be a dumb question but its got me a bit confused. From my understanding the calorimeter will measure the change in temperature of water from the heat that a person's body gives off. I understand that when...

Hi all, First off, not sure which forum maybe the most relevent, hopefully this one is the most suited? I do not have much of a background in maths, so bare with me. I am trying to implement a Modular exponentiation encryption method, I am using...

I curiously never had a problem solving Seperable Equations in the Seperable Equations chapter of the Boyce/Diprima book. I am the kind of person who likes to do things the long way, and encountered a problem solving for an Integrating Factor(Linear ODE, NOT EXACT) the long proofy way. I tend...

I had a problem a few days ago that involved a yo-yo falling. It was a disk with a string wrapped around it, and the string was attached at a certain height. In the explanation for the problem, it said the equation "weight - tension = ma" could be used to find the linear acceleration of the...

Homework Statement See first figure attached. Homework Equations The Attempt at a Solution For this question I understand parts 1) and 2) entirely and have obtained the correct answers from the solutions. I am confused about part 3) and I think my confusion stems out from...

Hi Recently performed a very basic fluid mechanics experiment with water flowing at different speeds through a Venturi Rig. Most of it went as expected, total head stayed roughly the same throughout but slightly decreased from flow loss due to resistant forces. However, at certain random...

Homework Statement Let's say an object is moving with x(t)= e^(-1/t^2) it's motion is continuous everywhere and differentiable because its exponential so v(t)= 2e^(-1/t^2)/t^3 a(t)= e^(-1/t^2) *(4-6t^2)/t^6 I have asked to a calculus teacher and he said all the derivatives will be 0 at...

Homework Statement See figure attached. Homework Equations The Attempt at a Solution If we attempt to solve part a) in this question we encounter several confusions. If we assume i(t) to be a positive current, the magnetic flux will flow through the core in a counter...

Homework Statement In a constant pressure process ant 1 bar determine how much heat must be added to raise the temperature of 2kg of compressed water at a temp of 50C so that it become superheated steam at a temp of 200C? u2=2659KJ/Kg Homework Equations W=-P(V2-V1) Q+W=U2-U1 The...

My physics book explains a van de Graaff in this way: A small conducting sphere of radius a and carrying charge q is located inside a larger shell of radius b that carries charge Q. A conducting path is momentarily established between the two conductors, and the charge q then moves entirely to...

I was reading in my chemistry book about significant numbers. Also about measured and exact numbers. From what I understand, a measured quantity can be different than an exact number. The book said when comparing something, like 1 lb = 16 oz, it is an exact number because the two are the same...

Higgs Confusion (The Higgs "Era") I thought I understood the basic concepts behind the Higgs mechanism (spontaneous symmetry breaking and such). But I've read a couple of sources that talk about the "Higgs Era" - the period shortly after the BB when the U was still hot/dense enough for the...

Homework Statement I am currently doing some Hooke's Law problems. While I do not have any trouble with any exercise in particular, I do have trouble with the sign in the equation. Let's say I have a vertical spring and I attached a hanging mass m to it. The string will then stretch a distance...

My professor introduced to us this concept, but when she was explaining it, I don't think she even knows what she is talking about. So I've come to ask people who know their stuff to help. I was told that on R2, the inequalities (1) x > 0, y > 0 Is open and unbounded (2) x \geq...

this example was in a book I bought ( maths methods for physics, Mathews and Walker) dy/dx + sqrt( (1-y^2) / (1-x^2) ) = 0 dy/(1-y^2) + dx/(1-x^2) = 0 sin -1 y + sin -1 x = c [1] or, taking the sine of both sides x (1-y^2)^1/2 + y...

Hi all, Just having some trouble understanding a certain example of cross product. It's actually for physics, but figured it belongs in this forum. In the question I am supposed to cross (dl)y hat with (x1)x hat. So I go (0 dl 0) x (x1 0 0) = (-x1dl)z hat. But turns out the answer the...

Homework Statement So basically I have plotted two variables I measured on a graph, which gives a simple linear relationship, and have found the gradient and standard error of the gradient (1.21251 and 0.03275 respectively). Now my problem is that this gradient is equal to a constant divided...

I attached the drawing. The problem state ment is to find the magnetic field at point P. the straight line segments cause no field. I have no problems with getting the numbers for this problem but I am confused about the direction. The solution manual says the field is out of the page, I don't...

Okay, so we did a lab in class with Na2CO3 in BaCl2 first. The reaction formed a white precipitate, and I suppose the products are BaCO3 + 2NaCl. Not sure if NaCl is dissolved or not, or if it was the white precipitate I saw, but anyways, here's my question... We added HNO3 to that new...

A statement in a book of analysis I have says: (Q,+, .) is a commutative ring with an identity element. I assume by its notation (Q,+,.) is a tuple.(correct?) There are several questions that come to mind: 1. Why is there an order between Q,+ and . ? 2. As far as I know, a tuple is an...

im a bit confused - please help - I am a complete beginner! I have several classes, within which are several attributes defined and declared. The assocation between some of these classes are aggregation, and between others is compostion. Take the example of person and car being and...

Hello Everyone! I have recently been attempting to understand negative resistance circuits(on a practical level at least to start). I've pulled up a few websites giving actual circuits to demonstrate the principle, but still can't quite understand it. Every circuit example so far shows either...

This is a really dumb question, but could someone quickly explain why it is that if b > a in the equation of an ellipse then y is the major axis. Just intuitively I want to think that y^2/5 as opposed to y^2/3 is going to be smaller for a given value of y since each value is being limited by...

Homework Statement Is is possible to have capacitor with one plate charge +Q and another charge -K, K≠Q. Homework Equations C=Q/ΔV. Because i wouldn't know what to substitute for Q.. The Attempt at a Solution I don't think it is possible for a capacitor connected to a single...

Homework Statement I am trying to understand the concept of short circuit with kvl laws it seems like i arrive at contradictory stuff http://imageshack.us/photo/my-images/38/shortcircuitr.png/ it seems like the voltage across the wire and resistor are equal by KVL however the current...

I'm currently in an introductory thermal physics course, and today we learned about the Boltzmann factor and how to use it to calculate various quantities with the corresponding probability distribution. All was going well until we got to the subject of paramagnetism. We supposed a system of...

I am reading a paper and the authors read the tt component of the metric from the line element ds^2=f(r)[g(r) dt^2+h(r) dr^2] as g_{tt}=g(r) instead of (what I expect to be) g_{tt}=f(r) g(r) Could somebody please explain to me why? Thank you.

Hello all, I was hoping someone would be able to clarify this issue I am having with the Lie Derivative of a vector field. We define the lie derivative of a vector field Y with respect to a vector field X to be L_X Y :=\operatorname{\frac{d}{dt}} |_{t=0} (\phi_t^*Y), where \phi_t is the...

I understand the use of this rule for the limit as x goes to 0, but not for the limit as x goes to infinity. Can this rule be used to find limits to infinity? How? I have googled this but couldn't find a good explanation.

I know power = Torque x angular velocity (rad/s) AND I am wondering if angular velocity can be calculated through strokes per minute? The product is a reciprocating saw (not orbital). In this case are RPM's the same as SPM'S? Thanks

Homework Statement A force which is at an angle θ to the horizontal (not being 90°) has two components Fx = FCosθ and Fy = Fsinθ along the x and y direction. However, when working out problems regarding objects on an incline, the horizontal (parallel to the slope) component of Normal force...

Hello everyone, I am having difficulty understanding the difference between the basis of a subspace A and and the basis of the range of A. My textbook seems to follow the same approach in determining both. So are they essentially the same?

My understanding of the Einstein Summation convention is that you sum over the repeated indices. But when I look at the metric tensor for a flat space I know that g^{λ}_{λ} = 1 But the summation convention makes me think that it should equal the trace of the matrix g_{μσ}. So it should...

So in class today the lecturer gave a regular map on the set V(s_{1}s_{2}-s_{0}^2) in projective 2-space to projective 1-space by \phi = (s_{0}:s_{1})=(s_{2}:s_{0}). I'm confused. Is that another representation of the "function"? (Meaning they map to the same point classes?) or is it an...

Homework Statement Exercise Find the pressure at a depth of 10 m below the surface of a lake if the pressure at the surface is 1 atm. (Answer: With P0 = 1atm = 101kPa, ρ=103kg/m^{3}, and g= 9.81 N/kg, we have P = P0 + ρgh = 1.97 atm. The pressure at a depth of 10 m is nearly twice that at...

Homework Statement Given the this circuit calculate the voltage through the 3amp source? attached is a jpeg of the circuit. I wasn't able to get a good score on this one question quiz since this boggled me. Is true if I put current source that it will dictate the current of the battery...

Homework Statement See figure attached for problem statement, solution provided and my solution. Homework Equations The Attempt at a Solution I'm getting confused about the reference point for the potential. First find the potential at point z with reference at infinity...

So a well-known theorem from Lebesgue integration is the dominated convergence theorem. It talks about a sequence f_1,f_2,\ldots of functions converging pointwise to a function f. And if |f_n(x)| \leq g(x) for an integrable function g, then we have \int f_n \to \int f. But what if we have a...

Hi guys, Got a question on the naming of the kilo unit. Lets say I've got a battery at 1 kWh capacity, the k is lower case. However MWh, mega is capitalised, so is GWh, TWh. Now on the other end of the scale i can understand it is lower case, mWh, μWh, nWh. And for the large end of the...

A rocket ship of length L (in the rocket's frame) leaves the Earth at speed v. A light signal is sent after it which arrives at the rocket's tail at t'=0 and t=0 according to Earth clocks. My question is: Why is it that the total time (according to earth) for the signal to get to the head and...

Homework Statement I am reading the solution the integral of (log(z))^2/(1+z^2) from 0 to infinity in a textbook, and I'm not sure I quite understand it, and I think this misunderstanding stems from my difficulty w/ branch points/cuts for multivalued functions. Homework Equations...

Homework Statement The problem that was given was to prompt the user to type words with no spaces in between, and end it by pressing enter. From there, the program would calculate which letter comes the latest in the alphabet and is included in what the user types in. example. user types...

Homework Statement I am to integrate cos(2x)/(x-i*pi) from -inf to inf Homework Equations The Attempt at a Solution The problem I'm having is this: I write cos(2x) in exponential form, e^(2iz), so f(z) = e^(2iz)/(z-i*pi). I choose a large semicircle in the UHP as my contour...

Homework Statement When I'm solving problems, I'm told that the time between the vertical and horizontal components are the same. So that means that I would have to use the same time when calculating for both the vertical and horizontal components right? But then there are times when i have...

for the right hand rule for a wire with a current and magnetic field. Your thumb points in the direction of the current and you wrap your fingers around the wire. Do your fingers form a fist or how much do you curl it? Right now, I'm curling my fingers where the tips of my fingers TOUCH my palm...

Homework Statement An elastic string with modulus of elasticity=12. Natural length= 0.5m. Mass of ball attached to the end of the string=0.5kg. The other end of the string is fixed at point P. The particle is pulled down until it is 1.5m below P. Find the kinetic energy of the particle...

Here is my question. For example if i am standing on top of the empire state building and i define that to be height=0 and i define the downward direction to be positive. if i drop a mass does its potential energy increase based on my definition of direction? My actual problem was an exam...

Homework Statement [PLAIN]http://img193.imageshack.us/img193/820/unledoxy.png The Attempt at a Solution OKay I could interpret A as something like {{-...,-...}, {-1,-1}, {-1,-2}...{-1,1}...{1,-1}, {1,1}, {2,...}, {..., ...}} Just a lot of combinations of integers without 0...