What is Impossible: Definition and 298 Discussions

An insulated Thermos contains 122 g of water at 91°C. You put in a 13.7 g ice cube at 0°C to form a system of ice + original water. Use mc(ΔT) |water + mc(ΔT) |ice + Lm |ice = 0 Final T = [(m*c*T) |water + (m*c*T) |ice - (L*m) |ice] / [m*c |water + m*c |ice] Final T =...

A 3.40 kg block is pushed along the ceiling with a constant applied force of 85.0 N that acts at an angle of 55.0° with the horizontal, as in the figure below. The block accelerates to the right at 6.00 m/s2. Determine the coefficient of kinetic friction between block and ceiling...

x / y = z, so z * y = x 1 / 0 = x, so x * 0 = 1 But 0 does not equal 1, so x / 0 is unsolvable. Oh, and I'm new to forums so if this shouldn't be here you can delete it.

I was having a discussion with my friend the other day. He had just attended a lecture about Paul traps. He told me that the Paul trap potential has a stationary point in the middle, which is a saddle point, and that the 2 pairs of opposite poles are oscillating between being positive and...

It is often said that superluminal communication is prohibited by special theory of relativity. Do you think this is true? I have doubts about this claim. Imagine a communication between two astronauts in two distant inertial frames A,B with any mutual velocity. Suppose that both...

Okay so I started my first calculus based physics class, the first day I realize he has a very bad accent but I feel like I might be able to understand him. The second day we really start getting into vectors, magnitude, cross product, dot product, etc, I'm sure the supposedly really easy...

So they give me the equation 3y2=x(1-x)2 The idea is to find the surface area of the volume obtained by rotating around both axes. So let's start with a rotation around the x-axis, I decided to rewrite the equation as: y=√(x(1-x2)/3) I know that the surface area for a parallel...

I have a question about why y=(-2)x is impossible to graph and I don't know what to say because I know that with some graph paper and a chart of values I can sure graph it pretty easily but my computer graphing program won't do it. Why not? Why is it "impossible" ?

I expect to be shot down in flames but I don't mine one bit. I have just done a bit of a drive in my 28 year old Nissan Bluebird Wagon about 10% city 90% HWY...NO Fancy EFI systems or direct injection here just a plain old carburetor running slightly rich at idle. I just did a rough...

I'm starting my junior year this fall as a physics & math major, in order for me to apply or even make myself available for co-opts or internships at my University I will have to have a resume' to post on their website. The problem is I have no prior work experience, I don't know what to put on...

So I found this video, in witch it was said and explained that all movement should be impossible .. it was explained somehow like this (too bad i can not find the video now) : imagine a arrow (or bullet.. or anything else) shooting/ moving from start to its target - in order to get to the...

Homework Statement http://www.math.poly.edu/courses/ma0914/past_exams/MA0922_Final_2000-12-13.pdf First problem on the exam Homework Equations I believe the answer should be a 3rd degree polynomial so Ax^3+Bx^2+Cx+D The Attempt at a Solution Ax^3+Cx -8A-2C=0 8A+2C=0 -A-C=3...

We have particle accelerators on Earth that can speed up particles to near the speed of light. Earth itself is hurtling through space, as is the solar system and galaxy that its a part of. If an observer were to float outside of our galaxy and observe those speeding particles in the...

Here's something to drive your friends crazy. Take a 3-by-5 file card and cut it on the solid lines. Crease it on the dotted line. *---*-------*---* | | | | | | | | | | C | | | | | | | | | | | | |...

Take two: This post evaluates the concept of an infinite lapse/passage of time and concludes that an infinite lapse of time is impossible, which was proposed in the sixth century AD by John Philoponus. Likewise, models of cosmology that require infinitely lapsed time such as models of a...

Hi, I have a question that has been bugging me for a while. I was on a ship where the vessel was rolling from left to right. On board the ship was a sled with angled sides of ~ 60°. the mass of the sled looked to be about 50 Tonnes and the only thing stopping the sled from moving around...

Anthony Aquirre and Steven Gratton in 2003 developed a speculative physics hypothesis that includes a timeless generation of time. [1] However, Aquirre in 2007 argued against his 2003 hypothesis of timeless origins while hypothesizing the notion of a past infinite time's arrow. [2] This post...

If another galaxy were to be traveling towards us at the speed of light and as well as the Milky Way being ripped apart or merged, our planet were to suffer a direct hit, we would never know about it! Gone in an instant! Also, we would not know, or do not know, of the existence of such a...

Is it really impossible that gravity can be modeled non-geometrically? I read the following in Weinberg paper Gravity: "An alternative way to conceive of gravity would of course be to follow the lead of other theories, and regard the gravitational field as simply a distribution of...

Obviously it's impossible, but no one on a different forum understood why not in terms of forces. Also the solution doesn't need to be quantitative. Homework Statement The one thing I'd change from the troll science picture below would be to change the balls full of air on a string to a...

Hello, I was under the impression that a dirac delta was a "legitimate" state for a particle: maybe not mathematically, but least physically. But I was recently told by a post-doc in QM that if your particle is in a dirac delta state at one moment, the very next moment the particle is...

Why is it impossible to change the number of protons of an atom? Is it because the protons are in the nucleus? How can we change the number of neutrons then?

This is NOT homework, I am not in this crazy of a class... Homework Statement \displaystyle \int^{45}_{0}\frac{\sin^2(\arcsin(\frac{t \sin \gamma }{ r })-\gamma+180)-\sin^2(\arcsin(\frac{t\sin\gamma}{r})-\gamma)}{\sin^2\gamma}\Delta\gamma r = 1, t = \sqrt{2} Homework Equations The...

Impossible scenario?!? Aargh, pleeaase help me wrap my head around this whole relativity thing. We just started the chapter on relativity at uni and our professor is telling us light speed is invariant and wants us to contemplate an impossible hypothetical scenario for next class! Help...

http://arxiv.org/PS_cache/arxiv/pdf/1111/1111.0301v1.pdf Hi everyone! I'd like to get a little discussion started on what you guys think about this paper if you have the time to read it. I find it really fascinating that they came to the conclusion that up-tunneling is impossible for...

So, yesterday in class we were asked to try and solve the following problem: Given a, b \in R with a < b, draw the graph of an example of a continuous function f such that f: [a,b] \rightarrow R, f(a) = f(b), and there does not exist c \in (a, b) such that f'(c) = 0. Now in class we arrived at...

My question is, is it still widely believed that an all encompassing "theory of everything" exists for the universe? It seems to me that due to quantum mechanics it would be impossible to actually observe enough data to predict precisely the behavior of quarks and other subatomic particles, one...

1. Why is the following situation impossible? A freight train is lumbering along at a constant speed of 16.0 m/s. Behind the freight train on the same track is a passenger train traveling in the same direction at 40.0 m/s. When the front of the passenger train is 58.5 m from the back of the...

Homework Statement A plane lies inbetween two points A=(2,0,2) and B=(4,2,0). Let a point P=(x,y,z) be equally far away from A as from B. Find the equation for this plane (like in this format: http://upload.wikimedia.org/math/6/7/8/67834a730a04bb1f3d6ceab80f5284e4.png ) The Attempt at a...

Hi, I really need some help here.. Vectors remind me why I hate geomtery. problem 1: Prove that |UxV|2 = |U|2+|V|2 - (U*V)2 How can I prove that these two are equal without spending 1 hour using algebra? Maybe there is some geometry quirk that I'm not seeing? problem 2: We have two vectors...

A gigantic machine that has let's say another 1000 machines inside of it. We start the primary machine to travel at 100 km/h. We send it out to space, then the machine sends the next machine inside of and kicks it to give it a boost for another 100 km/h. Now the kicked machine has an extra 100...

This question was on my mechanics test but I skipped it. It seemed kinda crazy. Homework Statement In the drawing is described a weightless beam AC connected to the wall through joint C. The beam is supported by two cables, BE and AD, connected to the wall. At the end of the beam at...

Consider a point P inside a triangle ABC. Angle PBC is 10 degrees, angle PCB is 20 degrees, and angle BAC is 100 degrees. Find angle PAC. Question is that is this problem even solvable? I found it in an Olympiad training book...

Homework Statement http://img835.imageshack.us/img835/7509/appearsimple.jpg Long story short: A is fixed to the ground. Point C is a pin joint. W = 200 [N] The rest is what you see is what you get. The Attempt at a Solution I get too many unknowns no matter what I do. If I look...

Undergraduate "handicap and/or impossible to get ahead" predicament. Need help :( Good evening all, I know I have recently posted several graduate questions recently as I was trying to think out/plan ahead. In doing so, I did some reading and research, particularly on this physics gre...

I have long been puzzled by the whole idea of delayed choice experiments with photons. In a photon's frame of reference there is no distance traveled between emission and absorption; the distance has contracted (Lorentz-Fitzgerald) to zero. More relevantly there is no time duration either...

Current increases up to a certain point, and then decreases until it reaches zero. Then it does the same thing in the other direction. Here's my problem. Without the inductor, the current would not increase over time: it would decay until the two plates had equal charge. With the inductor, I...

Homework Statement A differentiable function g: R --> R such that f' is unbounded on any interval of length one Homework Equations The Attempt at a Solution It's probably easiest to look at [0,1]...maybe something that goes to infinity as it approaches 1? But not sure if it would...

Homework Statement A sequence of Lipschitz functions f_n: [0,1] --> R which converges uniformly to a non-Lipschitz function Homework Equations a function f: A --> R is Lipschitz if there exists a constant M \in R such that |f(x)-f(y)|<=M|x-y| The Attempt at a Solution I don't think...

Hi guys, I have a question re: random numbers and probability. If I have a random number generator that generates a number between 1 and 10, and say I generate a kazillion of these numbers, then doesn't each number have the same probability of showing up? So then, after a kazillion numbers, I...

Homework Statement An open set A contained in R (reals) such that the closure of A = R, but R \ A is uncountable Homework Equations I guess knowing that for the closure of a set A to be equal to R means that A is dense in R? The Attempt at a Solution Every thing I try seems to...

1. integrate 1/(1+(xx-1)^0.5) I.E. Integrate 1 over the sqaure root of( x^2 - 1) 2. I started by rationalizing the fraction and then i split the equation into two. I THEN let x = root2 (tanh(u)) for the 1/(xx-2) fraction, and have no idea what to do from there :S

Hey, It seems like this is impossible because momentum conservation is violated. I had a Q where an electron underwent an energy transition and emitted a photon, and then they asked whether it was possible for the photon to be reabsorbed by the electron to undergo the same transition as...

Hey, Is the only reason for a perpetual motion machine being impossible, both in theory and in practice, simply due to friction? Because there are substances, such as superfluids, and potentially other forms of matter that could be discovered in the future where there is zero friction, so would...

I think I got close to finding the answer to this one, but I'm in a lot of doubt. The problem looks deceivingly simple, but it's impossible to solve. Any scenario I can think of seems to violate some physical law. Goes like this: You have a train car on a frictionless track. It's filled with a...

Find a basis for the subspace S of R^3 consisting of all vectors of the form (a, 2a-b, b)^T, where a and b are real numbers Relevant equations would really just be the determinant of the system. I have tried so many 3x3 matrix combinations of the given form but no matter what the determinant...

Is it possible to have a good relationship when the two people don't basically agree on politics? Granted, some people can agree that it's good to differ but what if they differ in the most fundamental beliefs about politics? E.g. what if one person really likes a certain politician, party, or...

Hi guys, I came across this in a textbook, it says its as good as impossible to integrate this expression. I've met a lot of smart guys on here, maybe someone can do it? \int exp (-x^2) dx

Game Theory a problem which is a bit similar to the "Impossible Puzzle" From numbers 1 to 10, two integers X, and Y (not necessarily distinct) are chosen by a referee . The referee informs secretly to Joe the integer U where U = X + Y . The referee informs secretly to Bob the integer V where V...

I am not a physicist, so please excuse the gaps in my knowledge. I am writing a would-be philosophical essay about models in different fields of research. In most general terms, my task is to consider how modelling can be useful in the pursuit of knowledge in the widest understanding of the...