Doubt Definition and 591 Threads

Hi. I'm studying Finite Elements Method, I was readding a paper written by Danielle Boffi and in a part dedicated to the approximation of eigenvalues in mixed form, it's about approximating eigenvalues in the Hilbert Spaces \Phi and \Xi Then it says: "If we suppose that there exists Hilbert...

in rigid body dynamics is this relation between velocity of centre of mas and velocity of any particle in the rigid body correct? vcm = vp + rXω r is the position vector of the particle with respect to centre of mass relations are written in vector form and also tell me how to calculate...

Hey, can the Space Time Fabric be ripped or broken? The answer could help find the state of the universe on some aspects.

Consider the following circuit with Vs=1V, R=1Ω and C=1F. The voltage transfer function of the resistor can be written as Vr(s)/Vs(s)=s/(s+1). Now I understand s is complex frequency and at s=∞ the transfer function becomes unity since capacitor acts as a short and Vs=Vr. What I don't...

what is electric current...a scaler or vector?? ...well I personally believe that it is somewhere in between the two extremes (what is not 0,need not be an 1 either :oldbiggrin: ) ...particularly because of the strange similarity we see in vector addition and phasor addition)...some people...

I am using Spivak Calculus. I have a general doubt regarding the definition of least upper bound of sets. Let A be any set of real numbers and A is not a null set. Let S be the least upper bound of A. Then by definition "For every x belongs to A, x is lesser than or equal to S" Let M be an...

Can the phase stationary method be applied to complex functions? And if it does, is it still called phase stationary method? I ask this because there are several methods for asymptotic analysis and I need to be sure if I can use this method for complex function. Is there any difference with the...

Hi, there. I remember when I was in the University (mech. engineering), I had an exam on partial differential equations about heat transfer in a cylinder. We had to determine the temperature distribution. I remember the conditions were that the cylinder was insulated in the side area, had a...

i have studied that a conductor is equipotential and charges don't flow through it but how does it flow through a wire?

My textbook says that net rate of heat transfer due to radiation is εσA(T^4-To^4) but i couldn't understand it. Rate of emission is εσAT^4 and rate of absorption is aσATo^4 so net rate of heat transfer must be εσAT^4-aσATo^4(where T is the temperature of body and To is the temperature of...

in fluid statics we have learned that p =patm+density*g*h. is the same equation valid in fluid dynamics?

i know that all conductors are equipotential,then how are charges flowing in a conductor?and at times in we say that charges won't flow since two points are equipotential(like in wheat stone bridge we say that charge won't flow across the capacitor/resistor since the ends of the 5th...

in deriving the capacitance of a parallel plate capacitor why do we take the field between the capacitors as σ/∈ and not 2σ/∈,when there are two plates and in the region between the capacitors, field must add up so shouldn't it be 2σ/∈?

Homework Statement Please see this illustration http://www.physicsgalaxy.com/lectures/1/57/1006/Solved-Example-1#6 (see question only) Homework Equations potential due to a hollow sphere at it's centre = kq/rThe Attempt at a Solution here won't there be an induced positive charge on the outer...

Homework Statement http://[url=http://postimg.org/image/f7e6kp0xv/][PLAIN]http://s21.postimg.org/f7e6kp0xv/image.jpg Homework Equations Kepler's laws The Attempt at a Solution I thought the answer will be C : I and II But the solution written (it was my friends book) is B, which is correct?

Homework Statement Find the magnitude of an electric field intensity at a distance 12.9 cm, from the axis of a long, straight conductor, which has a radius 3.82 cm, and a charge density of 1.61 C/m. Homework Equations Gauss's law The Attempt at a Solution E= λ/2πrε0 Hello, I'm having some...

for static fluids we have studied that p=patm +density*g*depth. and this equation is derived from Newton's laws,but in fbd why didn't we consider the force exerted by curved surface area of container,it doesn't cancel out when containers are in frustrum shape.and the vertical components add up...

in Newton's laws of rotational motion, is the net torque calculated only about centre of mass?or is it valid for torque about any axis?

in parallel axes theorem in rotational mechanics,is it necessary that the axes must intersect the body?

in this video http://www.physicsgalaxy.com/lectures/1/44/234/Solved-Example-2#12(see only the question) the method illustrated is integration but i thought of an alternate method, moment of inertia of half disc with radius r2 is 1/2mr2^2 and that of half disc with radius r1 is 1/2mr1^2.so...

please explain the phenomenon of friction acting on a car moving in a circular track.also explain how is this friction static and how is this friction different from the friction acting on a car moving on a straight road.

For someone who's familiar with the de Broglie relation it's easy to say that for k=0 we have p=0 but how would we know that before deriving the result? In this image the author derives de Broglie relation by considering a wave packet in motion. As you can see where I have star-marked the author...

Two doubts: First, when the hammer hits any string, the string begins to vibrate, until here, no problems, but, the vibration decays over time and this decay is linear, exponential or assume another form? Second, when the hammer hits a string and the string begins to vibrate, it vibrates in...

So we know that an object undergoing horizontal circular motion, has a angular velocity with direction perpendicular to the plane of motion, and also a linear velocity with a direction perpendicular to the acceleration towards the centre of motion Question : if we sum/add the linear+angular...

in string pulley systems(like atwood machine),the string applies a force on pulley of force 2T downwards,but why is it so? why should it apply that force? explain in detail

I'm trying to start understanding quantum mechanics, and the first thing I've come across that needs to be understood are black bodies. But I've hit a roadblock at the very first paragraphs. :( According toWikipedia: A black body (also, blackbody) is an idealized physical body that absorbs all...

I can't be the only person to ever have this thought so I am hoping one of you star gazers can tell me what I am missing. I understand Hubble's theory and the idea of space itself expanding. My question is this. If we know the universe is expanding because of the redshift and the farther away we...

Alright I was doing some basic questions on ray optics when this doubt came to my mind So my doubt goes like this:(IT may be silly) Consider a concave mirror with pole P and centre of curvature C Its principal axis is extended on both sides Now consider a ray parallel to the principal axis Call...

Electric flux through a closed surface S = q/ε0 (1.31) q = total charge enclosed by S In the situation when the surface is so chosen that there are some charges inside and some outside, the electric field [whose flux appears on the left side of Equation above is due to all the charges, both...

Good evening people. Recently I started taking the "electric network analysis" course in my school. We already saw the mesh analysis method for solving circuits. Now we are seeing the node analysis method. I understand that the first step for this method is finding the number of nodes (and one...

Hi, in order to upgrade my knowledge in dynamics, I am starting a more advanced course by myself, and the two recommended books were Principles of Dynamics and Advanced Dynamics, both by Greenwood. I would like to know what is the difference of this two books, which one is harder? Thanks anyway.

I'm trying to solve an exercise that asks what is the final speed of two positive particles after they are very distants each other. Then I've used the conservation of energy to solve it. The initial energy of the system is the potential energy = Q².k/d The final energy is the 2 knetic energy of...

Homework Statement Hi everyone. Here's my problem. I know that the volume element in spherical coordinate is ##dV=r^2\sin{\theta}drd\theta d\phi##. The problem is that when i have to compute an integral, sometimes is useful to write it like this: $$r^2d(-\cos{\theta})dr d\phi$$ because...

Hello people . Just joined this community after google answered my doubts with this site

Our teacher derived an expression for electric field due to thin sheet using gauss law which was sigma/2*epsilon naught which was independent of r but dies that mean the field will be same even if r is 10000km but field is also equal to kq/r^2

Hey everyone, I have this doubt for quite some time now. So could somebody please help me and explain where I am going wrong with this. According to the relativity of simultaneity, it is impossible to say in an absolute sense whether two distinct events occur at the same time if those events...

Each chromosome of a bivalent attaches with two spindles in metaphase.It's correct,right? as i can see from the below image but my book says it's wrong.and i am confused because i can see different types of images according to the image below each chromosome of a bivalent attaches with three...

Suppose there is person A in a frame S with respect to which a light beam clock is at rest , now time taken by a photon to go from bottom to top is L/c according to A. now the same clock is looked at by a person B traveling with velocity v w.r.t S and according to him time taken by photon to...

Hi, I wonder if what I think is in according to the theory in Why the liquid falls. Check out the image I've uploaded. (sorry my bad english)

suppose person B was standing with person A at some point O and now person B starts to move with velocity c/2 w.r.t A on a straight track(starting from O) and both the observors(A and B) start to note time on identical clocks attached to their respective frames .Now after 1 second (according to...

If electron can show behaviour of wave in double slit experiment like interference, diffraction, can it pass through fibre optic cables, if it is accelerated with high speed into the cable?

I will try to explain this with an analogy. Let's have this equation: x^2 =9 And let's assume I don't know algebraic methods to solve it, so I create a list using excel with different values. And I see that if I put x=4 it doesn't work, if I put x=5 it is even worse and so on. But If I put...

Hi, I'm programming a simple DLL to use VSOP87 and ELP82b. I can get the correct x,y and z values without a problem referred to J2000, I think. But I'm getting a constant error when applying the correction for the nutation and precession in ELP82b. Actually, I'm getting even worst values than...

Today, I had a class on Complex analysis and my professor wrote this on the board : The Laplacian satisfies this equation : where, So, how did he arrive at that equation?

Hey everyone! I'm doing this simple exercice from Halliday's book, where I have to find some intensities at some points... anyway after solving it, I realized that only looking at point b,and using Kirchoffs loop rule, the voltage at the negative of E1 and the voltage at the negative of...

Homework Statement A metal ball is connected to the ground with a wire via a switch. The switch is initially closed (i.e.the ball is connected to ground) while a charge +Q is brought close to the ball (but not touching). While the charge is near the ball, the switch is opened and then the...

Homework Statement Actually I have two doubs, the first one is Why in the solution of this problem, in the sumatory of moments in C, Force 2=10?? If in the sumatory of moments in F, Force 2 is 416.7 N. Actually I calculate with 416.7 N, and T in C = 100 N. The other doubt is with the sign...

Homework Statement Calcular the force P when a bar starts yield, when 2 bars start yield, and when the 3 bars start yield Diameter = 25 mm (for every bar), Yield Stress of Steel = 250 MPa. Homework EquationsThe Attempt at a Solution [/B] [F][/AD] + [F][/BE] + [F][/CF] = P 2[Δ[/AD] -...

Force" F"is applied on M1 .Although force applied is not directly on M2,but it will also experience this force" F" via M1,right? But I don't think it is correct.Because it implies that no matter how big the force on M1,the net force on M1 will always remain zero.And there will be unbalanced...

Hi everybody, I was messing arround with the program stellarium; I decided to check the hour angle of the sun at 10 am on August 12; it was 19h 53 min; then I did the same for september 4th and it was 20h 0 min. As far as I know it takes 23h 56 minutes to the sun to cross the same point in the...