Recent content by nuclear_dog

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    Problem related to the vector potential of B

    Thanks, that actually solves the problem. Although I will have to read up on the identities of vector calculus to feel satisfied on this question.
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    Problem related to the vector potential of B

    haruspex , I got hold of the original question paper today and have attached a screenshot of it. Please take a look at it to clearly understand the question , since I might not have explained it properly. Since (dp/dt) = F = q(vXB) , hence if we can show that ∇X{d/dt( p + qA)} = 0 , it would...
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    Buoyant force in seawater and freshwater

    Your thinking is correct. Let us say that an object is submerged to a volume V in a given fluid . Then the fluid applies a force on the object ,which is equal to the force on an equal volume V of the fluid due to the rest of the fluid body. This force is equal and opposite to the weight of the...
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    Help me proving this Kinetic Friction Coefficient

    Is there any condition given that M >> m . since in that case (1 + m/M) will tend to 1, and your expression will reduce to the required expression. I am also getting the same answer as you got.
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    Problem related to the vector potential of B

    I am sorry I forgot to add that in the question it was given that since ∇.B = 0 , therefore we can write B = ∇XA , where A is a vector. So I am not sure that we can use the transformation of ∇ in the expression.
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    2012 F = ma Contest, Problem 24

    Are you getting the same answer by keeping one end tied to the center of the triangle. If one end is tied , then k*l = m*2l*(ω^2) which means k = 2m(ω^2)
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    Problem related to the vector potential of B

    Homework Statement A particle of mass m and charge q moves in a region with a magnetic field B(r) which is time independent. What is \frac{dA}{dt} as seen by the particle. Homework Equations The Attempt at a Solution Since the B field is not varying with time, I know that the change in A will...
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    Doubt regarding derivation of bound charges in dielectric

    Thanks , I can see that in Cartesian coordinates .
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    Doubt regarding derivation of bound charges in dielectric

    In Griffiths, for deriving the bound charges for a given polarization P , the formula used is the general formula for dipoles .i.e ( equation 4.9) {Here the potential at r is calculated due to the dipole at r' ) V(r) = ∫\frac{x.P(r')}{X^2}d\tau' Here X = r - r' , and x = unit vector in...
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    Programs Can I get a Ph.D. in physics if my bachelor's degree isn't in physics

    Just wanted to add , that in India students who wish to go for masters in physics have to appear for a national level test called Joint Admission test for MSc (JAM) . The questions are of the level that any above average physics BSc student can answer . I think they can also serve as a good...
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    Problem 5.15 of Statistical Physics by Reif ( Calculation of entropy)

    Thanks for the reply. What I wanted to know was, whether the entropy change of only the water in the two cases would be same or not. By the method I have used, I get the same entropy change for water in both the cases.
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    Problem 5.15 of Statistical Physics by Reif ( Calculation of entropy)

    Homework Statement 1 kg of water with specific heat (C) of 4180 Joules /kg/degree is given at 0°C. It is taken to 100°C by two methods :- (i) by bringing it in contact with a reservoir at 100°C. (ii) by bringing it in contact with a reservoir at 50°C , and then with another reservoir at...
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    What is the Velocity of the Last Angstrom in the Falling Chain Problem?

    I am sorry, I made a mistake in my previous post. The mechanical energy of the entire chain would not be conserved , as some of this energy will be used to increase the internal energy of the table on the collision . So , the part of the chain which has not yet touched the table can be assumed...
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    What is the Velocity of the Last Angstrom in the Falling Chain Problem?

    Well ,there are only two forces acting on the chain , namely the gravitational force and the reaction forces . Now , the reaction forces do not do any work on the chain , as at their points of application , the displacement is zero. Therefore the net mechanical energy of the whole chain is...
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    Need help Can anyone tell me ways physics is related to the brain?

    you could read some books related to theoretical neuroscience, such as the one by Peter Dayan , to get a feel of the subject . But I feel as a physicist you will be disappointed at the lack of "theory" in neuroscience at present. there are a lot of " models " which have been proposed , but they...
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