# Search results

1. ### Lagrangian- what potential?

1. Homework Statement There is a joint system of rods and masses.We need to set up Lagrangian. 2. Homework Equations L= T-V , T = Kinetic energy , V = Potential energy 3. The Attempt at a Solution Hey what should we take as the zero of potential. So does the Lagrangian depend...
2. ### Following first order rxn

OK if we are given the following first order rxn: 2N_2O_5 - > 4NO_2 + O_2 The rate constant is k. Now how would we express the rate law for the decomposition of N_2O_5. - d[N_2O_5]/dt = k[N_2O_5] OR - d[N_2O_5]/dt = 2k[N_2O_5] I think it is the latter but I see all books use...
3. ### Conductors and fields

I had been reading Feynmann lectures , and in it he has shown an argument which proves that E field inside an empty cavity of a conductor is zero.OK. Now he says a similar argument can be used to show that if there is some charge in a cavity of a conductor than the field outside must be zero...
4. ### Another pH

1. Homework Statement 50ml of 0.10M Na_3PO_4 + 50ml of 0.10M NaH_2PO_4 For H_2CO_3: Ka_1 = 7.5 * 10^{ - 3} Ka_2 = 6.2 * 10^{ - 8} Ka_3 = 1.0 * 10^{ - 12} 2. Homework Equations 3. The Attempt at a Solution Since K_h of Na_3PO_4 > > Ka_2 , I considered only hydrolysis of...
5. ### Find pH of 0.1 MNaHCO3

1. Homework Statement Find pH of 0.1M NaHCO_3 Ka_1 (H_2CO_3) = 4.3 * 10^{ - 7} , Ka_2 (H_2CO_3) = 5.61 * 10^{ - 11} 2. Homework Equations pH = \frac {1}{2}(14 + pKa_1 + logC) 3. The Attempt at a Solution Now K_h = \frac {Kw}{Ka_1} = 2.3 * 10^{ - 8} > > Ka2 So I neglect dissociation...
6. ### Modern Physics

1. Homework Statement A single electron with de Broglie wavelength \lambda passes through a slit of width d = 2\lambda. The electron can then strike a flourescent screen. What will be observed on the screen? a) A diffraction pattern b) A single flash has if the electron had moved in a...
7. ### Center of gravity vs center of mass

Is it different from the center of mass? My book says yes but doesnt answer the question.
8. ### Emfs, work and heat

When we say heat released in a circuit is i^2 RT , who/what is the cause of this energy loss; is it the battery mechanism? Since work done on charge in the circuit by E field is zero, the only other force seems to be the battery mechanism, right? But in text books there is so much implication...
9. ### Lots of forces F1,F2,F3

Suppose we have lots of forces F1,F2,F3 etc acting at a point. Then pressure would be the magnitude of vector sum divided by area , limit of area tending to zero or just sum of magnitude of individual forces divided by area, limit of area tending to zero. Also if we are given a surface and...
10. ### Standing wave energy

1. Homework Statement A standing wave is maintained in a homogenous string of cross-sectional area a and density \rho . It is formed by the superposition of two waves travelling in opposite directions given by the equations y1 = Asin(wt-kx) y2 = 2Asin(wt +kx) Find the total mechanical energy...
11. ### Average value of AC over a complete cycle is always zero

1. Homework Statement Statement 1: Average value of AC over a complete cycle is always zero. Statement 2: Average value of AC is always defined over half cycle. We need to tell whether these two statements are right, and if 1 is right then whether 2 is its explanation. 2. Homework...
12. ### Non collinear vectors

I kinda remember some identity which goes as follows: If a,b,c are coplanar, non collinear vectors then \alpha a + \beta b + \gamma c = 0 => \alpha + \beta + \gamma = 0 or something like this. Can someone help me remember.
13. ### Incompressible viscous liquid questions

Which of the following is true in a streamlined flow of incompressible viscous liquid? A) When a fluid is in streamlined flow then there is transport of energy from one layer to another. B) The speed of flow at all points in space is necessarily same. C) The velocity of the liquid in contact...
14. ### Non conservative

In an inductor capacitor circuit , what is the kind of E field driving the current? Conservative or non-conservative? And I really dont understand what is the correct way to setup the differential equation for it. This is why: In high school level text books(Resnick Walker), they have applied...
15. ### Electric current flow in a circuit when a capacitor is fully charged?

Why doesnt electric current flow in a circuit when a capacitor is fully charged? I mean there is still the battery making the E field, why is it unable to move the electrons of the wire of the circuit?
16. ### Non electrostatic?

I encountered a problem which goes like this: Two charges of mass m and charge q are initially positioned far from each other. Now one is projected towards the other with velocity v . Find the closest distance of approach. We( in class) solved the problem using energy conservation but I...
17. ### Circular motion of rigid body

When considering pure rotation of a rigid body about some point , then can we always consider the body to be concentrated in its centre of mass and use all force related equation treating it like a point object situated at it center of mass.? Why? Can anyone prove mathematically because there...
18. ### Gravitation - Satellite in circular orbit

1. Homework Statement A satellite of mass m, initially at rest on the earth, is launched into a circular orbit at a height equal to radius of the earth. What is the the minimum energy required for this purpose? 2. Homework Equations GMm/r^2 = mv^2/r PE at surface = -GMm/R PE at...
19. ### Organic : Acidity/basicity

1. Homework Statement Which isomer is more basic in the following pairs: o-methyl aniline or p-methyl aniline o-chloro aniline or p - chloro aniline o - chloro aniline or o-floro aniline o-nitro aniline or p-nitro aniline
20. ### Only quasistatic process can be a polytropic process

We may say a process is adiabatic if it occurs fast enough such that no heat is exchanged from the system.But we also say a process is quasi-static when it occurs very slow. Then how can PV^gamma = c hold for a fast occuring adiabatic process because a polytropic process should be quasistatic...
21. ### Sound waves

In many problems , to change the length of the air column we use water but I dont understand why waves dont pass into water and then the reflected wave will have less amplitude and hence standing waves could not be formed.
22. ### Wave mechanics

Can anyone validate that phase always decreases in the direction of propagation of wave? Also if i have a sonometre wire in which i develop a transverse wave using a tuning fork and then i immerse the weight into water i.e change the tension, will the frequency also change? I mean frequency...
23. ### Capacitor problem

1. Homework Statement The space between the plates of a plane capacitor is filled with a dielectric of constant k. The plate gets a charge of surface density L_0 . Determine the force per unit area that is exerted by the field on the dielectric. 2. The attempt at a solution...
24. ### Gauss's law doesnt work here?

So I was doing this one problem in which there is a sphere of radius r and charge density row and there is a spherical cavity inside it whose center is at a distance r2 from the center of the bigger sphere. Now the question was what is the E field inside the cavity. My first and long...
25. ### Many organic related

1. Homework Statement 1)(CH_3)_3CCH(OH)CH_3+ HBr -> I believe reaction should be elimination because Br^ - is a weaker nucleophile than OH^ - so it cannot substitute it. 2)CH_3CH_2CHBrCH_3 + EtO^ --> Substitution? 3) Compare the nucleophilicity ofNH_3 and PH_3 NH_3 has more e^ -...
26. ### Use Kirchoff's loops rule in the circuit?

The emf given -\frac {d \Phi}{dt} produces a non conservative field right? Then is it right to use Kirchoff's loops rule in the circuit? Also if a coil with self induction L, is kept in a constant magnetic field perpendicular to the plane of the coil, and the flux associated through the coil...
27. ### Massless body

What happens when the NET force on a massless body is 0. I mean what will be the acceleration , if any? Also if we pull a massless spring, from one side with a force F1 and from the other side a force F2, what will be the spring force?
28. ### Vector v = a i +bxj

I have a vector v = a i +bxj Now I want to find a.So I apply chain rule and differentiate dv/dx * dx/dt = bj * Vx = bj*ai ?? Now what does this mean? Is this allright? Should I not care about the vector directions when differentiating and just use the magnitudes a = ab , if yes then why? And...
29. ### Power in circuit

OK if we have a circuit with a battery of emf e and internal resistance r and external resistance R. We are given that the current in the circuit is I. What is the thermal power generated in the battery and the power developed in it by the electrical forces. OK straightforward "formula"...
30. ### Sphere rotation expression help

1. Homework Statement 1) A sphere of radius R is projected up an inclined plane of angle @ with initial speed Vo and angular velocity Wo in a direction in which it can roll.The coefficient of friction is tan@/7 and it is given that Vo> RWo. Obtain an expression for the total time of motion of...