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1answer
27 views

Time difference in clocks of an accelerated frame

If we have two inertial frames $S$ and $S'$ and $S'$ is moving to the right w.r.t. $S$ with a velocity $v$. Suddenly $S$ undergoes negative acceleration (no longer being inertial) and after some time ...
1
vote
0answers
31 views

Double dot product in Cylindrical polar coordinates - Strain Energy

I'm working with a problem in linear elasticity, and I have to calculate the strain energy function as follows: $$2W=σ_{ij}ε_{ij}$$ Where σ and ε are symmetric rank 2 tensors. For cartesian ...
0
votes
1answer
35 views

Calculating force of a car

I'm simulating car cruise system and my results are not making any sense. I have been told that my force formula is wrong but I don’t understand why it is wrong and how I can fix this. Does anybody ...
-2
votes
0answers
15 views

Geffen's Ladders Distance [on hold]

The Geffen Mage Guild decided upon some touch-up repairs to the Geffen Tower, and contracted with the Alberta Mercantile Guild for work. While setting up, the Merchants placed two ladders ...
0
votes
1answer
42 views

Showing a fourth rank tensor in $\epsilon$'s reduces to one in the metric $g$

Consider the fourth rank tensor $$S_{\mu \nu \rho \sigma} = a(\epsilon_{\mu \sigma}\epsilon_{\nu \rho} + \epsilon_{\mu \rho}\epsilon_{\nu \sigma})f(x^2),$$ in 2D where $a$ is a constant and $f(x^2)$ ...
-1
votes
0answers
21 views

Runs of a vacuum pump? [on hold]

After how many runs of a vacuum pomp with volume $v$, the initial pressure $p_i$ of a balloon is reduced to a final pressure $p_f$? Baloon's volume is $V$ ($V>v$).
0
votes
1answer
58 views

Moment of inertia of a cylinder about its base

I've tried to find the moment of inertia of a cylinder rotating about an axis parallel to its base (i.e about the 'End diameter') as one can see here . But when I checked my results with different ...
-2
votes
0answers
33 views

Determine unknown potential & Hamiltonian in Schrödinger equation [on hold]

$x$ - time dependent Cartesian coordinate ; $m$ - time dependent mass of particle; Potential energy - unknown ! Hamiltonian - unknown ! Tasks: Make a formula to predict the $X(t$) ($x(t)$ for ...
0
votes
2answers
36 views

Deriving spring oscilation period

We have a spring attached to a wall and at the other part an object on a frictionless surface. I tried to calculate the spring oscilation period. I used the conservation of energy and kinematics ...
-1
votes
0answers
23 views

heat supplied by two heat source in reversible heat engine [on hold]

A reversible engine is supplied with heat from two reservoirs at 900 K and 600 K and rejects heat to a sink at 300 K. The engine develops work equivalent to 90kJ/s and rejects heat at the rate of 56 ...
2
votes
3answers
110 views

Describing a circular current loop as delta functions

It would be really nice to see how Jackson got eqn 5.33 on his example problem for finding the vector potential of a circular current loop $$ ...
1
vote
1answer
57 views

Distance and velocity question

I know that speed is the derivative of distance. So integrating speed should give you distance. Let's suppose we have a speed which obeys this function: $$ v(x) = 2^{2^x} $$ So at time 0 the speed ...
0
votes
1answer
36 views

How to show that the gravitational potential energy of a two particle system is -2 times the total kinetic energy, without using the virial theorem?

Consider a two-particle system with identical masses, orbiting in circles about their center of mass. I'm supposed to prove that: $$U_p = -2U_k$$ With $U_p$ potential energy of the system, and $U_k$ ...
0
votes
0answers
23 views

Help With Wakefield Integrals With Implicit Variables [on hold]

My calculus is really rusty (damn Mathematica/Matlab) and I was wondering if anyone could help me with an equation I am having trouble integrating. I have attached a snapshot of the paper I am trying ...
0
votes
1answer
41 views

The commutator of Killing vectors

I'm going over an assignment for my general relativity course. My solution to the question below strikes me as too short, considering that it appeared in the "longer questions" section of the ...
-3
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0answers
31 views

Determine the emf [on hold]

A meter long metal rod of mass m is falling with a constant velocity of 10 m/s. The rod is attached to two conducting rails. Determine the emf if there is a uniform magnetic field directed ...
-1
votes
0answers
15 views

Obtain the electric field [duplicate]

Let $V=(xyt^3T)j+(x^4tT)k$. Find the curl of the magnetic field and the electric field. The curl I found to be $-(4x^3t)j+(yt^3)k$ It's sensible to leave out the units T right? How do I find the ...
-1
votes
1answer
41 views

Determine the electric field [on hold]

A loop of wire is put in a changing magnetic field. The magnetic flux through the loop is given by $4t(t+2)$. The loop is connected to a parallel plate capacitor that has a plate separation of 15mm. ...
-1
votes
0answers
18 views

Mechanics Dynamics_Kinetics [on hold]

Figure shows an engine (e.g. IC engine, electric motor, turbine, etc.,) coupled to a load through a common shaft. The engine generates or supplies energy to the load, whereas the load absorbs the ...
-2
votes
0answers
61 views

Find the electric field [on hold]

Let $V=(xyt^3T)i+(x^4tT)j$. Find the curl of the magnetic field and the electric field. I've found the curl. The curl I found to be $-(4x^3t)j+(yt^3)k$ It's sensible to leave out the units T right? ...
-1
votes
0answers
23 views

Vectors-a tricky problem [duplicate]

A particle subjected to two equal forces along two different directions. If one of the forces is halved, the angle which the resultant makes with the other is also halved. The angle between the forces ...
-1
votes
0answers
15 views

Sound Interference Practical [on hold]

ok so we did an experiment where we put speakers 1.5m apart and played a frequency of 330hz. then we had to walk around and find quiet spots and loud spots. the questions we have been given are a bit ...
-2
votes
1answer
52 views

An interesting problem on vectors [on hold]

A particle subjected to two equal forces along two different directions. If one of the forces is halved, the angle which the resultant makes with the other is also halved. The angle between the forces ...
0
votes
1answer
22 views

Area covered by particle between it's path and horizontal lines

Question: The maximum range of projectile is $R$ and the maximum height attained by the particle is H. If the area covered by the particle between its path and horizontal line is $A$, then ...
1
vote
0answers
38 views

calculate force between two magnets [on hold]

I have used a couple of online calculators to estimate the attractive force between two cylindrical bar magnets. Using d=1"; t=1"; x=0.1"; Neo35 (Br=12,300 Gauss): source 1 gives 63.5 lbf source 2 ...
0
votes
1answer
55 views

Classical mechanics; gravitation question [on hold]

There is a crater of depth $R/100$ on the surface of the moon (radius $R$). A projectile is fired vertically upward from the crater with a velocity, which is equal to the escape velocity from the ...
1
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0answers
46 views

Lagrangian for FRW metric

For the metric $$ds^2=-dt^2+a^2(t)(dx^2+dy^2+dz^2),$$ $$L= \sqrt{-g_{\alpha\beta}\frac{dx^\alpha}{dt}\frac{dx^\beta}{dt}}$$ How does this become $$L= \sqrt{1-a^2 (\frac{dx}{dt})^2}~? $$ I guess ...
-3
votes
0answers
27 views

How to calculate integral? [migrated]

$\int_0^\infty\mathrm{d}l/(r^2+l^2)^{3/2}$ the solution is supposed to look like this, unfortunately I can't derrive it.
0
votes
2answers
28 views

Finding Interatomic Spacing

Here is the problem I am working on For what temperatures are the atoms in an ideal gas at pressure P quantum mechanical ? Hint: use the ideal gas law P V = N kT to deduce the interatomic spacing ...
0
votes
2answers
25 views

Work done by a frictional force on a cylinder

A cylinder of mass $m$ and radius $R$, is rolled on surface with coefficient of kinetic friction $\mu_{k}$ about the axis passing through the center and parallel to the surface, with initial ...
4
votes
2answers
137 views

Gravitational slingshot maximum

I have recently read an article about gravitation slingshot assist used by Voyagers 1-2, and was thinking on why this hasn't been used for travel between solar and other systems. I mean sligshot can ...
1
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2answers
46 views

Rotational inertia of a ball

This question refers to the solution of problem 12 here. It involves a spherical shell of mass $M$ filled with frictionless fluid of mass $M$ rolling down an inclined plane. (This is problem 12 of ...
0
votes
0answers
22 views

How to find this torque? [on hold]

If I want to calculate the total torque, will it be $\sum$$\tau$$=$ $T_1$$l_1$$-$ $T_2$$l_2$$=$$I$$\alpha$ or $\sum$$\tau$$=$$T_1$$l_1$$-$$(T_2+mg)$$l_2$$=$$I$$\alpha$
0
votes
0answers
51 views

Variation of the action respect to the metric, integration by parts, variation of ricci tensor [on hold]

Im doing the variation respect to the metric of \begin{equation} S=\int d^4x \sqrt{-g} \{\frac{1}{2} R_{\alpha \beta} A^\alpha A^\beta \} \end{equation} Es decir, \begin{equation} =\frac{1}{2} ...
0
votes
1answer
190 views

What strategy should I use to approach this problem? If my straight line approximation doesn't work [on hold]

recently i wrote an assignment in one of the questions i got two different answers for the same question by considering a straight line motion The question was somewhat like this THIS IS A HOMEWORK ...
-2
votes
1answer
85 views

How to derive this formula? [on hold]

as far as i know the range of an obliquely projected body which is projected with a velocity of u with some angle $\theta$ with the horizontal under the action of gravity is R=$u^2sin2\theta$/g by ...
0
votes
0answers
27 views

Deriving the Laguerre–Gaussian equation [closed]

How does one derive the Laguerre–Gaussian equation? $$ x\frac{d^2y}{dx^2}+\left(1-x\right)\frac{dy}{dx}+ny=0 $$
1
vote
1answer
27 views

The dimensional formula of distance travelled in $n$th second

I read that the dimensional formula of distance traveled in $n^{th}$ second is same as that of velocity. Okay, the formula for the distance traveled in $n^{th}$ second is $s_t= u+\frac{a}{2}(2t-1)$ ...
0
votes
1answer
36 views

How to find the final momenta of these objects? [on hold]

Suppose two objects collide head on, where initially object 1 (mass $m_1$) is moving and object 2 (mass $m_2$) is stationary. Now assume that they have the same mass, so $m_1 = m_2$. Which ...
1
vote
0answers
41 views

Defining axes for conservation of energy [closed]

Problem: A bungee-cord jumper is on a bridge that is $y_1$ above water level $y_2$. The bungee cord obeys Hooke's law with spring constant $k$ and has a relaxed length $L$ The jumper stops before ...
2
votes
4answers
69 views

Is work done by how much velocity is changed or how much displacement is done?

A sailboat is moving at a constant velocity. Is work being done by a net external force acting on the boat? The answer key is "No" according to the work energy theorem about work is done when ...
-1
votes
0answers
19 views

Solve the given differential equation by using Green's function method [migrated]

I am really struggling with the concept and handling of the Green's function. I have to solve the given differential equation using Green's function method $$\frac{d^{2}y}{dx^{2}}+k^{2}y=\delta ...
0
votes
0answers
13 views

How much inductance and capacitance generate in copper strip? [closed]

I have 60m long copper strip and cross-section area of 25mm x 3mm. and also it has some 90 degree turn after 10m distance. So, How much inductance and capacitance will be generated in strip.? and we ...
1
vote
0answers
247 views

Fourier Transform of Poisson Equation [migrated]

While trying to solve the Poisson Equation by using Green's Function I have to Fourier transform the equation i.e $$-\nabla^{2}\phi(r)=\rho(r).$$ In the book after Fourier transform, the solution ...
1
vote
1answer
72 views

Help with ideal gas law manipulation

Equation 1 represents an improvement over the intial assumption of constant mass velocity (i.e., $\rho v=\rho_o v_o$). We can now improve Eqn. (2) to get to Eqn. (3). My question is: what are the ...
-1
votes
3answers
70 views

Projectile Motion with air Resistance - Adjust only the Angle to hit a target

OK, let me preface this by saying i am not a physics student, nor have i ever been. I am a software engineer working on a development degree. So this is homework but the assignment was just to create ...
3
votes
4answers
125 views

Calculate water flow rate through orifice

I'm not very good with fluid physics, and need some help. Imagine the following setup with water contained in-front of a wall with an opening on the bottom: How do I calculate the water flow $Q$?. ...
-3
votes
0answers
27 views

Electrostatics coloumb's Law [closed]

The force of repulsion between two point charges is F, when these are at a distance of 0.1 m apart. Now the point charges are replaced by spheres of radii 5cm having the same charge as that of point ...
-2
votes
1answer
20 views

Calculate the current in mA which will be flowing through the two resistors [closed]

Three resistors of 3,4 and 5 ohms are joined in parallel in an electric circuit. If a current of 150mA flows through the resistor of 4 ohms,then calculate the values of the current in mA which will be ...
3
votes
2answers
148 views

Error in Standard Textbook “An Introduction to Quantum Field Theory” of Peskin and Schroeder?

On page 191 there is a equation for $D$ given by $$D=x(k^2-m^2)+y(k'^2-m^2)+z(k-p)^2+(x+y+z)i\epsilon. \tag{6.43}$$ With $k'=k+q$ and the constraint $x+y+z=1$. Also $p^2=p'^2=m^2$ and maybe $q=p'-p$. ...