FizzKicks
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Doubt in a property of Laplace equation
19 votes

The issue is that you have applied a 3-dimensional concept (i.e. Laplace's equation and potential falling with $\frac{1}{r}$) to a 1 dimensional boundary I think. The only solution to Laplace's ...

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Can acceleration depend linearly on velocity?
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18 votes

Yes, air resistance at low velocities is one such example, but I'm sure that there are others. For an object moving at a suitably low velocity, the drag on the object is given by $$\vec{F} = - b \vec{...

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Similarity between electromagnetic waves $E/B=c$ compared with the equality between Lorentz force and electric force
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3 votes

The first boxed equation refers specifically to the ratio of the magnitudes of electric to magnetic fields in a electromagnetic wave propagating through a vacuum. The second equation refers to the ...

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What are the principal applications of linear algebra in theoretical physics?
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3 votes

There are lots of cases outside of QM where linear algebra can be of great use. If we have a coupled oscillator, then the equations of motion can be solved using linear algebra with ease. In special ...

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Is it possible to block a gravitational wave?
2 votes

Interesting thought about using gravitational waves to communicate - I find it to be exceedingly unlikely, but I like the creativity. As to whether or not they could be blocked, not really - when ...

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Examples of solvable simple systems in relativistic mechanics
2 votes

Probably the simplest one is the case of an object which experiences an acceleration which is constant in its own frame i.e. a rocket in deep space, where the change in mass of the rocket due to fuel ...

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Confused about definition of three dimensional position operator in QM
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2 votes

This is quite an odd way to introduce the position operator, I have to admit. Both definitions you have used are correct, they're just used in different ways in quantum mechanics. In the the first ...

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Air drag on a projectile
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2 votes

Your suggestion is correct in someways but incorrect in others. A better representation of the drag force would be $$\vec{F}_{drag} = \alpha (V_x(t)\space\vec{i}\space +\space V_y(t)\space\vec{j})$$ ...

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Should the implied uncertainty of a measurement be ±½ or ±1 of its least significant figure?
2 votes

I think you're grossly over-complicating things here. I've listed the convention below for most high-school and undergraduate level treatment of uncertainty. $$\\$$ When a measurement is made with an ...

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Calculate the effective refractive index from group index
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1 votes

We can rewrite the differential equation as: $$\frac{1}{\lambda}\frac{dn_{eff}}{d\lambda}-\frac{n_{eff}}{\lambda^2}=\frac{d}{d\lambda}\left(\frac{n_{eff}}{\lambda}\right)=-\frac{n_g}{\lambda^2}$$ So$$\...

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Mass change of a black hole during the Penrose process
1 votes

I think I have solved this by realising that we can define the energy by the invariant $E^{(B)} = \textbf{u}_{obs} \cdot \textbf{p}^{(B)}$, where $\textbf{u}_{obs}$ is the observer who is measuring ...

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Calculate distance based on - Resistance - Acceleration - Time - Initial Velocity
1 votes

So for these kind of problems, I'm no programmer by any means, but the easiest way to proceed seems to be to use Newton's second law, $F = ma$, with $F = Force$, $m = mass, $ and $a = acceleration$. ...

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Is it possible for two observers to observe different wavefunctions for one electron?
1 votes

I will confess that this I am not certain on this, as this is a quite odd question. but I have formulated what seems like a very reasonable answer. Also the very first thing to mention is that one ...

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Can length contraction actually be seen in the real world? Light from different parts of an object will reach an observer at different times
1 votes

Okay so this image is a bit daunting, and by no means should you discount Terrell Rotation (it's one of the most interesting parts of relativity in my opinion), but this should help give an idea of ...

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What is the rank of the quadrupole moment tensor in QM and nuclear physics?
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1 votes

Remember the notation; what you have written above it the expectation value of the operator, i.e. $$⟨\psi|Q|\psi⟩ = ⟨Q⟩ $$ is clearly a scalar, but we can see from the operation of Q that it is a rank ...

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Torque due to applied force on a cord vs. torque due to gravity acting on weight attached to the cord
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1 votes

You are forgetting that the weight attached will gain kinetic energy as well, taking away from the energy that the cylinder can have for rotation, and hence lowering the final angular velocity.

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Difference between different radial and centripetal accelerations:(Doubt)
1 votes

If we consider only the radial component in the case when $\dot{\theta} = 0$, then it becomes clear that $\ddot{r}$ is a radial acceleration, i.e. since the angular component of velocity is $0$, the ...

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How to prove that path of a charged particle in a uniform magnetic field is circular or helical?
1 votes

I've put down an answer that should help you but doesn't dive deeply into the mathematics, if you're feeling confident I would suggest trying to solve it using equations of motion and coupled ...

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Do light particles have thrust?
0 votes

One of the weird things about light is that in vacuum it always moves at the speed of light through space-time, which means that there is nothing we could do to make it go faster. So if you were to ...

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Mechanism of Relativistic Momentum
0 votes

I think what you are looking for is an understanding of 4-force, that is the vector which describes force in relativity. Without getting into the details (which are easily accessible by a google ...

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Influence of object mass on impact force
0 votes

I don't see what is necessarily wrong with leaving it in the form with $v_f$ and concluding that it is proportional to $m^\frac{1}{2}$, but nonetheless we can at least come up with some physical ...

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Plucked string at $t=0$ and its Fourier decomposition
0 votes

We have the general solution $$y(x,t) = \sum_{n=0}^\infty sin(\frac{n\pi x}{a})(b_ncos(\frac{n\pi ct}{a})+c_nsin(\frac{n\pi ct}{a}))$$ For a string constrained to $y(0,t) = y(a,t) = 0$. We can then ...

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