# Questions tagged [homework-and-exercises]

Applies to questions of primarily educational value - not only questions that arise from actual homework assignments, but any question where it is preferable to guide the asker to the answer rather than giving it away outright. Please READ THE GUIDANCE IN META before asking homework-like questions.

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### Can I arbitrarily pick which resistors I should calculate the equivalent resistance with?

Let's say I have some random complex circuit of resistors. Maybe something like: Now I wanna calculate the equivalent resistance of this whole circuit. Can I just randomly pick which resistors I ...
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### Fitting a curve to my data [closed]

I got some data of the I-V characteristics of a solar cell (diode) in the dark and I have been trying to fit the data with the standard equation: $$I = I_0(e^{qv/nkT} - 1)$$ The below table is my ...
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### How do charges arrange themselves at electrostatic equilibrum?

How do charges on conductors re-arrange themselves when they are placed next to other conductors? I understand how charges arrange themselves on the surface of conductors but I can't find an ...
1 vote
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### Calculation in the book Path Integrals by Kleinert

I've been reviewing some fundamental calculations for path integral and I came across a passage to which I cannot figure out how it is supposed to be done. On page 92, the author started off, by ...
1 vote
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### Is there a difference between 10kg weight exerting 98N force vs. a person pulling the string with 98N force? [closed]

My question is related to an AP Physics question (2.k acceleration of systems), which appears simple, but the premise of part 2 of the question is difficult to understand, hence asking the physics ...
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### Magnetic flux due to movement [closed]

How does the magnetic flux decrease in the example shown below if the rectangle moves down due to the gravitational force, and there is no friction. The surface $A$ of the rectangle nor the magnetic ...
36 views

### Work done by ladder on the boy and work done by boy on ladder [closed]

I was stuck in a question: In a children's park there is a slide which has a total length of $10 \,\mathrm m$ and a height of $8 \,\mathrm m$. Vertical ladder is provided to reach the top. A boy ...
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### Derivation of Air resistance using Conservation Of Energy [closed]

I have been asked to derive an expression for the air resistance that a car moving with a constant velocity faces. The variables are mass of car, velocity of car, mass of air, density of air, cross ...
31 views

### Propagator for radial force field?

The propagator $K(x,y;t)$ is well known for the (1D) harmonic oscillator: $$H = -\frac{\hbar^2}{2m}\frac{\partial^2}{\partial x^2} + \frac{m}{2}\omega^2 x^2$$ is there a simple closed form solution ...
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1 vote
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### The maximum air drag force doesn't coincide with the maximum velocity

I'm trying to decode my data from an experiment conducted today. We wanted to calculate the air drag acting on a pendulum. In order do to this, we first created a model for our frictional force F: ...
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1 vote
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### String action in light-cone coordinates

I am going through textbook Einstein Gravity in a Nutshell by A. Zee and I got mathematically stuck at page 147 where he is talking about the classical string action using light cone coordinates. ...
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### How to find the voltage across a resistor in a RCL circuit? [closed]

In the circuit below I am trying to find an expression for the voltage across $R2$. I have found an expression for the voltage across R1 which I have confirmed with a simulation, but I can't get it ...
1 vote
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### Person is in a lift and the lift is accelerating downwards [closed]

My interpretation of part (ii) is that as $F=ma$, and the lift is going downwards, therefore the weight of the person would be greater than its reaction force. So $W-R=ma$. And $R=W-ma$. So the answer ...
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### Finding the expectation value given an operator in the form of a matrix and wave vector? [closed]

I was wondering how one would find the expectation value $\langle \hat{S} \rangle$ where $\hat{S}$ is just any operator in the form a matrix, such as the identity matrix \$\begin{bmatrix} 1 & 0 \\ ...
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### Is the norm of the acceleration the same as the componentwise calculation of the acceleration? [closed]

I am using the following question as an example to base my conceptual question on: 4.00-kg object has a velocity of 3.00i m/s at one instant. Eight seconds later, its velocity has increased to (8.00i +...
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