# 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.

15,912 questions
Filter by
Sorted by
Tagged with
1k views

### Shape of a rotating rope with one free-end [closed]

One end of a uniform rope (with total mass $M$) is fixed on the edge of a cylinder. The cylinder has a radius $R$ and rotates with angular velocity $\omega$. The axis is vertical in a gravitational ...
34 views

### “dielectric constant” or “electrical permittivity”?

What are the differences between "dielectric constant" and "electrical permittivity"? By searching on the net, I found permittivity = absolute permittivity, which is the measure of capacitance that ...
70 views

165 views

### Why is $x^n \psi^{(m)}(x)$ zero at infinity? [duplicate]

Prove: Product of any polynomial of $x$ with $\psi(x)$ or any of its derivatives goes to zero in the limit $x\to\pm\infty$. This comes from a footnote written by the professor in his quantum ...
34 views

### Why is this derivation of rotational kinetic energy wrong?

I was trying to derive the rotational kinetic energy of a solid sphere with radius $R$ using the following idea. Each infinitesimally small shell volume $4\pi r^2 \cdot dr$ at radius $r$ within the ...
47 views

### Charges redistribution in Conducting Plates

Lets Suppose there is Conducting plate X and charge Q is given to which means +Q/2 and +Q/2 on each side . Now lets suppose plate Y (uncharged at first) (exactly similar to plate X (area and material ...
41 views

### Pressure variation in liquids with varying densities [closed]

There is a question mentioned in my textbook which is given below Equal masses of three liquids are kept in 3 identical cylindrical vessels A, Band C . The densities are Da,Db and Dc with Da < ...
31 views

### Pressure at the bottom of the fluid (fluid mechanics) [closed]

There is a question given my book which is stated below The three vessels shown in figure have the the same base area. Equal volumes of a liquid are poured in the three vessels the force on the ...
38 views

### Calculating heat current through a spherical shell [closed]

I have a spherical shell with inner radius $a$ and outer radius $b>a$. There is a temperature difference of $\Delta T$ between the inner and outer shells. The thermal conductivity is $k$. The ...
45 views

### Having some tension about the Tension in Atwood's Machine

I was thinking about how the tension force is equal in a massless String. While the explanation that the String would accelerate crazy, crazy, crazy fast if there was an actual difference makes sense, ...
5k views

### Does friction always oppose motion?

Recently I had the following misconceptions: Static friction always opposes the motion of body. The force of friction cannot initiate motion in a body. Now I came to know that my understanding was ...
62 views

### Is this a valid solution for the underdamped wave equation?

The loss factor and the wave number are replaced by an expression depended by the damped frequency. Could the last expression be a valid solution for the underdamped wave equation when the initial ...