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.
11
votes
1answer
556 views
Mechanics + Thermodynamics: Bouncing Ball
In preparation for an exam, I'm revisiting old exam questions. This one seems neat, but also quite complicated:
A soccer ball with Radius $R=11cm$ is inflated at a pressure of $P =9 \times 10^4 ...
8
votes
9answers
5k views
What's the core difference between the electric and magnetic forces?
I require only a simple answer. One sentence is enough... (It's for high school physics)
7
votes
3answers
139 views
Trace and adjoint representation of $SU(N)$
In the adjoint representation of $SU(N)$, the generators $t^a_G$ are chosen as
$$ (t^a_G)_{bc}=-if^{abc} $$
The following identity can be found in Taizo Muta's book "Foundations of Quantum ...
7
votes
1answer
245 views
One strategy in a snowball fight
Here's a common college physics problem:
One strategy in a snowball fight is to throw a first snowball at a
high angle over level ground. While your opponent is watching the
first one, you ...
7
votes
2answers
789 views
Transformation of angles in special relativity
My question is about the problem below
Depicted are two space ships (the USS Voyager and the USS Enterprise), each with velocity $v=c/2$ relative to the space station (Babylon 5).
At the exact ...
7
votes
2answers
265 views
Equivalence principle and radiation from falling particle
I am currently having a hard time solving a problem of GR from Lasenby's book.
I can't make it more clear than by quoting the exercise:
7.2 A charged object held stationary in a laboratory on the ...
6
votes
3answers
1k views
Charge density in concentric spheres
Question:
If there are two conducting spherical shells and the inner shell is grounded, what will be >the charge density in the inner shell if there is a charge Q placed on the outer shell?
...
6
votes
2answers
742 views
How do Leptons arise from Lambda decay?
I have a question for an assignment:
Use your understanding of the quark model of hadrons and the boson model of the weak nuclear interaction to explain how leptons can arise from lambda decay, ...
6
votes
2answers
226 views
Conservation of energy in a non-linear oscillator
I have a homework question about a "non-linear oscillator". I actually have an answer to this question, but the answer I get is stronger than what is needed according to the question. The question ...
6
votes
0answers
201 views
exponential potential $ \exp(|x|) $
For $a$ being positive what are the quantization conditions for an exponential potential?
$$ - \frac{d^{2}}{dx^{2}}y(x)+ ae^{|x|}y(x)=E_{n}y(x) $$
with boundary conditions $$ y(0)=0=y(\infty) $$
I ...
6
votes
0answers
211 views
Capacitance of this unusual capacitor
This capacitor is composed of two half spherical shelled conductors both with radius $r$. There is a very small space between the two parts seeing to that no charge will exchange between them.
...
5
votes
3answers
296 views
Why isn't average speed equal to displacement over time?
I'm in an introductory Physics course and I need help!
During a one-hour trip, a small boat travels 80.0km north and then travels 60.0km east. What is the boat's average speed during the one-hour ...
5
votes
2answers
5k views
What is the relationship between kinetic energy and momentum?
I can't seem to figure out the relationship between $E_k$ and $p$ or $F$.
I understand that the units are pretty different. But for example:
A bullet with a mass of 10.0g is moving at the speed of ...
5
votes
4answers
3k views
Derivation of self-inductance of a long wire
Currently I am stuck, trying to derive the self-inductance of a long wire. According to literature it should be
$$L=\frac{\mu_r\mu_0l}{8\pi}$$
and in literature its derived by looking at the energy ...
5
votes
3answers
203 views
experimental technique for measuring temperature of an ant
I am taking a course on thermodynamics. I have a question from my text(halliday & resnick,physics-1). They asked me to measure temperature of an ant or an insect or a small body,like a small ...
