Hi,
I think I got it. I'm calculating the force associated with the pressure difference, not the force associated with the potential. These have different directions. Then, because
F_{elastic}=-\frac{dU}{dr} (hooke's law)
\Delta P A = \frac{dU}{dr}
Is that it?
When a rubber balloon of spherical shape with un-stretched radius 0 r is inflated to a sphere of radius r ( ≥ r0 ), the balloon surface contains extra elastic energy due to the stretching. In a simplistic theory, the elastic energy at constant temperature T can be expressed by U= 4\Pi...
When a capacitor discharges, the potential difference between its plates and the resistor's terminals is the same. Hence,
\frac{Q}{C}=R \frac{dq}{dt}
Solving this equation we get
q(t)= Q_{0} exp \frac{t}{RC}
Obviously, this isn't the solution. It is actually q(t)= Q_0 exp...
Consider a rotating disk on a uniform magnetic field. Faraday's law states that
\epsilon = - \frac{d\phi}{dt}
In this situation, \vec B is constant and the area of the disk is constant. Hence, the magnetic flux is constant and there should be no emf. What am I missing?
Hello Galileo,
Thanks for the answer. Unfortunately, I couldn´t follow it because I don´t know what a tensor is. I´m still a high school student. I guess I´ll just have to use it without knowing how to derive it. which is something I really hate.
Hi
I´m self-studying Alonso and Finn´s Mechanics and I have a question about this subject.
Let a body rotate about an arbitrary axis P having angular momentum \vec L .
Consider a referential with three perpendicular axes, X_{0} , Y_{0} , Z_{0} , which are also principal axes of...
An interesting thing about this discussion is that the conclusion seems unanimous (ethics needs axioms or else we can´t argue). I never heard anyone defending what I am defending I encounter suddenly a lot of people who agree with me. Have this in mind: no philosopher admits what we´ve been...
Hi Apeiron
One thing to keep in mind is that ethics isn´t science in any way: there´s no reality to test it against because we can´t verify moral facts (if they exist...)
It´s an interesting idea but that just isn´t what the word "ethics" means. You can judge actions according to that...
This topic is not about what makes us be pious and generous to one another. Evolution does explain why we act that way. But that´s not what this discussion is about.
I only wanted to point out that we can´t look at some deed and say "oh, that is morally correct" whithout turning to an ethical...
Hi Russ,
Not everyone accepts this axiom. For example, the apartheid society might have been stable but it doesn´t seem fair.
I don´t think any philosophers admit that ethics needs axioms. I don´t know any that do. They always try to prove everything but that can´t be done, since you...
Hello everybody,
An argument I´ve seen is that we should stop asking why when the answer is "because it brings to a more stable society,..."
As Kajahtava pointed out, why should it be that way? Ethics is not about determining which behaviours lead to a stable, strong society. It is not...
That´s it.
What I mean by ethics is not what people think is right but what actually is right. I´m not interested in what people think so I´m not interest in antropology.
My post was about philosophy, about what makes certain actions be right. I´m saying that if we keep asking why is...
In science, if we did that we would arrive to experience. Laws work because they make good predictions and that´s all there is to it. In Mathematics if we kept asking why we would arrive to axioms.
But what about ethics? It´s not based on axioms or experience. Then, what is it based on? If...