# Search results

1. ### Power in terms of work and energy

I'm sorry if I sounded very ambiguous. But I think I got it now. I'm so hung up with the equation W=- \Delta U . See, the derivation for the energy associated with capacitors goes somewhere like this: Q=CV and let the lower case v and q be the any finite charge and voltage during the charging...
2. ### Power in terms of work and energy

Opps, yeah, I meant energy when I wrote 'U'. Anyways, I wonder if I can suggest that we look at it in the context of electromagnetism. Let's say I have a wire that has an increasing current in it, how exactly is the energy changing? Is it because of the changing potentials? Actually, I tried to...
3. ### Power in terms of work and energy

@nasu: I guess it's both, I want to know if dU/dt is equivalent to dW/dt in general,and what is the actual general definition of power?
4. ### Power in terms of work and energy

Is power a quantity defined by: \frac{dU}{dt} and \frac{dW}{dt} Is it just defined to be it, or can it be derived in terms of the other (I mean, dU/dt in terms of dW/dt and vice versa)? I now there's physical motivation to it, but sometimes I just can't help trying to ponder how these equations...
5. ### Plane's wings and Bernoulli's equation

Wow, my question seems to have spawned a lot of answers and an interesting discussion (though, most of those are all over my head for now). All I want to know is that why do we omit \rho g \Delta y when we calculate the pressure on the wings. Yes, the question plane question I've been...
6. ### Plane's wings and Bernoulli's equation

It's just a simple question about the pressure under and over the plane's wing problem that I'm trying to answer. Well, actually I've already answered it, but one just keeps bugging me. Why don't we consider the difference in altitude of the lower and upper points of the fluid (air) when we use...
7. ### Fluid Mechanics, Depth, Pressure

Thanks, I haven't read about buoyant force in depth yet, it's a good thing I've got some idea.
8. ### Fluid Mechanics, Depth, Pressure

Sorry, what actually goes through my mind is this: Not considering dy, Fnet = Ap(y)-w-Ap(y) = ma *Well, because I thought at both top and bottom A there is that same pressure p, we just got an additional pressure done by w. I kind of get it now though, if we solve for the net force on the...
9. ### Fluid Mechanics, Depth, Pressure

Sorry, what actually goes through my mind is this: Not considering dy, Fnet = Ap(y)-w-Ap(y) = ma *Well, because I thought at both top and bottom A there is that same pressure p, we just got an additional pressure done by w. I kind of get it now though, if we solve for the net force on parallel...
10. ### Fluid Mechanics, Depth, Pressure

Thanks, I thought no one would reply since my post was kinda messy. So the pressure really is different at differing altitudes, but I thought that was caused by considering the force done by the gravity I.e. the weight. Since there is weight then it gives a downward pressure at the top surface...
11. ### Fluid Mechanics, Depth, Pressure

I'm having a little problem with my book as I was reading about fluid mechanics. The book seems to have skipped a bit of some crucial part (at least for me) during the derivation for fluid pressure at certain depths (where the weight of the fluid is not neglected). Here, I'll try to reconstruct...
12. ### Constant velocity assumptions

Oh yeah, that was really silly. Thanks.
13. ### Constant velocity assumptions

It's been a while since I've done any work-energy questions, and I just noticed how vague some questions could be (or maybe I don't understand it that well). Anyway, suppose I have a box moving down an incline where the only forces acting on it are its weight, the normal force, and friction...