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Jan
18
comment If heat is energy, then why does cooling take energy when it should actually give energy?
@Min: For me it's easier to visualize that particular value in pounds per square foot or pounds per square meter. Anyone that prefers other units can convert as they like. That's what computers or calculators are for. However, grams per square meter is not a unit of pressure, so it's always wrong. If you want to stick to MKS units, use Newtons per square meter.
Dec
13
comment Confusion about two-force members
If that's what you want to know, then again, ask about that. Your question as it currently stands is all hung up about whether A-C is a "two force" member or not. Write the question properly about what the forces are at pin A or on member A-C, if that's what you really want to know. You also seem to be misreading the diagram, or at least jumping to a incorrect conclusion.
Dec
13
comment Confusion about two-force members
I though you weren't interested in the actual solution, but the semantics of "two force member". If you want help with the solution, ask about that.
Dec
13
comment Confusion about two-force members
It should be obvious that A-C only has two forces on it (other than gravity, since weights weren't given I'm assuming you're supposed to ignore this). It is in compression, so the pin at each end is pushing on the member in the direction of the other pin. Since A-C isn't accellerating, those two forces are equal and opposite. What's the problem?
Dec
13
comment Confusion about two-force members
I wouldn't get hung up on someone else's artificial classification of the problem. I hadn't hear the term "two force member" before, but what does that matter anyway? I don't know what the problem is asking for, but it is easily possible to solve for the forces on the pins, force on member A-C, force on the bottom support, etc. If you're stuck solving this problem, ask about that specifically.
Dec
2
comment Does the Nuclear reaction happen inside the fuel rods?
@james: Yes, what you say is more specific. I was deliberately trying to stay away from the details of moderators, hence "sortof convert".
Nov
18
comment Does the ring (in the picture) experience Lorentz force?
But that's only due to the many turns of the coil. Take a look at Maxwell's equations.
Nov
18
comment Does the ring (in the picture) experience Lorentz force?
Point 1 is misleading at best. A magnetic field is produce by moving charges. They don't need to be accelerating. A straight wire with steady current flowing thru it will have a magnetic field around it, proportional to the current, not the derivative of the current or anything else that would imply acceleration.
Nov
6
comment If heat is energy, then why does cooling take energy when it should actually give energy?
@user: Consider that here on the surface of the earth the atmosphere has a lot of pressure, over 2000 pounds per square foot or 23,000 pounds per square meter. So why can't you use it to push your car along the highway for free?
Oct
12
comment What instrument should I use to vary the power given to a heating element?
@Sara: There are various ways, but those are electrical engineering questions. This is the physics site.
Oct
12
comment The role of mass in the tablecloth trick
@bhaus: I expect with the lightweight plastic plate that air motion affects were significant. With more weight, boundary layer air affects will matter less.
Oct
12
comment What instrument should I use to vary the power given to a heating element?
@What: The OP specified power control, not temperature control, so temperature feedback wouldn't actually solve the problem. Agreed though that the question is thin on specifics. Maybe he does want temperature control, but for now I'm answering what was asked.
Oct
12
comment What instrument should I use to vary the power given to a heating element?
This is the PHYSICS site. Nothing practical here. You want practical, you need the ENGINEERING site.
Oct
12
comment The role of mass in the tablecloth trick
@Carl: Yes, and that's because the classical ridgid body friction is proportional to perpendicular force rule fails. With a napkin on a tablecloth, you have deformable rough surfaces at the macro level, which is nothing like rigid body friction. Dishes and silverware on a reasonably smooth table cloth approximate to rigid body friction well enough for practical purposes.
Sep
27
comment Which factors are stopping us from studying Titan?
Such a big universe, so little time.
Sep
25
comment How does an electric field come inside a conducting wire inside the circuit?
@mili: I'm not really sure what to add. A inner chunk of wire can only see the voltage immediately across it. For there to be a voltage across its outer edge, the wire material on the other side of that edge must be conducting, else there would be no voltage by Ohm's law. One layer has to conduct before the next layer has a voltage drop across it, which then causes it to conduct. In reality there aren't discrete layers, so it is actually a exponential decay of the full current propagating into the interior of the wire.
Sep
4
comment Can I electrify a pin by applying current in its base?
Closing because cross-posting is not appreciated: engineering.stackexchange.com/q/5296/624
Aug
2
comment Can a hybrid vehicle ever be more efficient than a hydrocarbon-only vehicle built with the same parts?
@Chris: I don't believe that most of the energy goes into brakes, at least not for anything other than stop-and-go city driving. Regenerative breaking and shutting down the engine instead of idling certainly help, and hybrids do them for that reason. However, none of these explain why hybrids get such good milage on the highway. Even hybrids like the Toyota Prius and the Honda Civis Hybrid still do better on the highway than in city driving.
Jul
28
comment Why it is colder in mountains, at high altitudes?
Whoever downvoted this, it would be useful to know what you think is incorrect, misleading, or badly written.
Jul
25
comment Is all of the energy dissipated in a magnetic core in the form of heat and can any of it be recovered?
The first half of your first sentence is the only thing that makes sense here. It's not clear, but the rest of the hand waving is about a perpetual motion machine at best, or more "magnetic energy" nonsense at worst.