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Nov
30
comment Why on a frictionless incline, a rolling object reaches the bottom slower than an non-rolling object?
@Doeser: First go with intuitive understanding, then work it against the math. Suppose you have a Pinewood derby race. Then suppose you have a friction motor car and run it down the track. I hope you can see that the friction motor car will travel very slowly, because all the energy goes into its flywheel.
Nov
30
comment Why on a frictionless incline, a rolling object reaches the bottom slower than an non-rolling object?
@What: As Doeser admitted, the incline is not frictionless. I would edit the title, but I'll leave that to Doeser.
Nov
30
comment Kinetic energy of fluid + collision
@Tonylb1: Still, it's a fluid. Every molecule of the fluid doesn't have to bounce off the blade. Some do, and then the others bounce off them.
Nov
29
comment Why on a frictionless incline, a rolling object reaches the bottom slower than an non-rolling object?
I shouldn't use a comment to answer your question, but it's very simple. An object will roll down slower if part of its KE is rotational, rather than devoted to forward motion. After all, you can lift a bicycle wheel off the ground and spin it, so it has plenty of rotational KE, but zero translational KE.
Nov
29
comment Why on a frictionless incline, a rolling object reaches the bottom slower than an non-rolling object?
If the incline were frictionless, as your question says, the object would simply slide, not roll. Do you want to edit the title of the question?
Nov
26
comment How does Bernoulli's principle produce wing lift?
@tpg2114: You clearly know more about it than I do. I was just going by the Wikipedia summation. Maybe you can tell if Kurzweil is mistaken.
Nov
25
comment How does Bernoulli's principle produce wing lift?
I can suppose Kurzweil is talking about the Kutta condition which is "not yet fully settled" mathematically, but there is no doubt that it applies. It has to do with the question: why does the air not snap around the trailing edge of a wing and go to the upper surface? Wing lift fundamentally depends on this. To explain it requires viscosity.
Nov
25
comment How does Bernoulli's principle produce wing lift?
@tpg2114: equal transit gets it right?
Nov
25
comment How does Bernoulli's principle produce wing lift?
When Kurzweil says that, there must be more to what he is saying. As you've quoted it, it makes no sense. I'm trying to guess what he's referring to. Is it the reason behind the Kutta condition, for example?
Nov
25
comment Does the International Space Station always travels in the same path?
Nice explanation. There are also smaller orbit changes as they sometimes fire thrusters to dodge debris.
Nov
20
comment Turning Heat into Work
I think you're asking - Can you build a steam engine with a soda can? If you're clever, I imagine you could. Would it be useful? That's for you to decide. In any case, as @Kyle said, it's an engineering question.
Nov
17
comment How does a cyclist moves the center of mass of the cycle-cyclist system?
@user: I forgot to mention, there's another way to balance, by making use of angular moment of inertia, the way a high-wire walker uses a long balance beam. You can move your support angle (or your COM) by treating that beam as a level reference. So now I'm not so sure of my answer.
Nov
17
comment How does a cyclist moves the center of mass of the cycle-cyclist system?
@user: If you can do it once, you can do it again. Find a parking lot or something with long straight lines painted on the ground. Now see if you can ride your bike straight down the absolute center of that line for 100 yards or more. Answer me after you've tried it.
Nov
17
comment How does a cyclist moves the center of mass of the cycle-cyclist system?
@user: He does steer the front wheel. Try what I said.
Nov
17
comment How does a cyclist moves the center of mass of the cycle-cyclist system?
@user: You don't move your center of mass, you move your point of support. Try balancing anything: a baseball bat, ladder, broom. You do it by moving the point of support. Try riding your motorcycle and keeping the front wheel on a narrow line on the pavement so it can't go left or right. You can't do it for long.
Nov
13
comment In a circuit one light-second long, does it matter where in the circuit the switch is placed?
Can't you arrange the wire so that the inductance is zero? Then doesn't the question make sense?
Nov
7
comment How does inhalation work?
I still have my favorite physical law: Nature abhors a vacuum. It especially seems to apply to computers and software, and even to wallets :)
Nov
6
comment Calculating effective capacitance of a circuit
The problem with just giving the answer is the asker doesn't learn, and neither does anyone else.
Nov
3
comment What is Pressure Energy?
@TimKrul: No fluid is truly incompressible. If it were, the speed of sound in it would be c. Incompressibility only means it is quite stiff, in which case it can have high pressure, but not much pressure energy. i.e. d=0 in your equation.
Nov
1
comment Why is paper (or any tailless) airplane pitch stable?
@RoelSchroeven: We're basically in agreement. As John Denker points out, the term is decalage. The point is, there needs to be an upward pitch moment that increases with speed, counteracting the nose-heaviness. Civilian aircraft are built that way. Fighter jets with fly-by-wire are not. They sacrifice stability for maneuverability, but it takes a computer to fly them.