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Dec
7
comment Fluid Dynamics - How does air behave out a window?
If air comes in, some other air has to go out, or vice versa. It's not just one-way. (And quit smoking!)
Dec
2
comment Lift provided to an aeroplane
Aviation is over a century old, and it is very well understood. In spite of that, it's amazing how many people have been taught things that are wrong. Bernoulli's principle is not in conflict with Newton, in fact it is derived from conservation of momentum. Take a look at aerobatic planes with symmetric airfoils. They can fly inverted as easily as upright. The crucial variable is the angle of attack, which creates the downwash circulation. Asymmetric airfoils are nothing more than an optimization for non-aerobatic flight.
Dec
2
comment How to calculate the time it takes water to travel 100'
It sounds like the examiner is trying to see if you are confused by things that don't matter. I used to do that too. It's a good way to tell if you understand.
Dec
2
comment How much effect does wind have on cooling an object?
And various small airplane engines.
Dec
1
comment What forces are applied as a car exits a curve with constant speed?
+1 I would only add that in a car it takes a certain amount of time to move the steering wheel when transitioning from straight line to circular arc and back. In that time, the car is actually traveling in a spiral, so modern highways and railways all have spiral segments leading into and out of curves. (I programmed those on a 360 model 40!)
Nov
30
comment Kinetic energy of fluid + collision
@Tonylb1: Suppose have a stack of two 1kg boxes piled up. You grab the bottom box and lift the stack. How much force does it take? 2kg, right? Did the top box touch your hand? No. You lifted it through the bottom box. Gasses are the same way. Molecule A bounces off the surface. Then it bounces off B, then back, etc. Check out Newton's cradle.
Nov
30
comment Why on a frictionless incline, a rolling object reaches the bottom slower than an non-rolling object?
@Doeser: Smooth is one thing. Frictionless is another. If the slope is covered with grease, you won't get much rotation, it will all be sliding. Maybe you need to decide what your question is.
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.