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location San Mateo, CA
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visits member for 3 years, 4 months
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answered How can metal objects become electrically charged, if current flow means that an equal number of electrons enter/leave the object?
Aug
24
revised How can Excel be used to model the flight of a rocket?
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Aug
24
comment The thermodynamics of heating water in a rigid container
The only ways you have to absorb heat are to increase the temperature of the system or to convert liquid to gas. Clearly increasing the temperature will increase the pressure of the gas. To increase the volume of liquid you have to have the thermal expansion of the liquid very high, the compressibility of the liquid low, and the heat of vaporization high. I admit I don't have a proof that there cannot be a liquid like this, but usually more will boil than the expansion.
Aug
24
answered How can Excel be used to model the flight of a rocket?
Aug
24
answered The thermodynamics of heating water in a rigid container
Aug
23
comment Quantum machanics powering by -2?
I'm sorry, but "we power by -2" doesn't mean anything. You need to be more specific in your question. Maybe the context would help (but I still can't understand the phrase).
Aug
21
awarded  Civic Duty
Aug
16
comment Does decreasing the length of the line between a harness and zip wire increase the velocity at which you travel?
If I had to guess, the long harnesses for customers go with trolleys that have more resistance in the wheels. It is not about the length of the line, but about making sure the customers don't arrive at the bottom with too much speed. The instructors have training and gloves so they can slow down when needed.
Aug
15
comment Heat transfer to a cube from one of the faces
With a heat flux of $10$ MW in a few cm everything will vaporize quickly.
Aug
15
comment efficiency of electric cars vs gas?
Your points are good. One counterpoint is that it is easier to control emissions from a few powerplants than from a million cars. These tradeoffs are hard. In your case, it depends on what the source of electricity is. In any case, you are not crazy.
Aug
14
reviewed Approve suggested edit on When a star becomes a black hole, does its gravitational field strength become stronger?
Aug
10
comment Is it possible to 3D print a mirror to create a high quality telescope?
If you can print a thermally stable material, the stairsteps may be unacceptable, but you can be very close to the desired contour. It would be a very good start for some polishing.
Aug
10
answered How fast can fire spread?
Aug
8
answered Why does this model fall apart when angular velocity is small?
Aug
8
comment Why does this model fall apart when angular velocity is small?
If you show your derivation, it would be easier to comment. It can't be friction-there isn't any. You may have a small angle approximation you are using. It seems like $r$ should go smoothly to $0$ with $\omega$
Aug
6
comment Which is the most accurate way to model the fundamental atmospheric parameters of the Earth?
What data do you have? All these things change with time: the weather changes. If you want accuracy, you need current observations.
Aug
5
comment Where does the number “380,000 years for electrons to be trapped in orbits around nuclei” come from?
@ratchetfreak: A "short while" after the big bang time is well defined. Unless you think the "short while" is significant compared to 380,000 years, it can be ignored for this purpose.
Aug
3
comment Normal modes of the 2D double pendulum
If it is a normal mode the amplitude of every point should decrease steadily and smoothly. If it is not a normal mode, some amplitudes will increase as energy flows around. Think about the coupled pendulum. If you measure the location of one pendulum and start by exciting just one, the observed amplitude goes from 0 to max to 0 to max ... If you excite a normal mode, the amplitude of a pendulum just decreases smoothly due to friction
Aug
3
answered Normal modes of the 2D double pendulum
Aug
2
comment Does it take a lot of energy to heat metals up?
Metals tend to be good heat conductors. When you touch one, the heat from your fingers is conducted away, which is why they feel cold. When you touch an insulator, like a coffee cup, you quickly warm up the small volume around your fingers, so it doesn't feel cold. That may be what you are thinking.