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location San Mateo, CA
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visits member for 3 years, 7 months
seen 21 hours ago

Nov
25
answered Why is microwave better than visible light for point to point data communication?
Nov
19
comment Find the rotation frequency of cars tires when we do now the velocity?
What have you tried? Can you calculate the circumference of the tyres? Then you can get the rotation rate from the speed. Watch the units.
Nov
16
revised Fuel tank draining
correct typo
Nov
16
answered Fuel tank draining
Nov
14
comment How come Wifi signals can go through walls, and bodies, by kitchen-microwaves only penetrate a few centimeters through absorbing surfaces?
@user3237992: the difference is that microwave ovens and WiFi operate at essentially the same frequency, so changes in absorption due to frequency are off topic here. I believe they penetrate the same, but we care about WiFi penetration and we don't recognize that the oven microwaves penetrate just the same.
Nov
14
comment How come Wifi signals can go through walls, and bodies, by kitchen-microwaves only penetrate a few centimeters through absorbing surfaces?
@K7PEH: It looks like your comments are directed to OP, not to me. You can comment on the question for that.
Nov
13
comment How come Wifi signals can go through walls, and bodies, by kitchen-microwaves only penetrate a few centimeters through absorbing surfaces?
@K7PEH: I don't expect the attenuation is any different. I said that a few times. The oven wall provides enough attenuation that we don't care about the signal (just as power) any more, then attenuation through walls knocks it even lower.
Nov
13
comment How come Wifi signals can go through walls, and bodies, by kitchen-microwaves only penetrate a few centimeters through absorbing surfaces?
@K7PEH: That is (just about) the same frequency most WiFi operates at, so it is fair to expect the same attenuation.
Nov
13
comment How come Wifi signals can go through walls, and bodies, by kitchen-microwaves only penetrate a few centimeters through absorbing surfaces?
How do you know they don't go through a few centimeters of an object. My point is that they will be attenuated by the same factor by any object. We don't normally have any way to detect them and don't care that in fact they do pass through. They are at a level (even before the attenuation) judged to be safe. Yes, there are meters that can detect the oven signals, but we don't carry them around normally.
Nov
13
answered How come Wifi signals can go through walls, and bodies, by kitchen-microwaves only penetrate a few centimeters through absorbing surfaces?
Nov
13
reviewed Approve suggested edit on How come Wifi signals can go through walls, and bodies, by kitchen-microwaves only penetrate a few centimeters through absorbing surfaces?
Nov
13
comment Where does the force to stop a constant velocity object come from?
If the ball truly has a constant velocity it has to pass through the wall, because the wall cannot accelerate it and cannot apply any force. When it is slowing down it is accelerating. Constant velocity is a reasonable approximation when there is no large force acting on the object. For the ball, we ignore air friction. When the ball hits the wall, it no longer has constant velocity.
Nov
12
comment Solar vs lunar gravity: inverse square law
@garyp: I do. The question is asking for a simple calculation, but wanders in many ways off topic.
Nov
12
answered Why is the required tire pressure inversely proportional to the volume/size of the tire?
Nov
11
comment Where is the fine-structure constant in this list?
There is a note that $\alpha(m_Z)=\dfrac 1{4 \pi}\dfrac {g \cdot g'}{g^2+g'^2} \approx \dfrac 1{128}$ and that the unfamiliar value is because of the energy level.
Nov
11
answered Where is the fine-structure constant in this list?
Nov
11
answered Will the heat increases with the resistance?
Nov
8
comment How would one best dissipate or absorb shockwaves and pressure caused by an explosion within a confined space
Are you hoping to limit the damage from one explosion or many? In other words, does the material need to survive intact, or can it be damaged? The second provides more options.
Nov
8
comment How would one best dissipate or absorb shockwaves and pressure caused by an explosion within a confined space
I think it is hard to absorb the energy in phase transitions, but my first thought is acoustic impedance mismatches and foams are very good at that.
Nov
5
awarded  Nice Answer