Recent content by .Scott

All four props are spinning about the yaw axis. But their total angular momentum is very near zero. So, their total gyroscopic effect will be near zero. The intent of most of the rest of my discussion was to describe why it would need to be kept close to zero - and what the exceptions would be.

Your question: why does body frame angular velocity equal to precession angular velocity which i have seen in all articles? If I understand this correctly, you are saying that those articles are calculating the precession velocity of the quad-copter only on the angular velocity of the frame -...

I have seen tempered glass break a few times. In those cases, it kind of disintegrated into very small (less than 1cm) pieces within a second. But if you are looking for information about a specific circumstance, you should try to get that info from the manufacturer. There is no assurance that...

I saw it about 9 months ago

Generally, when submarines want to communicate , they want to communicate with something miles away - and they do it by sticking something above the water (an antenna on their sail or a tethered buoy) and using radio communications. A discussion of how water absorbs EM is available in...

Right now, 1 and 5 are shown. After the disk is rotated, either 10 and X will show or 10 and Y will show. But in both cases, the gap between 10 and the other (X or Y) will be the same as the gap between 1 and 5.

Galaxy NGC 3972 is about 65 million light-years away. So with a telescope ... But, no, not images of ancient forests.

As @PeterDonis has said, nothing fits the bill of what you are describing. Certainly a material can be affected by exposure to light - especially a long-term exposure to direct sunlight, and the change could even be retained for millions of years. But you would be underwhelmed by the...

I was in my bedroom with the laundry room one floor below. If the washing machine is unbalanced when it goes into the spin cycle, it can create a rumble that goes on and off similar what I was hearing - so I was trying to determine if that rumble really was coming from the laundry room. But it...

My household in Pelham, NH heard it but did not really feel it. We live directly over an aquifer with wetlands on most sides - so there would have been an amplifying effect I didn't recognize it (at the time) as a quake and tried to determined what direction it came from - without success. It...

I agree (with @hutchphd) . When theta is taken as 90 degrees, then "Sin0" is 1 and the calculation in the second-to-last statement (of @tremain74 ) is correct. But what is "Therefore I assumed Sin0 = 490/100." supposed to mean? Even if you are trying to force it to the answer provided (the...

A: A function f(X) is a continuous map between two topological spaces X and f(X) B: f(X) is connected C: X is connected If C and Not B, then Not A. So the original sentence is When A: Then B, if C. This can be rewritten: If A, then (if C then B) The contrapositive: If not (if C then B) then...

Your "relevant equation" does not match your problem description. Your equation is used for a situation where there is a horizontal component to the velocity of the object in free flight. But the problem you stated does not presume any horizontal motion - nor would it be affected by horizontal...

When I say "isn't very long-lasting", I am talking about minutes or maybe and hour or two before it becomes imperceptible. I have a small night light in my bathroom. It is on 24/7. That's all it would take.

Phosphorescent and Fluorescence are consistent with what you have described is common in many materials - including those used in house paints. But that would be my second guess. My first guess is that the sewer pipe stretched from floor to ceiling (or wall to wall) and that the entry from the...