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371123
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location New England (USA)
age 53
visits member for 1 year, 10 months
seen 5 hours ago

I have formal training in physics, but tend to approach it very intuitively; I prefer estimation over exact calculation, principles over details. I believe many problems can be solved by making a careful sketch. Label your axes, and don't use insignificant digits.

I visit this site in the hope of sharing my enthusiasm and occasional insights with others.


6h
comment What is the ratio of Poisson's number for air?
There is no "ratio of Poisson's number". Do you mean Poisson ratio? It is ALWAYS between -1 and +0.5!
6h
comment Rain measurement with wind blowing
Don't delete it - just fix it! It is mostly good - and you will get some positive rep if you edit (and tell me) ;-)
1d
comment Drift of Earth's orbit?
See How fast is the earth-sun distance changing - the answer seems to be "1.2 +- 3.2 cm / year" - in other words, within the measurement error, it is not changing. Other sources (see same link) claim Earth moves away by up to 15 cm/year.
1d
comment Number of significant figures
I think this answer is spot on. And good to see a high school teacher on this site! I am sure there are (many) others and I just haven't noticed...?
1d
comment Volumetric flow rate as a function of radius of pipe
Yes - as you show it the level of the liquid gives an indication of the flow rate (goes as square root of height). But combined with the orifice plate it would allow a certain amount of visualization. Hard to calibrate but that might not be needed...
1d
comment Volumetric flow rate as a function of radius of pipe
@MikeDunlavey - you make a good point. There is some confusion here between "orifice" and "pipe" and the equations are quite different. In a pipe, it is the losses that dominate the flow rate; in an orifice, the question is "how fast can we accelerate the liquid to get through the hole" - like people trying to get into a subway car at rush hour. Then the flow scales with area (so $r^2$ as needed) - and a bunch of other things, but if you keep those constant you do indeed get an $r^2$ relationship.
1d
revised Two charged rods placed along the x and y axis respectively
edited tags
1d
comment Two charged rods placed along the x and y axis respectively
I recommend that you draw a diagram. Calculate the field due to each of the rods, and take their vector sum. You already have the field for one rod... so you're almost there.
1d
reviewed Close How long does it take a magnet to lose its magnetization?
1d
reviewed Close Where does the majority of the mass of the usual matter come from?
1d
reviewed Leave Open Electric field of two infinitely long and thin, straight wires
1d
reviewed Leave Open Volumetric flow rate as a function of radius of pipe
1d
comment Volumetric flow rate as a function of radius of pipe
Are you saying you want to change the size of the opening, but you don't want the liquid to come out 16x faster when you make the opening 2x bigger? Indeed you would have to make a system that changes the height of the liquid (pressure) as a function of the size of the hole. This is possible in principle - but what application do you have in mind that you want to, in essence, change the normal laws of physics?
1d
reviewed Leave Open How can we calculate the standard deviation of multiple values with different uncertainties each?
1d
comment How can we calculate the standard deviation of multiple values with different uncertainties each?
The answer will depend on whether you believe that you are measuring the same value (badly) many times, or that you are sampling a population of values, and your measurement adds uncertainty. And whether would like to know the standard deviation of the underlying population, or your uncertainty in the mean of the values (your estimate of the mean of the sampled population). Can you clarify which it is? In either case, I do not believe this is a duplicate of the question John Rennie pointed to . And it might be better on the statistics.SE
1d
reviewed Close Are there any video lectures on Phenemenology of standard model and Beyond Standard model theories?
2d
answered How does angular momentum affect the trajectory of a projectile?
2d
comment Velocity of a car in circular circuit
Right. If you want the "average velocity" over the time that the car drove around half the track, you would get a different answer - but in this case, the instantaneous velocity is the "instantaneous" displacement over a very small amount of time.
2d
revised String wrapping around a motionless cylinder
formatted equation, fixed typos
2d
comment Can I launch an object into orbit using only a cannon?
See the calculations in answer to this earlier question - not an exact duplicate, but close