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Activity for Olin Lathrop‭

Type On... Excerpt Status Date
Comment Post #287068 The description is way too confusing to follow. Include a diagram, then we might have a chance to understand your setup. This question should be closed until then. Flagging for moderator attention.
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10 days ago
Comment Post #287053 Instead of bemoaning that your question isn't being answered, address the problems. You seem to have a clear idea in your mind, but all we can see is what you write. That is currently a lot of hand waving, and seems to contradict itself. Nobody can answer why your idea might or might not work if t...
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13 days ago
Comment Post #287039 C is a fixed point, so it can't be both at the center of the pool and on the surface of the water. The center is 1 m below the surface. F1 is a force, but is specified in units of mass. Even assuming 1g gravity, you can't apply any significant force to the surface of the water (ignoring surface ...
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15 days ago
Edit Post #287019 Post edited:
19 days ago
Edit Post #287019 Post edited:
19 days ago
Edit Post #287019 Initial revision 19 days ago
Answer A: If you're stopped and about to be hit from behind, should you brake or release the brake?
Basic answer It depends on what you care about. If you're primary concern is to minimize injury to the people in your car, then hold the brake firmly in ordinary low speed cases. This minimizes the motion of your car, which is what jerks around the passengers and causes injury. Actually the f...
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19 days ago
Edit Post #286936 Post edited:
30 days ago
Edit Post #286936 Post edited:
about 1 month ago
Edit Post #286936 Initial revision about 1 month ago
Answer A: How exactly do eddy currents slow down objects moving though a magnetic field
As the pendulum swings, it experiences a changing magnetic field from the externally fixed magnets. Any changing magnetic field causes eddy currents in a conductor. Since these conductors aren't perfect (the conductor has non-zero resistivity), energy will be dissipated by eddy currents. That ener...
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about 1 month ago
Comment Post #286906 Shouldn't that be "-" in first equation?
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about 2 months ago
Comment Post #286898 In addition, your "measurement value" is really hard to parse, to the point of being rude. -1 for the sloppiness.
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about 2 months ago
Edit Post #286873 Initial revision about 2 months ago
Answer A: System of ODEs models in physics
Pretty much any system where the state of one thing effects the rate of another, and the state of that other thing effects the rate of the first. Surely you can think of a few of those. One example is a capacitor and inductor wired in parallel. The voltage on the cap effects the rate of current ...
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about 2 months ago
Comment Post #286842 All charges are equal, so "sorting" them doesn't make any sense. Sort by what criteria?
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about 2 months ago
Edit Post #286811 Post edited:
2 months ago
Edit Post #286811 Initial revision 2 months ago
Answer A: Calculate inductance using laws of electromagnetism
Can we use other laws of electromagnetism to calculate the inductance of a piece of wire just like we used Gauss's law to calculate the capacitance of the 2 seperated conductors? Yes. The inductance of a length of wire is a function of the diameter of that wire and the material around it.
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2 months ago
Edit Post #286667 Initial revision 3 months ago
Answer A: Why can these Single Vision lenses slow myopia for kids, but not adults?
Why can these Single Vision lenses slow myopia for kids, but not adults? Kids' eyeballs are still growing, so there is opportunity to steer them into growing to a less myopic final result.
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3 months ago
Edit Post #286666 Initial revision 3 months ago
Answer A: What should this community's policy on "explain like I'm five" and similar statements be?
This site is not for five year olds. We are not kindergarten teachers. Asking a bunch of volunteers on the internet to explain physics to a five year old is a waste of time. Explanations at that level are out there and widely available. Imagine if we actually did answer appropriately for a fi...
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3 months ago
Edit Post #286646 Post edited:
3 months ago
Edit Post #286646 Initial revision 3 months ago
Answer A: Optically, why are circular eyeglasses lenses better than rectangular?
All refractive lenses are approximations of the ideal. This is particularly the case of single-element lenses such as in eyeglasses. It so happens that the centers of such lenses are closer approximations to the ideal than points further from the center. Put another way, it's easier to make good...
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3 months ago
Comment Post #286404 Canina already mentioned the speeds, but also consider how long it would take to get to those speeds. To prevent squishing your cosmonaut, you probably want to keep long term acceleration to 1 g. At that rate, it takes about 6 months just to get to ½c, at which time dilation is still very sm...
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5 months ago
Edit Post #286316 Initial revision 5 months ago
Answer A: Why can someone observe light, even when the light fails to illume that someone?
The light shines on everything in an unblocked direct line from the light source. This light is quite bright, so can be seen by human eyes all the way out to the horizon (until the curvature of the earth ends up blocking the direct line). It seems you are confused about the amount of light needed...
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5 months ago
Edit Post #286315 Initial revision 5 months ago
Answer A: Why do markers reflect light, even when the light source fails to illumine the space between the source and markers?
It counters intuition that although a light fails to illumine the area between the source and the target, the light can still illumine SOLELY the target! The light is illuminating everything. The photons don't magically disintegrate some fixed distance from the light source. The illumination get...
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5 months ago
Comment Post #285323 -1 for the many undefined variables. Ping me when fixed and I'll undo the downvote.
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7 months ago
Comment Post #285193 You have posted a lot of questions here without defining what your variables mean. The E=mc<sup>2</sup> equation is well known enough that most people probably understand that E is energy, m is mass, and c is the speed of light. However, you don't define terms in more obscure equations either. Wha...
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8 months ago
Edit Post #285862 Initial revision 8 months ago
Answer A: Calculating Surface temperatures of a thermal insulator
The "R value" of insulation is its thermal resistance. It tells you how much of a temperature difference is required to transfer a certain amount of heat power per unit area. The R-value you see on insulation in stores, at least here in North America, is in some arcane units, like &deg;F per BTU pe...
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8 months ago
Edit Post #285704 Initial revision 8 months ago
Answer A: Conductivity with angle of light
We don't know the details of your setup, but most likely there was a partially reflective surface over the actual photoresistor. The photoresistor itself may also be partially reflective. A higher fraction of the light is reflected off such surfaces at low angles. That means less of the light is...
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8 months ago
Edit Post #285609 Post edited:
9 months ago
Edit Post #285609 Initial revision 9 months ago
Answer A: Is that electron which jumps from one stationary state to another?
The electrons by themselves don't absorb or release this energy. They do that within the context of the atom they are within. The discrete energy levels available to electrons are only there due to them being lumped together in close proximity to the other electrons, protons, and neutrons that form...
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9 months ago
Edit Post #285586 Initial revision 9 months ago
Answer A: Why series springs behave like parallel? A comparison between parallel resistance and series spring.
The spring constant specifies force per compression distance. When you put multiple spring in series, the force on each spring is the same, which is also the overall force on the combined spring. The forces don't add. However, the displacements do add. If you have three springs in series with...
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9 months ago
Edit Post #285299 Post edited:
10 months ago
Edit Post #285299 Initial revision 10 months ago
Answer A: Are lamps, with blistering light bulbs exposed and facing down on the user, dangersome?
I'd say it's not the best design. Maybe that's why they discontinued it. However, there are also advantages. Cooling will be a little easier without a cover. But the real advantage is price. Ultimately, it is up to the consumer how much they care about the lower price, versus the chance of a...
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10 months ago
Edit Post #285153 Initial revision 10 months ago
Answer A: Are there areas in the observable universe which surely cannot support life as we know them?
After 4 edits, it seems you are asking whether there are places in the universe where galaxies can form, but planets in those galaxies can't support life. It seems you want life to be impossible due to some large-scale phenomenon that effects multiple galaxies, and not due to local conditions within...
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10 months ago
Comment Post #284890 I don't understand what we're looking at in the second picture. Is that part supposed to rotate? Where is the axel? That round thing doesn't seem to be a wheel, but what is it? Closeups are good, but remember that they require context to understand. That context is missing here.
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11 months ago
Comment Post #284890 How is it relevant that the unit is out of warranty, or that you can't afford a new one? What information is that supposed to convey for the purpose of explaining why the wheels are binding? I won't even guess because there seems to be something here I'm not getting.
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11 months ago
Edit Post #284870 Initial revision 11 months ago
Answer A: Calculate Center of Thrust
The center of thrust is effectively the weighted average of all the thrust locations. The weighting for each location is proportional to how much the thrust from that location contributes to the overall thrust. That is simply the dot product of the thrust from the specific location to the total thr...
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11 months ago
Edit Post #284739 Initial revision 11 months ago
Answer A: Who should the temporary moderators be?
We need marketing more than moderators There is so little activity here, even one person can easily handle the rare moderation tasks. If you just need to put a name in a slot, then I'm willing to do it, but I'm probably not the best person for the job. The real point is that you need to promot...
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11 months ago
Edit Post #284441 Post edited:
about 1 year ago
Edit Post #284441 Initial revision about 1 year ago
Answer A: Should I always write units in equation no matter if it looks like variable?
You are somewhat misquoting what I said. It would help if you provide a link to the comments you are asking about, but the issue was most likely about lack of units on numeric values, not variables. A number is dimensionless unless you explicitly provide units. A variable can be defined to have ...
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about 1 year ago
Edit Post #284431 Initial revision about 1 year ago
Answer A: What is Ether theory? (I think the book I read is misinterpreting Ether)
Back when what light is and how it propagates was poorly understood, people naturally related it to sound. Sound propagates thru a medium, like air. Light was therefore assumed to propagate thru a medium too. This hypothetical medium was referred to as the ether. While this line of reasoning is...
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about 1 year ago
Edit Post #283996 Post edited:
about 1 year ago
Edit Post #283996 Initial revision about 1 year ago
Answer A: Is it plausible to desire a "universal" calendar applicable everywhere in our universe?
It depends on what you want from your calendar. If you simply want a way to keep track of time, then you can base it on anything you like. The earth spinning on its axis, the moon orbiting the earth, and the earth orbiting the sun are irrelevant. However, most calendar systems were developed to ...
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about 1 year ago
Edit Post #283523 Initial revision about 1 year ago
Answer A: What happens if an electron collides with a proton?
While electrons have positive and protons have negative charge. They should collide and vanish, shouldn't they? No. They have other attributes than just being packets of charge. You have to consider mass too. That mass (or you can think of it as the equivalent energy) doesn't just disappear. S...
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about 1 year ago
Comment Post #283448 Actually your second equation is completely wrong (assuming the first is right) because the units don't match. Whatever m is, it has units of mass in the first equation, but is dimensionless in the second. We don't need to look any further to tell that the second equation clearly doesn't agree with...
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about 1 year ago
Edit Post #283395 Post edited:
about 1 year ago
Edit Post #283395 Initial revision about 1 year ago
Answer A: Why we can't find a particle accelerating unless there's some other particle accelerating somewhere else?
The third law says we will never find a particle accelerating unless there’s some other particle accelerating somewhere else. The other particle might be far away, as with the earth–sun system, but it’s always out there somewhere. This was probably embedded in more context. It seems the point he ...
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about 1 year ago
Edit Post #283304 Initial revision about 1 year ago
Answer A: Book suggestion category proposal
"Which xxx is best?" are poor questions for this Q&A site. When "best" can't be quantified, all you really get is a popularity contest. Another problem is when the available choices change over time. Let's not go there.
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about 1 year ago
Comment Post #283251 But 1: That's not how gravitational fields work, and 2: This is not stated in your question.
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about 1 year ago
Comment Post #283251 Too unclear and confusing. See comment.
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about 1 year ago
Comment Post #283251 Your question makes no sense because you can't suddenly "enter" your gravitational field at t=0. You show yourself that it exists in all space. And then what is supposed to happen to this test object? Is it supposed to just move inertially? This question is too confusing and poorly stated to be a...
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about 1 year ago
Edit Post #283266 Initial revision about 1 year ago
Answer A: Signal modeling as only digital, only analogue, or as both
This depends, of course, on what you are trying to achieve with the model. Remember that a model is a simplification for purpose of analysis, because the full physics is either too complicated or contains too many unknowns. By necessity, some real-world details are always left out of any model. ...
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about 1 year ago
Edit Post #283214 Post edited:
about 1 year ago
Edit Post #283214 Initial revision about 1 year ago
Answer A: What is the meaning that the universe is flat?
The universe could possibly wrap back onto itself, or it could be in infinite flat space. Imagine the difference between being on an infinite plane, or on the surface of a large sphere. In both of these 2D worlds, the universe would appear to extend infinitely in all directions. Yes, in the sphe...
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about 1 year ago
Edit Post #282730 Initial revision about 1 year ago
Answer A: Magnetic charges to solve interaction between 2 magnetic dipoles
Using imaginary magnetic charges (usually called magnetic monopoles) to solve for forces between two magnets doesn't make sense. Even if magnetic monopoles existed, what exactly do you envision doing with them to solve for the force between two magnets? Each magnet contributes to the magnetic fie...
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about 1 year ago
Edit Post #282186 Post edited:
Fixed grammar.
over 1 year ago
Edit Post #282193 Initial revision over 1 year ago
Answer A: Natural ways to acquire gravity for a colony on earth's moon
No, going deeper into the moon would reduce gravity. This is covered by the shell theorem of gravity, proved by Newton centuries ago. If you have an evenly-distributed mass shaped as a hollow sphere, then two things follow: Outside the shell, the gravity is the same as if the mass was all at t...
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over 1 year ago
Suggested Edit Post #282186 Suggested edit:
Fixed grammar.
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helpful over 1 year ago
Edit Post #281842 Post edited:
over 1 year ago
Edit Post #281842 Initial revision over 1 year ago
Answer A: decibel level of human hearing(human-auditory-range)
There seems to be some confusion about decibels here. "Decibel" stands for deci&sdot;Bel, meaning 10x of a Bel. A Bel is the log10 ratio of two powers, named for Alexander Graham Bell. Since a Bel is a large jump in human terms, the world has converged to largely use decibels, abbreviated "dB". ...
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over 1 year ago
Comment Post #281722 *"As driver for this ultra-fast expansion, cosmologists hypothesise a so-called inflaton field which drove the expansion, and which essentially disappeared at the end of inflation."* In other words, "We have no clue, so we're going to say magic happened.".
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over 1 year ago
Edit Post #281649 Post edited:
over 1 year ago
Edit Post #281649 Post edited:
over 1 year ago
Edit Post #281649 Post edited:
over 1 year ago
Edit Post #281649 Post edited:
over 1 year ago
Edit Post #281649 Post edited:
over 1 year ago
Edit Post #281649 Initial revision over 1 year ago
Answer A: Delta to Wye conversion
No, the answer can be seen by inspection in a few seconds, and it's not 2.8667. We don't just give answers to homework problems here, so I'll only make a few comments on the problem and your attempted solution: While this is on topic here, you would probably get better response on the Electrical ...
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over 1 year ago
Comment Post #281541 What's with the electric field strength in Newtons per square Coulomb? That's not the same as V/m as expected. Also, a uniform electric field will have a constant force on a point charge. Why do you expect a constant sideways force to have any effect on the pendulum frequency in the first place? ...
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over 1 year ago
Comment Post #281404 Due to entropy, the universe is worth less over time.
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over 1 year ago
Edit Post #281366 Initial revision over 1 year ago
Answer A: If planet 9 exists, is it correct to say that it is a "dark planet"?
Planet 9 would certainly be "dim", but whether it would be dark according you your definition is impossible to say. Planet 9 needs to be smaller or further away than Pluto, otherwise its gravitational effect would have been noticed more clearly by now. This means it probably reflects less light t...
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over 1 year ago
Comment Post #281359 The extra information you supplied about "dark planet" belongs in your question, not buried in a comment.
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over 1 year ago
Comment Post #281359 You need to define "dark planet".
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over 1 year ago
Comment Post #281321 Do the math! You need to melt a lot more than a liter or two of ice to have an appreciable cooling effect on a whole apartment.
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over 1 year ago
Edit Post #281296 Post edited:
over 1 year ago
Edit Post #281296 Initial revision over 1 year ago
Answer A: Does folding glasses increase the probability of separating at the hinge?
It depends on what the failure was. Working the hinge could possibly make the little screw come loose quicker. This is the screw that acts as the shaft of the hinge. If the hinge actually broke, then excessive repeated stress is probably the cause. This is more likely to come from too much fo...
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over 1 year ago
Comment Post #281290 All your pictures show the *right* hinge coming apart.
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over 1 year ago
Edit Post #281181 Initial revision over 1 year ago
Answer A: How dangerous is mounting and firing a gun on another human's body part?
This looks like something the soldiers are being trained to do, or were trained to do. This means procedures were likely worked out that mitigate most bad effects most of the time. The top picture in particular looks like a training exercise, and both soldiers are wearing obvious hearing protection...
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over 1 year ago
Comment Post #280987 *"What cleaning method is better?"* obviously depends on what is being cleaned (size, sensitivity to abrasion, sensitivity to cleaning chemicals, smooth/rough, accessibility, etc), the expected dirt to be removed (dust, grease, biological, etc), how clean it needs to be, for what purpose, etc. This ...
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over 1 year ago
Comment Post #280944 Does a meniscus really have a constant radius of curvature?
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over 1 year ago
Comment Post #280916 @dmckee: Higher index of refraction allows for less thickness change to get the same diopter. For negative diopter, the lens will be thin in the middle and thick on the outside. -7 is extreme (to the point where I wonder if it is correct), so the edges of the lenses will be significantly thicker th...
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over 1 year ago
Edit Post #280922 Initial revision over 1 year ago
Answer A: Why would a 1.74 index lens be more prone to chip and be less resilient than 1.67?
To be optically equivalent, the lens made from lower index of refraction material needs to be thicker. My guess is that your optician thinks the metal grooved frames you want won't work well with the outer thickness of the lenses. Note that he's not saying 1.74 index is bad, but just that it's so...
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over 1 year ago
Comment Post #280732 The OP had clearly done absolutely no research, and made several false statements in his question. It's OK to be ignorant, but not OK to be stupid. If you really want to get an answer, then you shouldn't be lecturing as part of the question. A kick in the butt is useful for these kinds of situatio...
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over 1 year ago
Edit Post #280719 Post edited:
over 1 year ago
Edit Post #280719 Initial revision over 1 year ago
Answer A: Would we need Alternating Current if superconducting wires existed?
The major advantage of Alternating Current is that it can be transmitted to large distances without significant losses, which is not possible in Direct Current. This is incorrect Answering the rest of your question is pointless since it is based on a false premise. Instead, I'll elaborate why ...
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over 1 year ago
Comment Post #280486 Get the proper lamp for the light pattern you want.
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over 1 year ago