Safety Definition and 287 Threads

I've recently bought an electric mattress pad for my girlfriend. It has 4 separate heating zones (body and feet) and 2 controllers with a 2 plugs (not grounded - standard 2 prong EU plug). We turned it on and finally enjoyed a already warm bed when going to bed. Only problem: once we turned...

From what distance does the diffuse radiation of a „hair removal laser“ cease to be a threat? I apologize for the peculiar question, but I'm curious about the following matter: I walked past the window of a hair removal studio about 50 meters away earlier, and I noticed repeated bright red...

I am thinking about the health aspects of home led lighting and whether it is possible to filter out the shorter wavelength light. I am not sure what manufacturers do in order to produce their 'warm light' bulbs. They claim a lower colour temperature but how are they achieving that?

TL;DR Summary: What would happen if a bolt of continuous lightning hit an enclosed saltwater space with someone swimming far below the surface? Hello! I'm actually asking this as a DM for a DnD campaign. One of my players trapped a bad guy within a large (30m/side) freestanding cube of...

Hi PF, I am new here. I'm trying to perform a risk assessment to enumerate, and then take steps to mitigate, the risks posed by building a fusor and performing nuclear fusion. The risks as I see it are: 1. Electrical hazards posed by the high voltage equipment 2. Potential fuel-air explosion...

I ran a gel on electrophoresis that had proteins that were radio-labeled with 35s methionine, and in the process of imaging the gel (after 36 hr exposure on phosphor screen) I accidentally grabbed it with my bare hand. I'm getting very mixed messages regarding whether this is okay or not. Thoughts?

I would like to show students the Magdeburg hemispheres and ask for two volunteers to try to separate the hemispheres. In doing so, however, I am concerned that if the students actually succeed, they may fly off to the back and possibly injure themselves. How would you avoid this - for example...

The recent spate of train derailments has put the spotlight on derailments and railroad safety in general. Railroads are generally a safe means of transporting cargo, including hazardous chemicals, and in fact railroads are safer than a decade or two ago. Yet, one catastrophic accident...

Aaronson went on leave to join OpenAI and study AI safety, and wrote a blog post on the topic. https://scottaaronson.blog/?m=202211 Maybe this could be a good jumping off point to discuss the topic in general.

I am now faced with a problem. Part of the circuit I'm making consists of a row of many parallel mosfets. Parallel as in the drains are all tied to a rail and the sources also. I wonder, if one of the mosfets goes bad for whatever reason , how could I be able to tell without physically taking...

Hi, this is my first time using the Physics Forums so please let me know if this question belongs somewhere else. I'm a senior undergraduate at a mid-size institution in the United States seeking to purse a PhD in High Energy Theoretical physics or Quantum Information/Computing. I'm aware these...

Greetings I need to identify the elements of the following safety cluches: we have three different clutches. I lready identified most of them exept for number 14 Any help would be appreciated ! thank you! 1- output shaft 2-friction surface 3-preloaded spring 4-nut 5- input shaft 6- output...

Hello all I recently bought a cabbing grinder machine from India and now recognize that the motor(1/2hp 230v~) doesn't have any safety label or certificate whatsoever. I know close to nothing about motors or electricity and ask myself if it is safe to use the machine. To be honest I don't even...

Hello, as you can see in the attached image I have an opamp driving a BJT transistor that controls the power through a isolated mosfet driver IC that drives 2 series (back to back) N fets performing the duty of a solid state amplifier output relay. Now my concern is this. In case the output to...

I like using polypropylene dishware e.g. spoon, and storage box. I can see that from its label sometimes the maximum temperature recommended is 110 degree C or 120 degree C but it usually doesn't go away from this range. By common sense, I will never heat the polypropylene dishware directly but...

On Feb 28th, the anti-vaccination group "Doctors for Covid Ethics" wrote a first open letter with questions to the European Medicines Agency (EMA) regarding safety concerns of mainly mRNA vaccines. They have the hypothesis, that the LNPs of an mRNA vaccine go partly from the injection site into...

Falsified vaccines are not uncommon, as far as I know. How do they know a vaccine is authentic at a vaccination site that has no laboratory?

Hey guys, brand new here but looks like I'm in the right place :D I've got an OTF knife (a.k.a. "out the front," where the blade ejects straight out from the handle) that is held in the closed position with 1 lb, 12 ounces of magnetic force. I.e, upon measuring it takes 1 lb, 12 oz. of finger...

This following video demonstrates just how far the automotive safety has come over the decades.

Hi, I need to work out the FOS for a 16mm diameter bolt with a force of 8KN exerted on it. I have already worked out: direct stress = 34.47mPa shear stress = 199mPa Information given: Ultimate Tensile stress = 500NM/m2 Ultimate Shear stress = 300MN/m2 The FOS calculation I have been given to...

Is a PC free from viruses when disconnected with internet?

SAFETY RECALL 3 Ton and 6 Ton Heavy Duty Steel Jack Stands item numbers 56371, 61196, and 61197 For certain units of the Pittsburgh Automotive 3 Ton and 6 Ton Heavy Duty Steel Jack Stands there is a potential, while under load and with a shift in weight, for the pawl to disengage from the...

I cannot find a source of uranium glass beads/wands for art making. It is mentioned online that one can make UV glass with a derivative of uranyl nitrate, UO2(NO3)2 . Does anyone know a source of uranyl nitrate, or raw glass material, and what are the minimum safety protocols, such as...

Hello, So we are designing a turbine. We have a shaft that receives 710W / 13.6NM / 500RPM from the runner and we are going to find a diameter with safety factor of 3. Take the following information regarding metal: Aluminium 6061 Tensile strength 115 MPa Yield strength 48 MPa Shear...

hello, I'm new to this forum and I'm looking for some much needed help/guidance as i have absolutely no idea on how to workout my assignment! any help would be much appreciated

As a general rule of thumb what do you guys think is an ideal minimum safety margin when designing something? I know that this is a very broad question and could vary depending on the situation (ie something on a static load may need a smaller margin than dynamic) and since I do not have a...

I have not read this paper yet, but Lubos Motl blogs about it here: "A serious critique of the real-world Asymptotic Safety program for quantum gravity". The points I would list in favor of asymptotic safety's significance and viability, may be found in this Physics Stack Exchange...

I want to build a safe Villard cascade voltage multiplier so that I can create sparks that I can touch without dying or being injured. Is it possible to do this? And if so how would you construct it (specifically what capacitors and rectifiers and power source would be used)? My second question...

The question also considered 99m-Tc which has a 6h of half-life. And 99Tc has about 2.2E5 years. My argue was, “the half life of 99Tc is greater than the lifespan of a person. So ionization energy that is released has minimal effect to the person compared to Tc-99m which decays (and releases...

The recent 737 tragedies have shown us, I think, a few pointers about automation of planes. Of course, investigation is ongoing but my understanding is that the input from a faulty angle-of-attack sensor and an automated system which the pilots couldn’t switch off contributed. Two worries here...

I've been a semi-pro photographer for a long, long time. I know the value of having a polarizing filter in my camera bag. I also wear polarized sunglasses for driving during the day. You can't beat 'em. I know some people who are complaining about these LED head lights from oncoming cars...

Hey, I just finished applying to some astronomy/astrophysics grad school programs with way less research on the schools done than I should have. I used this forum thread to apply to some safety schools. University of Michigan* University of Hawaii at Manoa Vanderbilt Ohio State UC Boulder...

Homework Statement FIGURE 2 shows an improved arrangement for separating water from the hydrocarbon liquid for the process in question 2. Two simple level control loops, LC, have been added to regulate flow control valves on a pumped system. Extra protection is also provided in the form of high...

My question is about the relative eye safety of infrared (##\lambda \gtrsim 1400 \ nm##) and ultraviolet (##\lambda \lesssim 300\ nm##) lasers. Both of these wavelengths are highly absorbed by the pre-retinal water content in the cornea, so they don't really penetrate into the retina. So one...

PROS AND CONS OF INSTALLING AN EOT CRANES IN A LIMITED SPACE FACTORY. Capacity of the crane is 10 TON, SPAN is 27.6 meter, 4x10 Ton Cranes for 125 meter bay. The space limit in the factory is 10.5 meters. There is a 9 meter steel post at the center of the factory (part of a machine). The crane...

https://www.physicsforums.com/insights/dont-fear-https://www.physicsforums.com/insights/dont-fear-crispr-new-gene-editing-technologies-wont-lead-designer-babies/-new-gene-editing-technologies-wont-lead-designer-babies/provides scientists with an easy way to introduce targeted genetic changes to...

Sabine Hossenfelder recently wrote about an old theory of quantum gravity due to Weinberg: asymptotically safe quantum gravity. Is anyone familiar with this idea? What I couldn't figure out from the article is whether asymptotic safety is an approach to making consistent quantum field theories...

I'm assessing criticality safety of a waste removal plan for a (theoretical) abandoned russian laboratory. In the laboratory plutonium was recovered from fuel rods. The room is mainly empty except for a dissolver, a sump below the dissolver and spilled metal chips on the floor. The dissolver...

Homework Statement a) If you were using a hands –on activity to verify your predictions and use measurements to determine the wavelength of the laser being used, describe any safety precautions you would have to take and sources of error that you might encounter. Be sure to explain how you...

So you know I've been wanting to ask this question for some time now. Everytime you hear about an aviation disaster it is usually a plane that has had some trouble either with technical stuff or less often due to pilot error or otherwise, but what I want to say with that is that a big commercial...

Hello all. I am buying a laser engraver for my business. The company I'm getting it from and the "industry" in general doesn't think I need safety glasses when operating it (most say cause the light isn't visible to the eye) . I don't personally feel safe with that assumption for my eyes or my...

Hello, Community college teacher here. I was instructed to employ a laser safety program in my intro physics lab. We mainly use Class II lasers that came with the PASCO Optics table and Laser Ray boxes. One of my adjunct faculty uses Purple and green laser pointers which is classified as Class...

Disclaimer: I forget the names of tools often for some reason so I will often describe the tool rather than say it's name My shop teacher recently told me one of our machines is 45 years old. If I recall correctly it is the planar (device used to flatten the faces of wood). How long do you...

Hi, I was looking for some information on how to safely handle a shaded-pole motor of the sort found inside electric can openers and plugged into the mains. I was not sure of the voltages present on the shaded pole coils in particular.

Homework Statement A Bolt is in single shear and is tightened so that it exerts a tension force of 60kN, the diameter of the bolt is 25mm and the shear loading is 40kN; Given that the tensile stress should not exceed 350N/mm2 and the maximum shear stress should be taken as 60% of the maximum...

Homework Statement Ok so I have been presented with a bolt which has shear and tension acting upon it. I have done my best to 'draw' and recreate the problem with the information provided. I am trying to figure out how, one would go about choosing which of the two safety factors should be used...

Homework Statement Hello. I am trying to work out, the tensile stress, shear stress, and factor of safety. I have these to apply to it. Tensile strength = 460MPa Shear Stress = 280MPa Bolt Diameter of 8mm Force of 9kN Angle (a) = 50 degrees. Homework Equations Diagram[/B] The Attempt at a...

Hi educators, This may sound dumb, but my physics lecture room is our lab as well and we spend long hours in class. We spend approximately 4 hours for lecture and other activities and 2 hours for labs. Currently, I have a strict rule that only drink is allowed during lecture and other...