Explosion in a grain storage facility at the Société d’Exploitation Maritime Blayaise killed 11 people in nearby offices and injured one. The area of the sheet in appropriate significant figures and error is. Mines may also be sprayed with water to inhibit ignition. They are also commonly used by special effects artists, filmmakers, and pyrotechnicians, given their spectacular appearance and ability to be safely contained under certain carefully controlled conditions. (a) The size of an atom is much smaller than even the sharp tip of a pin. For example, a 1 kilogram (2.2 lb) sphere of a combustible material with a density of 1 g/cm3 would be about 12.4 centimetres (4.9 in) in diameter, and have a surface area of 0.048 square metres (0.52 sq ft). Knowing the volume of the drop and area of the film we can calculate the thickness of the film which will give us the size of oleic acid molecule. High-oxygen or pure oxygen environments are considered to be especially hazardous, as are strong oxidizing gases such as chlorine and fluorine. The number thus obtained is known as the magnitude […] To get fastest exam alerts and government job alerts in India, join our Telegram channel. In Kundt’s tube method, (a) particle in powder makes displacement according to the pressure of. It is characterised by severe itching (particularly at night), red spots, and may lead to a secondary infection. dict_files/eng_com.dic This class can parse, analyze words and interprets sentences. What will be the diameter of the earth (approximately in degrees) as seen from the moon? Many common materials which are known to burn can generate a dust explosion, such as coal and sawdust. The mean length of an object is 5 cm. Dust explosions can occur where any dispersed powdered combustible material is present in high-enough concentrations in the atmosphere or other oxidizing gaseous medium, such as pure oxygen. Here we have covered Important Questions on Units and Measurements for Class 11 Physics subject. (a) How many astronomical units (A.U.) Now 1 drop of this diluted solution is placed on water in a shallow trough. In this activity, students will run simulated tests of various metals in aqueous solutions to determine the relative reactivity of these metals. (a) The earth-moon distance is about 60 earth radius. Dusts have a very large surface area compared to their mass. (a) Why do we dissolve oleic acid in alcohol? Primary dust explosions may occur inside process equipment or similar enclosures, and are generally controlled by pressure relief through purpose-built ducting to the external atmosphere. Intense radiant heat from a fireball can ignite the surroundings, or cause severe skin burns in unprotected persons. Go Back to Physics Home Page Chemistry Maths Biology. The blast was felt for miles around and completely leveled the plant owned by the company. Much research has been carried out in Europe and elsewhere to understand how to control these dangers, but dust explosions still occur. Einstein’s mass – energy relation emerging out of his famous theory of relativity relates mass (m ) to energy ( E ) as E = mc. (e) What will be the volume of oleic acid in one drop of this solution? Thermobaric weapons utilize this principle by rapidly saturating an area with an easily combustible material and then igniting it to produce explosive force. Large terminal grain elevator in Kansas City, Originated in basement of elevator, during a cleanup period, and travelled up through the elevator shaft. [5] For example, in machining operations downstream of the AM build, excess powder liberated from porosities in the support structures can be exposed to sparks from the cutting interface. Then 1 mL of this solution is diluted to 20 mL by adding alcohol. However, if it were broken up into spherical dust particles 50 µm in diameter (about the size of flour particles) it would have a surface area of 120 square metres (1,300 sq ft). (d) The air inside this room contains more number of molecules than in one mole of air. You also get idea about the type of questions and method to answer in your Class 11th examination. It came up with all the anagrams that would fit a given set of words: this often ran to thousands or hundreds of thousands of anagrams, often pretty unintelligible. Occupational Health & Safety Information Service, UK. In the coal mining industry, a methane explosion can initiate a coal dust explosion, which can then engulf an entire mine pit. Powdered metals (such as aluminum, magnesium, and titanium) can form explosive suspensions in air, if finely divided. A gigantic explosion of flour dust destroyed a mill in Minnesota on May 2, 1878, killing 18 workers at the Washburn A Mill and another four in adjacent buildings. Write the relation between the distances and sizes of the sun and moon. If the unit of force is 100 N, unit of length is 10 m and unit of time is 100 s, what is the unit of mass in this system of units? "OSHA Fact Sheet: Hazard Alert: Combustible Dust Explosions", "Will My AM Part Explode? 5. Calculate the length of the arc of a circle of radius 31.0 cm which π/6 subtends an angle of at the centre. The dimensions of h are the same as that of. 1mL of this solution is diluted to 20mL by adding alcohol. b) With the help of lycopodium powder one can measure the area over which the oleic acid spreads as lycopodium powder clears the circular area when oleic acid is added. Below a certain value, the lower explosive limit (LEL), there is insufficient dust to support the combustion at the rate required for an explosion. Flying objects and debris can cause further damage. These weapons are the most powerful non-nuclear weapons in existence. This is the world's worst-ever coal-mining accident. 7. However, use of oxygen-free gases brings a risk of asphyxiation of the workers. (c) The mass of Jupiter is very large compared to that of the earth. A dust explosion is the rapid combustion of fine particles suspended in the air within an enclosed location. Now, lycopodium powder is sprinkled evenly over the film and its diameter is measured. [8] Similarly, if the fuel to air ratio increases above the upper explosive limit (UEL), there is insufficient oxidant to permit combustion to continue at the necessary rate. Typical explosive ranges in air are from few dozens grams/m3 for the minimum limit, to few kg/m3 for the maximum limit. Butterworth-Heinemann. Intense radiant heat has nothing to ignite here, Aftermath of explosion, with unburned flour on the ground, A dust explosion can cause major damage to structures, equipment, and personnel from violent overpressure or shockwave effects. Online Dictionaries: Definition of Options|Tips Options|Tips This can cause more deaths than the original explosion as well as hindering rescue attempts.[10][11]. Determining the minimum explosive concentration or maximum explosive concentration of dusts in air is difficult, and consulting different sources can lead to quite different results. Which of the following ratios express pressure? NCERT Exemplar Class 11 Physics is very important resource for students preparing for XI Board Examination. Determination of wavelength of laser light using semiconductor laser diffraction. Determination of Acceptance angle and Numerical Aperture using fiber optic cable. The particle size of the perchlorate is not as critical as that of the aluminium component, as much less energy is required to decompose the KClO 4 than is needed to melt … Based on observations, write the the oxidation-reduction half-reactions. The vernier scale of a travelling microscope has 50 divisions which coincide with 49 main scale divisions. Good housekeeping practices, such as eliminating build-up of combustible dust deposits that could be disturbed and lead to a secondary explosion, also help mitigate the problem. [7] Common sources of ignition include: However, it is often difficult to determine the exact source of ignition when investigating after an explosion. (b) A Jet plane moves with a speed greater than that of a super fast train. If rapid combustion occurs in a confined space, enormous overpressures can build up, causing major structural damage and flying debris. The solution spreads over the surface of water forming one molecule thick layer. [1]. In a tightly enclosed space, the sudden depletion of oxygen can cause asphyxiation. If each main scale division is 0.5 mm, calculate the minimum inaccuracy in the measurement of distance. and size when placed in a (a) magnetic field (b) alternating current (c) electric field ... Lycopodium powder can be used (d) All are correct. Best engineering control measures which can be found in the National Fire Protection Association (NFPA) Combustible Dust Standards[12] include: Dust clouds are a common source of explosions, causing an estimated 2,000 explosions annually in Europe. definition of - senses, usage, synonyms, thesaurus. As a precaution, incombustible stone dust may be spread along mine roadways, or stored in trays hanging from the roof, to dilute the coal dust stirred up by a shockwave to the point where it cannot burn. [5] Efforts are underway not only to build this knowledgebase within the industry but also to share it with local fire departments, who do periodic fire-safety inspections of businesses in their districts and who can expect to answer alarms at shops or plants where AM is now part of the production mix.[5]. Dust explosions may be classified as being either "primary" or "secondary" in nature. Some industries exclude oxygen from dust-raising processes, a precaution known as "inerting". This greatly-increased surface area allows the material to burn much faster, and the extremely small mass of each particle allows them to catch on fire with much less energy than the bulk material, as there is no heat loss to conduction within the material. Typically, normal atmospheric oxygen can be sufficient to support a dust explosion if the other necessary conditions are also present. In cases when fuel plays the role of a combustible material, the explosion is known as a fuel-air explosion. An artificial satellite is revolving around a planet of mass M and radius R, in a cir cular orbit of radius r. From Kepler’s Third law about the period of a satellite around a common central body, square of the period of revolution T is proportional to the cube of the radius of the orbit r. Show using dimensional analysis, that. Typically this uses nitrogen, carbon dioxide, or argon, which are incombustible gases which can displace oxygen. Which of the following pairs of physical quantities does not have same dimensional formula? Prompted mills throughout the country to install better ventilation systems to prevent dust build-up. If the spread of flame is at subsonic speed, the phenomenon is sometimes called a "deflagration", although looser usage calls both phenomena "explosions". Write the dimensional formula of (i) ω and (ii) k. Time for 20 oscillations of a pendulum is measured as t. A new system of units is proposed in which unit of mass is α kg, unit of length β m and unit of time γ s. How much will 5 J measure in this new system? 9. [2], There are five necessary conditions for a dust explosion:[3]. 6. If a row of “dominoes” gradually increases in height, investigate how the energy transfer takes place and determine any limitations to the size of the dominoes. Benzyl benzoate is one of the older preparations used to treat scabies. This is the SpellCHEX dictionary for online spell checking. Physics Class 11 Important Questions are very helpful to score high marks in board exams. Nelkon and Parkers A lvl physics Books for those who are going to be taking IGSCE and other equivalent Exams soon.I do not hold any copyright or anything.Just wanted to share the free material for those who are keen to learn Physics.All Rights Name the device used for measuring the mass of atoms and molecules. The volume of a liquid flowing out per second of a pipe of length l and radius r is written by a student as. Which of the following measurements is most accurate? (b) What is the role of lycopodium powder? The solution spreads over the surface of water forming one molecule thick layer. The distance of a galaxy is of the order of 10. Dust Explosions in the Process Industries (2nd ed.). Which of the following time measuring devices is most precise? (e) This is a correct statement. The solution came out a few months later and I immediately applied it on the Unix machine I had at work. 9. "Corn Starch Dust Explosion at General Foods Ltd, Banbury, Oxfordshire – 18th November 1981". Calculate the solid angle subtended by the periphery of an area of 1cm. [13] The table lists notable incidents worldwide. We would like to show you a description here but the site won’t allow us. (d) How will you calculate the volume of n drops of this solution of oleic acid? If momentum (P ), area (A) and time ( T ) are taken to be fundamental quantities, then energy has the dimensional formula. Option to view a computer animation at the particle level of the interaction of the M2+ ion with the metal electrode. Eckhoff, Rolf K. (1997). Escaping powder When a hot wire is plunged into a beaker of water with powder (e.g. We would like to show you a description here but the site won’t allow us. Knowing the volume of the drop and area of the film we can calculate the thickness of the film which will give us the size of oleic acid molecule. Secondary dust explosions are the result of dust accumulation inside a building being disturbed and ignited by the primary explosion, resulting in a much more dangerous uncontrolled explosion that can affect the entire structure. Great Britain: January 1983. 13.12 Nuclear Fusion 476 13.13 Controlled Fusion 477 13.14 Particle Accelerators 481 Summary 487 Solved Examples 492 Objective Type Questions 508 Short-Answer Questions 512 Practice Problems 513 Unsolved Questions 515 14. Which of the following are not a unit of time? Not if you're careful. Even materials that are traditionally thought of as nonflammable (such as aluminum), or slow burning (such as wood), can produce a powerful explosion when finely divided, and can be ignited by even a small spark. There are many sources of ignition, and a naked flame need not be the only one: over one half of the dust explosions in Germany in 2005 were from non-flame sources. [CHEX %PARSER=2.13 %FLOATED=19991204 %GENERATED=DR/ALL %BOUND=TRUE] A dictionary file. A physical quantity X is related to four measurable quantities a, b, c and d as follows: If velocity of light c, Planck’s constant h and gravitational contant G are taken as fundamental quantities then express mass, length and time in terms of dimensions of these quantities. Workers who need illumination in enclosed spaces where a dust explosion is a high risk often use lamps designed for underwater divers, as they have no risk of producing an open spark due to their sealed waterproof design. If Planck’s constant (h ) and speed of light in vacuum (c ) are taken as two fundamental quantities, which one of the following can, in addition, be taken to express length, mass and time in terms of the three chosen fundamental quantities? On the basis of dimensions, decide which of the following relations for the displacement of a particle undergoing simple harmonic motion is not correct: If P, Q, R are physical quantities, having different dimensions, which of the following combinations can never be a meaningful quantity? Static charges can be generated by external sources, or can be internally generated by friction at the surfaces of particles themselves as they collide or move past one another. Now, lycopodium powder is sprinkled evenly over the film and its diameter is measured. Explosive dust can arise from activities such as transporting grain, and grain silos have often been demolished violently. 8. Lycopodium powder is a yellow-tan dust-like powder historically used as a flash powder. Powdered gloves are usually lubricated with cornstarch because other powdering options (lycopodium powder, talc, etc.) Dust is defined as powders with particles less than about 500 micrometres in diameter, but finer dust will present a much greater hazard than coarse particles by virtue of the larger total surface area of all the particles. The same method is also used in large storage tanks where flammable vapors can accumulate. Although not strictly a dust, paper particles emitted during processing - especially rolling, unrolling, calendaring/slitting, and sheet-cutting - are also known to pose an explosion hazard. Units and Measurement Class 11 Notes Physics Chapter 2 Measurement The process of measurement is basically a comparison process. The series of coal dust explosions within a mine rocked the close-knit township and was audible as far as 30 kilometres (19 mi) away. The dust is dispersed in the air at a sufficiently high, The area is confined—a building can be an enclosure, Demonstration of an open-air dust explosion, Deflagration venting through a dust retention and flame-arresting device, This page was last edited on 16 January 2021, at 13:33. Measure of two quantities along with the precision of respective measuring instrument is A = 2.5 m s, You measure two quantities as A = 1.0 m ± 0.2 m, B = 2.0 m ± 0.2 m. We should report correct value for √. A dust explosion is the rapid combustion of fine particles suspended in the air within an enclosed location. Also, particulate suspensions of compounds with a high oxidative potential, such as peroxides, chlorates, nitrates, perchlorates, and dichromates, can increase risk of an explosion if combustible materials are also present. (c) What would be the volume of oleic acid in each mL of solution prepared? Why do we have different units for the same physical quantity? The sudden release of energy from a "detonation" can produce a shockwave, either in open air or in a confined space. Determination of thermal conductivity of a bad conductor by Lee’s disc method. Now, lycopodium powder is sprinkled evenly over the film and its diameter is measured. Scabies is a skin infection caused by the mite sarcoptes scabiei. [4] A similar problem occurs in sawmills and other places dedicated to woodworking. When this mixture of fuel and air is ignited, especially in a confined space such as a warehouse or silo, a significant increase in pressure is created, often more than sufficient to demolish the structure. Determination of particle size of lycopodium powder using semiconductor laser. lycopodium) floating on the surface, the powder moves rapidly. 34% of the miners working that day were killed. I got interested in this as a programming topic reading the Programmer’s Challenge in MacTech magazine. Here we have provided NCERT Exemplar Problems Solutions along with NCERT Exemplar Problems Class 11. abs acos acosh addcslashes addslashes aggregate aggregate_info aggregate_methods aggregate_methods_by_list aggregate_methods_by_regexp aggregate_properties aggregate_properties_by This means that each mL of solution contains 1/20 mL of oleic acid. c) 20mL of oleic acid contains 1mL of oleic acid. Dust explosions are a frequent hazard in coal mines, grain elevators, and other industrial environments. sound waves (b) The displacement is maximum at the antinode of the sound waves. [7] A combustible concentration at or below 25% of the LEL is considered safe. CBSE Important Questions for Class 11 Physics, NCERT Important Questions for Class 11 Physics, NCERT Solutions for Class 8 Sanskrit Chapter 11 सावित्री बाई फुले, NCERT Solutions for Class 12th Macroeconomics : Chapter 6 – Open Economy Macroeconomics, Class 11 Important Questions for Physics - Motion in a Straight Line, The number of significant figures in 0.06900 is, The sum of the numbers 436.32, 227.2 and 0.301 in appropriate significant figures is, The mass and volume of a body are 4.237 g and 2.5 cm, The numbers 2.745 and 2.735 on rounding off to 3 significant figures will give, The length and breadth of a rectangular sheet are 16.2 cm and 10.1cm, respectively. Glockenspiel problem: From redistribution of lycopodium powder I have verified that there are 2 nodal lines which for a 790Hz G are about 14 cm apart. Where the dust is carbon based (such as in a coal mine), incomplete combustion may cause large amounts of carbon monoxide (the miners' after-damp) to be created. To support rapid combustion, the dust must consist of very small particles with a high surface area to volume ratio, thereby making the collective or combined surface area of all the particles very large in comparison to a dust of larger particles. The alternatives for making processes and plants safer depend on the industry. In addition, many otherwise mundane organic materials can also be dispersed into a dangerous dust cloud, such as grain, flour, starch, sugar, powdered milk, cocoa, coffee, and pollen. Question from very important topics are covered by NCERT Exemplar Class 11. Since burning can only occur at the surface of a solid or liquid, where it can react with oxygen, this causes dusts to be much more flammable than bulk materials. Destroyed the largest grain mill in the world and leveled five other mills, effectively reducing the milling capacity of Minneapolis by one-third to one-half. Parts built from metallic powder require extra precautions", "Dust explosion concentration — Physical meaning and use in risk assessment of powder minimum explosive concentration (MEC)", "47 Die, 179 Injured in Blast at Linen Mill in Northeast China", "Bosley explosion: Four missing in Wood Flour Mills blast", "Bosley Wood flour mill explosion: Fourth body found in wreckage of building gutted by blast", Combustible dust explosion investigation products, Hazard Monitoring Equipment - Selection, Installation and Maintenance, http://www.hse.gov.uk/pubns/books/hsg103.htm, https://en.wikipedia.org/w/index.php?title=Dust_explosion&oldid=1000738845, Articles with French-language sources (fr), Srpskohrvatski / српскохрватски, Creative Commons Attribution-ShareAlike License. For example, the LEL for sawdust has been determined to be between 40 and 50 grams/m3. In an experiment to estimate the size of a molecule of oleic acid 1 mL of oleic acid is dissolved in 19 mL of alcohol. Physics Important Questions Class 11 are given below. In special effects pyrotechnics, lycopodium powder[2] and non-dairy creamer[6] are two common means of producing safe, controlled fire effects. Since the advent of industrial production–scale metal powder–based additive manufacturing (AM) in the 2010s, there is growing need for more information and experience with preventing dust explosions and fires from the traces of excess metal powder sometimes left over after laser sintering or other fusion methods. make 1 parsec? (b) Angular momentum and Planck’s constant. To measure a physical quantity, we have to find out how many times a standard amount of that physical quantity is present in the quantity being measured. Photon is quantum of radiation with energy E = hν where ν is frequency and h is Planck’s constant. Why length, mass and time are chosen as base quantities in mechanics? How many magnitudes higher is the volume of atom as compared to the volume of nucleus? Historically, fatalities from dust explosions have largely been the result of secondary dust explosions. Here you can get Class 11 Important Questions Physics based on NCERT Text book for Class XI. The displacement of a progressive wave is represented by y = A sin(wt – k x ), where x is distance and t is time. have been found to irritate tissue. When a source cannot be found, ignition will often be attributed to static electricity. It takes an English sentence and breaks it into words to determine if it is a phrase or a clause. However, even cornstarch can impede tissue healing, so powder-free gloves are often preferred for surgeries and other sensitive procedures. The radius of atom is of the order of 1 Å and radius of nucleus is of the order of fermi. Which of the following measurements is most precise? IN order to render the Dictionary more portable and convenient in size, the Author has thought it best to abridge the larger work and bring it out in its present form. During a total solar eclipse the moon almost entirely covers the sphere of the sun. Protecting process plant and grain handling facilities from the risk of dust hazard explosions: rapid combustion of fine particles suspended in the air.
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