Tag Archives: Measurements

How is maximum occupancy of a building is calculated?

The calculation of maximum occupancy of a building has a significant place in the hazard management. The idea is increasingly influencing new construction methods.

The maximum occupancy of a building is calculated primarily based on two factors. One is the number of available exits in the building and the other is the use of space. The International Building Code has laid down some rules regarding the maximum occupancy of an area. IBC is a model building code developed by the International Code Council (ICC).
As per the definition given by IBC, an exit is a continuous and unobstructed path of vertical or horizontal egress travel from any occupied portion of the building or structure to a public way. Usually, the doors from kitchen and unused rooms are not considered exits.
When calculating the occupancy figure for a building, the two following calculations are used.
1. Floor space factor – The number of persons who can safely reside in the premises. Number of people = Floor area (m²) / Occupant density
2. Exit factor – The width and capacity of the exit routes to allow people to escape safely.
Whichever the less between these figures is the maximum occupancy of a building.
According to the building regulations, the occupant density varies depending on the nature of a building. As per the IBC recommendations, a standing/bar area should have an occupant density of 0.3 M²/person while a shop area could have 2 M²/person and an office area must have 6 M²/person.
Thus, for a bar with an area of 300 M², the maximum occupancy will be 1000. At the same time, an office space with the same area would have a maximum occupancy of 50 as per the floor space factor.
Now we consider the exit factor. As per the recommendations, the ideal width of an escape route or exit is 1050 mm. In any case, it should not be less than 750 mm. An exit with a width of 1050 mm can accommodate 200 Persons in normal conditions. An additional 15 Persons can be accommodated per every 75 mm. If the premises have multiple exits, the wider one is considered to be unavailable. Suppose the above mentioned bar has an exit of 1200 mm width and three exits 1050 mm wide. The total number of persons the exits can accommodate will be 600. Since it is the smaller figure, the maximum occupancy of the premises will be 600.

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What is the formula to calculate IQ? Is IQ of 100 good?

Intelligence is an abstract concept. It is difficult to measure intelligence level and express it in numbers. However, the term Intelligence Quotient is used for the purpose. This term became popular about a hundred years ago in 1916 when a Stanford University psychologist named Lewis Terman invented a formula to numerically measure the amount of intelligence in a human being. The formula was revised in 1937, then in 1960, and the last time in 1972 there were a few changes done to the formula. The formula used today to measure IQ is as follows:

IQ = Mental Age ÷ Physical Age x 100

In the formula, physical age is one’s age from the date of birth, but mental age is a completely different matter. To explain with an example, if a 10-year-old correctly answers questions which can normally only be answered by a 13-year-old, then even though his physical age is 10 years, his mental age is considered to be 13 years. Thus, according to the formula, his IQ would be 13 ÷ 10 x 100 = 130. On the other hand, if a 10-year-old answers questions which can normally only be answered by a 10-year-old (and he can’t answer tougher questions), then his IQ would be 10 ÷ 10 x 100 = 100. It means his mental and physical age are the same.

IQ Distribution

A person with IQ of 100 can not be said to have a sharp mind, because the IQ figure of 100 is normal. It also means that majority of the people the in world have an IQ of 100. Refer above the distribution of Intelligence Quotient.

To tell the truth, human intelligence level can not be determined mathematically with accuracy, intelligence being an abstract concept. Therefore, the formula for measuring IQ is not very reliable. According to this formula a woman named Marilyn vos Savant has IQ of 228, whereas Albert Einstein’s IQ is said to be 160.

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What is horsepower? Why is it calculated on the basis of horse’s physical strength?

In the late 18th century, huge quantities of coal were required to keep up with the increasing demand generated by Industrial Revolution. Proprietors of coal mines in England used strong dray horses for hauling coal out of the underground seams. Some horses, strapped into a harness, were lowered into the shaft to work at the bottom of the pit. One of the serious problems was that few of the mines, especially located far below surface, were flooded with large quantities of water, which had to be pumped out constantly. Dray horses were used for this task also. In fact, horses were the major power source for mines as well as farms.
The Scottish inventor of steam engine, which was to replace horses, had to associate the power output of his engine with that of a horse’s power. Watt did all his calculation on this basis and therefore, horsepower became a standard unit of power. The electrical equivalent of one horsepower is 746 watts in the international or SI system of units and heat equivalent is 2,545 BTU/British Thermal Units. James Watt himself defined one horsepower as 550 foot-pounds of work per second. If an engine lifts a 550-pound object to a height of 2 feet in 1 second, it is working at the rate of 1,100 foot-pounds per second and is delivering 2 horsepower.

Additional reading:
Horsepower (Wikipedia)

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How do scientists calculate the number of calories in a particular food and the number of calories in a particular exercise?

A calorie is the amount of heat needed to raise the temperature of one gram of water by 1⁰ Celsius. To calculate the number of calories in a certain food, scientists burn the food in a device called bomb-calorimeter. The device uses an electric charge to cause the food to combust, measures the amount of heat produced by the food and expresses that heat in terms of calories.
In point of fact, the amount of energy contained in foods is expressed not in calories but in kilocalories and is always written with a capital C. So, when a nutrition expert says that a particular food item provides 200 calories per 100 grams, s/he is actually referring to kilocalorie which equals to 1000 calories. (Also, 1 kilocalorie = 4184 joules).
The body burns food and gives off heat that represents kilocalorie. To measure the number of such calories consumed during exercise, scientists have built very large calorimeters in which people can live. One type measures the heat given off by the person exercising. Another, called indirect calorimeter, measures the oxygen that is consumed. Oxygen is needed for a substance to burn. An average man who is not very active burns 2,800 calories a day. He can increase the number by about 10 percent by playing squash twice a week and by 15 percent by jogging two hours a week.

The table above gives estimates of the number of calories needed by an average man or woman to perform particular activities for one hour. Men use more calories than women do, because men have more weight to carry around.

Additional reading:
Calorimeter (Wikipedia)

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Why the capacity of air conditioners is expressed in tons instead of horsepowers?

Home air conditioning, once a sure sign of plush living, has today become a way of life for practically everybody. The ton rating doesn’t refer to the weight of the equipment, but to its cooling power. A one ton unit will produce the same amount of cooling as one ton of ice melting in 24 hours.
Engineers sometimes describe cooling capacity in BTUs—British Thermal Units—per hour. One ton = 12,000 BTUs, so a one-ton air conditioning unit can remove 238,000 BTU’s of heat in 24 hours. A two-ton unit can remove twice this amount and so on. Deciding on the right size unit for your home is the easiest thing to go wrong. Many things affect the air conditioning load—the size of the house, how much wall faces the afternoon sun, the amount of shade, roof overhang, windows, even house and roof color. Air conditioning companies frequently use an estimating form that takes a number of such factors into account.

Additional reading:
Air conditioner (Wikipedia)

What is anemometer? How does it work?

Anemometer is an apparatus for measuring the speed of wind. The commonest kind of anemometer is a kind of horizontal three-armed windmill, with a hollow hemispherical cup on the end of each arm. (See photo.)

The pressure on the inside of a cup when it is back to wind overcomes the pressure on the rounded front of the cup on the opposite arm, and the cups revolve at rather more than two-fifths the speed of the wind. The mill moves a pointer round a graduated dial. By timing a given number of revolutions, as shown by the pointer, the speed of the wind is easily calculated.

Additional reading:
Anemometer (Wikipedia)

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Why is the cooling power of air-conditioner measured in tons?

Ton is a unit of measurement of weight. But for air-conditioners it’s used in a different sense. Air-conditioner is an appliance for replacing hot, humid air with cool air. In case of air-conditioning, heat is measured in British Thermal Units (BTU). Suppose 1 cubic foot cooking gas is burned in a room, the heat released in the room is about 1,000 BTU. So much heat is sufficient to melt a small brick of ice within a short time. But let us take an example where larger figures are involved. Now assume that the slab of ice weighs full 1 ton. In order to fully melt this slab of ice in 24 hours 2,88,000 BTU is required. A simple division will give the figure of 12,000 BTU per hour. So a particular model of air-conditioner which can absorb and remove the heat prevailing inside the room at the rate of 12,000 BTU per hour is considered to be of 1 ton capacity. At this rate an air-conditioner of 2 tons capacity disposes off twice the amount of heat (24,000 BTU) in one hour.

Thus, the true meaning of the unit ‘ton’ in the context of an air-conditioner is completely different.

More reading:
Air conditioner (Wikipedia)

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At what speed light travels? How do scientists measure the exact speed?

Ole Rømer

Light travels at the speed of 2,99,792 kilometers per second. We know the exact figure because it has been measured in various ways, and all the measurements agree. It was Galileo who made the first attempt to measure it. He had two observers some miles apart on a clear night, and gave each a lantern which could be covered by a screen. One observer was to uncover his lantern, and the other, as soon as he saw the first observer’s light, was to uncover his lantern. The period between the uncovering of both the lanterns seen was to be measured. Galileo found, however, that light traveled so rapidly that the distance between the two observers was too small for its speed to be measured. Danish astronomer Ole Roemer (picture above), working in Paris, made the first real estimate of the speed of light in 1676, and came to the conclusion that it was 3,09,000 kilometers a second, a figure  later proved to be, remarkably enough, approximately correct. He noticed, in observing the eclipses of the moons of Jupiter, that the intervals between the eclipses of one moon were not always the same, being 16 minutes, 26 seconds greater at one time of the year than at another. He decided that this difference could not be due to any real difference in the period of the eclipses, but must be caused by the greater or lesser distance over which the light had to travel from Jupiter to the Earth when the Earth was at different parts of its orbit, and therefore nearer to or farther from Jupiter.

Different methods of measuring the speed of light have been adopted since, and they all give practically the same figure. Two great French scientists, Hippolyte Fizeau and Leon Foucault, about the middle of the 19th century did the pioneer work. They flashed beams of light back and forth between systems of mirrors and lenses. Fizeau interrupted the beam by the teeth of the revolving cog-wheel; Foucault made one of the mirrors revolve. In each case the speed of light was calculated from the speed of the cog-wheel or of the mirror, but the actual method is too complicated to be described.

Albert Michelson

Both these scientists measured the speed of light to be 2,98,000 kilometers per second. The greatest modern measure of the speed of light was Albert Michelson (photo, left). Nearly all his life Michelson worked on his great problem. While still a young officer serving as instructor of physics at the Annapolis Naval Academy, he greatly improved Foucault’s method and obtained much more accurate results in 1878. In 1924 Michelson resumed his work on the speed of light. He flashed light back and forth between various California mountain peaks, over a distance of as much as 140 kilometers. In 1926 he announced the speed of light as 3,00,000 kilometers a second. Modern scientific experiments indicate that the speed of light is about 2,99,792.45 kilometers per second.

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Which is the softest mineral that has been given the lowest rating of 1 on Mohs scale of mineral hardness?

The softest mineral is talc used for making the talcum powder. German mineralogist Friedrich Mohs arranged different minerals in terms of their hardness and compiled a representative scale in 1812 which is given in the accompanying table.

The hardness of a mineral was determined by its capability make scratch on another mineral. Every mineral given in the table is capable of making scratches on the others mentioned above it whereas it can be scratched by those mentioned beneath it. Although Mohs arranged minerals in one to ten sequential scale it is not regular, i.e. it does not show hardness of minerals on the same proportional scale. For example, diamond is only one stage above corundum in Mohs’ scale but actually it is 42 times harder.

If substances other than minerals are to be rated on Mohs’ scale, fingernail’s hardness is 2, knife blade’s hardness is 5 and steel file’s hardness 5.5.

Additional reading:
Friedrich Mohs (Wikipedia)
Mohs scale of mineral hardness (Wikipedia)

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What is the unit of carat which is used for measuring the weight of diamonds?

A species of tree known as carob grows in the coastal areas of Mediterranean Sea (e.g. in Egypt, Libya, Tunisia, France, and Spain). It reaches the height of about 15 meters. It bears about 30 centimeters long ponds containing five to fifteen seeds which are flat and hard like tamarind seeds. These seeds of carob tree are known as carat. (See the picture.) They contain about 50% sugar so in the time of drought when food is scarce poor people in North Africa eat these seeds in order to survive.

Years ago jewellers of Europe used carob seeds as tiny weights for weighing diamonds because of near uniformity in the weight of these seeds. The difference between weights of any two carob seeds is not more then two to five milligrams. (1 milligram = 0.001 gram). One carob seed weighs about 0.2 gram so it requires 5000 carats against one kilogram weight to make the pans of scale to balance. Nowadays carob seeds are not used to weigh diamonds but the jewellers still use the word carat. According to an international agreement made in 1913 diamonds are weighed against a tiny weight of 200 milligrams, i.e. 0.2 gram.

On the other hand the scale indicating purity of gold is also called carat. When no other metal or impurity is mixed in gold it is considered as 24 carat (100%) gold, whereas in 18 carat gold remaining 6 carats equivalent (24- 18=6 i.e. 25%) comprises of other metal or alloy mixed with gold.

Additional reading:
Carat (mass) (Wikipedia)
Carat (purity) (Wikipedia)

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