WHY DO BIRDS NEVER FALL OFF THEIR PERCHES WHEN SLEEPING. DO THEY, INFACT SLEEP?

Birds have nifty tendon arrangement in their legs. The flexor tendon from the muscle in the thigh reaches down the leg, round the ankle and then under the toes. This arrangement means that, at rest, the bird’s body weight causes the bird to bend its knee and pull the tendon tight, so closing the claws. Apparently this mechanism is so effective that dead birds have been found grasping their perches long after they have died

HOW DOES CARBON CHANGE INTO DIAMOND?

Carbon changes into diamond and graphite in the depths of the earth under high pressure and temperature. The process might have taken millions of years. A french scientist, Moissan verified this theory by experiment. He heated carbon and iron together in an electric furnace at 3500 degrees celsius. Carbon dissolved in the molten iron and the mass was cooled suddenly by dipping in water. Then it was put in acid. The iron dissolved and the residue was found to contain a few very small diamonds and some graphite. These results were confirmed by others too. Today diamonds are mass-produced by this method. Artificial diamonds have the same structure, density and hardness as natural diamonds, but are very small. They are also opaque to X-rays. Hence they are used mostly for making hard-edged cutting tools and dies and for cutting and polishing natural diamonds, and not for making ornaments

WHAT DOES 43 AND 53 GRADE CEMENT MEAN?

Grade denotes the minimum strength obtainable in a cement sample. This is determined after making a mold of it, under specified conditions on the 28th day of it molding. The strength is expressed in mega pascals (MPa). The molds in the shape of cubes are made by mixing cement with equal proportions of three grades of sand- coarse, medium and fine. This is cast in cubes of side about 7.07cm so that a surface area of 50 square centimetres is obtained. Cubes cast thus are removed after 24 hours and cured in water for 28 days. Then they are subject to compression tests. The maximum stress in newton/square mm which they can withstand is measured and given as their compressive strength. If this lies between 33 and 43 N/square mm, it is termed as 33 grade cement. Similarly, if it lies between 43 and 53 N/square mm, it is 43 grade cement and if it is more than 53 N/square mm, it is 53 grade cement. To avoid any discrepancies, always only batches of three cubes are subject to compression tests and their average is taken. Generally 53 grade cement is used for making high strength concretes.

WHY DOES THE MOON LOOK SILVERY AT NIGHT?

The overall appearance of the moon is bright ash grey caused by the dark and bright barren rocky land, where there is no atmosphere. When viewed in a naked eye or through a telescope, there are vast basins called seas, which were filled with molten lava millions of years ago. These are the low land plains appearing dark or dusky for the naked eyes. During the final ending phase of volcanism on the Moon, numerous craters had liberated enormous quantity of glowing gases and mineral vapours through their vents, which had blown in all directions over the surface, depositing the mineral condensates in the form of micron-size glassy spherules, tear drops and other powdery forms. The Lunar surface is full of these bright rays like deposits, which scatter reflect the sunlight quite effectively giving it a bright appearance on the surface. The combined effect of rocks and soil along with the craters and minerals like calcium, aluminium and titanium therefore give a silvery appearance to the naked eye

HOW IS QUANTITY OF WATER IN DAMS AND RESERVOIRS MEASURED?

The quantity of water in dams or reservoirs is estimated by a survey method called contour survey, by the engineering surveyors. This ‘quantity survey’ is actually done prior to the reservoir construction. It can also be estimated while water is present. In survey, the levels of the bed of reservoir are taken by leveling instruments and contour are drawn. This is called contour map. A contour is an imaginary line representing equal elevation points. The area enclosed by a contour is flat. This is simply true in case of reservoir. Two successive contour lines at one foot interval provide the area of water at top and bottom for each segment or slice. The volume of each segment is the average area multiplied by the difference of contour height, which is one foot. All volume of segments are added to get the total volume of water. This is how the volume is computed prior to reservoir construction or when dries. When water is present, the bed levels have to be taken under water. To get the bad level, an equipment called Echo sounder is used. To know the point at which bed level is taken an electronic equipment called total station is employed. Earlier a couple of theodolites were used. A boat with Echo sounder is navigated in water on predetermined parallel lines at specific intervals of 10 metre. Knowing the depth and location of each point of bed, levels are calculated and contour map is drawn. The volume is computed from contour map. Some surveyors calculate on simple cross sectional method also in which the water is divided into several sections like potato chips and all average sectional area is multiplied by distance between sections to provide the volume. There is no change in the method of data collection using boat.