Page 1 : Multiple choice type :, (b) its tube is slightly tilted from vertical ?, (c) a drop of liquid is inserted inside the tube ?, Ans. (a) remains unaffected (b) remains unaffected, %3D, (c) 1 torr = 1 mm of Hg (d) 1 torr = 1 m, of Hg, %3D, (c) decreases, Ans. (c) 1 torr = 1 mm, 19. State two uses of a barometer., 2. The normal atmospheric pressure is :, 20. Give two reasons for the use of mercury as a barometric, liquid., (b) 76 cm of Hg, (a) 76 m of Hg, (c) 76 Pa, (d) 76 N m-2, 21. Give two reasons why water is not a suitable barometric, liquid., Ans. (b) 76 cm of He, 3. The atmospheric pressure at earth surface is, oub and inside a mine is P,. They are related as :, a(a) P, = P2, (c) P¡ < P2, 22. Mention two demerits of a simple barometer and state, how they are removed in a Fortin barometer., 23. Draw a simple labelled diagram of a Fortin barometer, and state how it is used to measure the atmospheric, (b) P¡ > P2, (d) P2=0, Ans. (c) P,<P,, pressure., Numericals :, 24. What is an aneroid barometer ? Draw a neat and, labelled diagram to explain its construction and, working., 1. Convert 1 mm of Hg into pascal. Take density di, Hg = 13-6 x 10³ kg m-3 and g = 9-8 m s2., Ans. 133-28 P, 25. State two advantages of an aneroid barometer over a, simple barometer., 2. At a given place, a mercury barometer records a, pressure of 0-70 m of Hg. What would be the, height of water column if mercury in barometar, is replaced by water ? Take density of, 13-6 x 103 kg m-3., 3. At sea level, the atmospheric pressure is 76 cm oi ne, air pressure falls by 10 mm of Hg per 120 m of asce, 26. How is the reading of a barometer affected when it is, taken to (i) a mine, and (ii) a hill ?, mercury, Ans. 9-52 m, Ans. (i) increases (ii) decreases., 27. How does atmospheric pressure change with altitude?, Draw an approximate graph to show this variation., 28. State two factors which affect the atmospheric pressure, as we go up., d 70 cm Hg. State the assumption made by you., 29. Why does a fountain pen leak at a high altitude ?, Ans. 720 m, 30. Why does our nose start bleeding on high mountains ?, 31. What is an altimeter ? State its principle. How is its, ascent., scale calibrated ?, 32. What do the following indicate in a barometer regarding, Assuming g =, weather :, atmosphere., W 0008 su, (a) gradual fall in the mercury level,, (b) sudden fall in the mercury level,, the fall in barometric height in mm of He, height, at a, (c) gradual rise in the mercury level, = 13-6 x 103 kg m-3., Ans. 10 mm, 射J0U, 10 m s-2 and density of air to be uniform, 5. Assuming the density of air to be 1-295 kg m? find, Assumption : Atmospheric pressure falls linearly with, and equal to 13 kg m-3, find the height of the, 4. At sea level, the atmospheric pressure is 1-04 x 10 Pa, what is the height of a hill where the barometer reads, of 107 m above the sea level. Take density of mercury, (a) 1 torr = 1 cm of Hg (b) 1 torr = 0-76 m of Hg, 1. The unit torr is related to the barometric height as: