66 Fluid Mechanics 3. Calculate the pressure due to a column of 0.4 m of (a) water, (b) an oil of sp. gr. 0.9, and (c) mercury of sp. gr. (Ans. (a) 0.3924 N/cm², (b) 0.353 N/cm², (c) 5.33 N/em²} 4. The pressure intensity at a point in a fluid is given 4.9 N/cm². Find the corresponding height of fluid when it 13.6. Take density of water, p = 1000-~g. [Ans. (a) 5 m of water, (b) 6.25 m of oil is: (a) water, and (b) an oil of sp. gr. 0.8. 5. An oil of sp. gr. 0.8 is contained in a vessel. At a point the height of oil is 20 m. Find the corresponding (Ans. 16 m) height of water at that point. 6. An open tank contains water upto a depth of 1.5 m and above it an oil of sp. gr. 0.8 for a depth of 2 m. Fd the pressure intensity : (i) at the interfüce of the two liquids, and (ii) at the bottom of the tank. [Ans. () 1.57 N/cm², (il) 3.04 N/em²| 7. The diameters of a small piston and a large piston of a hydraulic jack are 2 cm and 10 cm respectively, A force of 60 N is applied on the small piston. Find the load lifted by the large piston, when : (a) the pistons aae at the same level, and (b) small piston is 20 cm above the large piston. The density of the liquid in the jack s [Ans. (a) 1500 N, (b) 1520.5 NJ kg given as 1000- m 8. Determine the gauge and absolute pressure at a point which is 2.0 m below the free surface of water. Take [Ans. 1.962 N/cm² (gauge), 12.066 N/cm² (abs.)] 9. A simple manometer is used to measure the pressure of oil (sp. gr. = 0.8) flowing in a pipe line. Its right limb is open to the atmosphere and left limb is connected to the pipe. The centre of the pipe is 9 cm below the level of mercury (sp. gr. 13.6) in the right limb. If the difference of mercury level in the two limbs is 15 (Ans. 12.058 Nlem'] 10. A simple manometer (U-tube) containing mercury is connected to a pipe in which an oil of sp. gr. 0.8 is flowing. The pressure in the pipe is vačuum. The other end of the manometer is open to the atmosphere. Find the vacuum, pressure in pipe, if the difference of mercury level in the two limbs is 20 cm and height [Ans. - 27.86 N/em³] 11. A single column vertical manometer (le., micrometer) is connected to a pipe containing oil of sp. gr. 0.9. The area of the reservoir is 80 times the area of the manometer tube. The reservoir contains mercury of sp. gr. 13.6. The level of mercury in the reservoir is at a height of 30 cm below the centre of the pipe and difference of mercury levels in the reservoir and right limb is 50 cm. Find the pressure in the pipe. (Ans. 6.474 N/cm*] 12. A pipe contains an oil of sp. gr. 0.8. A differential manometer connected at the two points A and B of the pipe shows a difference in mercury level as 20 cm. Find the difference of pressure at the two points [Ans. 25113.6 N/m) atmospheric pressure as 10.1043 Ncm². cm, determine the absolute pressure of the oil in the pipe in N/cm². of oil in the left limb from the centre of the pipe is 15 cm below.