Physics-DPP-1-8.Fluid Mechanics

PHYSICS Topic: FLUID MECHANICS Date: 1. A raft of wood of mass 120 kg floats in water. The weight that can be put on the raft to make it just sink, should be : (d = 600 kg /m3) (a) 80 kg (b) 50 kg (c) 60 kg (d) 30 kg 2. A balloon has volume of 1000 m3. It is filled with hydrogen (ρ = 0.09 g/L). If the density of air is 1.29 g/L, it can lift a total weight of (a) 600 kg (b) 1200 kg (c) 300 kg (d) 1800 kg 3. A tank full of water has a small hole at its bottom. Let t1 be the time taken to empty the first half of the tank and t2 be the time needed to empty the rest half of the tank, then : (a) t1 = t2 (b) t1 > t2 (c) t1 < t2 (d) t1 = 0.523 t2 4. A ball of relative density 0.8 falls into water from a height of 2 m. The depth to which the ball will sink is (neglect viscous forces): (a) 8 m (b) 2m (c) 6 m (d) 16 m 5. A cylindrical vessel of 92 cm height is kept filled up to the brim. It has four holes 1,2, 3, 4 which are respectively at heights of 20 cm, 30 cm, 46 cm and 80 cm from the horizontal floor. The water falling at the maximum horizontal distance from the vessel comes from : (a) hole number 4 (b) hole number 3 (c) hole number 2 (d) hole number 1 6. A block of wood is floating on the surface of water in a beaker. The beaker is covered with a bell jar and the air is evacuated. What will happen to the block ? (a) Sink a little (b) Rise a little (c) Remain unchanged (d) Sink completely 7. Two substances of relative densisites ρ and ρ2 are mixed in equal volume and the relative density of mixture is 4. When they are mixed in equal masses, the relative density of the mixture is 3. The values of ρ1 and ρ2 are : (a) ρ1 = 6 and ρ2 = 2 (b) ρ1 = 3 and ρ2 = 5 (c) ρ1 = 12 and ρ2 = 4 (d) none of these 8. A closed rectangular tank is completely filled with water and is accelerated horizontally with an acceleration towards right. Pressure is (i) maximum at, and (ii) minimum at : (a) (i) B (ii) D (b) (i) C (ii) D (c) (i) B (ii) C (d) (i) B (ii) A 9. In the given figure, the velocity v3 will be : (i) 2 m/s (b) 4 m/s (c) 1 m/s (d) 3 m/s PHYSICS Topic: FLUID MECHANICS Date: 10. A uniformy tapering vessel is filled with a liquid of density 900 kg m–3. The force that acts on the base of the vessel due to the liquid (excluding atmospheric force ) is : (g = 10 m/s2) (i) 3. 6 N (b) 7. 2 N (c) 9. 0 N (d) 12.6 N PHYSICS Topic: FLUID MECHANICS Date: 1. (a) 2. (b) Answer Key 3. (c) 4. (a) 5. (b) 6. (c) 7. (a) 8. (a) 9. (c) 10. (b)

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