FLOATATION 9

Practice Paper

Physics (2019)

   Class IX                         CH - 10  FLOATATION                                     

1. State Archimedes Principle?
2. What makes a body to float or sink in a liquid? 
3. Define density and relative density? Calculate the pressure at a depth of 50 m below the surface of the sea. The density of seawater is 1024 Kg/m3.
4. What are the fluids? What are the factors on which the upward pressure at a point on a fluid depends?
5. Define Pressure? How is thrust different from Pressure? 
6. Write the units of pressure and Relative density.
7. What is the S.I unit of pressure?
8. Give a mathematical proof of the Archimedes principle? 
9. What is the upthrust experienced by a balloon of volume 120 m3 filled with hydrogen? The density of air = 1.140 Kg/m3 and density of hydrogen =0.081 Kg/m3 at room temperature. What is the maximum weight this balloon can lift?
10. What is the upthrust experienced by a cube of edge – length 5cm made of iron when completely immersed in ethanol of density 0.8 g/cm3.
11. A cylindrical block of wood of height 4.2 m and mass 100 Kg floats vertically in the water. The relative density of wood is 0.8.
    (a) What height of the block will be seen above the water?
    (b) If the block of the lead of mass 10kg is placed, what height of the block will be seen above water?
12. Give one reason why a block of plastic when released underwater comes up to the surface of the water. 
13. When we jump into a swimming pool we feel lighter. Why?
14. What is meant by upthrust?
15. State two factors on which the upthrust force depends?
16. What are the two forces act on the object in the vertically opposite direction when the object is immersed into the liquid?
17. Define the relative density of a substance?
18. What are the fluids?
19. In what direction does the buoyant force act on an object immersed in a liquid?
20. Why does object float or sink when placed on the surface of the liquid?
21. An iron nail floats on mercury but sinks in water. Why?  
22. A woman walking in high hills can damage a hardwood floor by making small dimples on the floor since her weight is concentrated on such a small area. If the women weigh 60N and tip of the high heel is 2 cm², what will be the pressure exerted on the floor by her high heel? 
23. A cube of side 5 cm is immersed in water and then in the saturated salt solution. In which case will it experience a greater buoyant force? If each side of the cube is reduced to 4 cm and then immersed in water compare force experienced by the cube, as compared to the first case. Give reasons for each case. 
24. The volume of 50 gm of a substance is 20cm³. If the density of the water is 1 g cm^-3, will the substance float or sink in water? Justify your answer.
25. The pressure exerted by the weight of a cubical block of side 4 cm on the surface is 10 Pascal. Calculate the weight of the block.
26. Give reasons:(i) Why do buildings have a wide foundation? (i)Tractors have broad tires.
27. Out of the positions given below, in which case do you apply more pressure on loose sand and why?
    (i) While you are standing
    (ii) while you lie down. Why does an army tank rest upon a continuous chain?
28. A metallic block of 6 kg is dropped into a water tank. The volume of the block is given to be 3 x 10^-3m³ and density of water is 10³ kg/m³. Find (a) Buoyant force on the block, (b) density of the metallic block.
29. Why is a bucket of water lighter when in water than when it is taken out of water?
30. A ball of mass 4 kg and density 4000 kg m³ is completely immersed in water of density 10³ kg m^-3. Find the buoyant force on the ball.(Given g = 10 ms^-2).
31. (i) An object of volume V is immersed in a liquid of density p. Calculate the magnitude of a buoyant force acting on the object due to the liquid?
    (ii) Mention the direction of buoyant force.
32. Why is it difficult to hold a bag having a strap made of a thin and strong string?
33. What happens when :
    (i) The buoyant force exerted by the fluid is greater than the weight of the body
    (ii) Buoyant exerted by the fluid is equal to the weight of the body?
34. State Archimedes’ Principle. Give two applications of this principle.
35. A sphere of iron and another of wood having the same radius are held underwater. Which of these experiences a greater buoyant force?
36. (i)The density of water is 10³ kg/m³ If the relative density of Al is 2.7, calculate the density of Al in g/cm³.
    (ii) If the relative density of Ag is 10.8, calculate the density of At in g/cm³.
37. The dimension of the wooden block is 2 m x 25 m x 0.10 m. If the relative density of wood is 0.6, calculate the mass of the block in kg. Density of the water = 10³ kg/m³.
38. (i) Why are railway tracks laid on large-sized concrete sleepers?
    (ii) While drawing water from a well, the bucket of water appears to be heavier as it comes out of the water.
39. (i) Name the instrument which is used to determine the density of a liquid.
    (ii) The volume of a 250 gm sealed packed is 500 cm³. Will the packet float or sink in water, if the density of water is 1 g/cm³.
40. The volume of a 500 gm sealed packed is 350 cm³. Its density is 1.4 g/cm³. What will be the mass of the water displaced by this packet? (Density of water = 1 g/cm³).
41. What would be the apparent weight of an iron block of size 5 cm x 5 cm x 5 cm when it is completely immersed in water? (Density of iron = 7.8 g/c.c).
42. Define pressure and state its S.I unit. The dimensions of a metallic cuboid are 30 cm x 20 cm x 15 cm and its mass is 30 kg. If the acceleration due to gravity is 10 m/s².Calculate the pressure exerted by the cuboid when it is resting on the face having sides 20 cm x 15 cm on a table. 
43. Define thrust and state its S.I unit.
44. An iron cube of side 10 cm is kept on a horizon table. If the density of iron is 8000 kg/m³. Find the pressure on the portion of the table where the cube is kept. (g = 10 m/s². ) 
45. A cubical block of side 2 cm is lying on a table. If the density of the material of the cube is 10.000 kg/m3, find the pressure exerted by the block on the table. (g = 10 m/s². ) 
46. Lactometers are used to determine the purity of a sample of milk. State the principle on which this instrument is based on.
47. (i) Define density. 
    (ii) State unit of density in S.I. 
    (iii) How can we identify whether the substance is pure or not by knowing its density?
48. How the Archimedes principle is used to design ships and submarines.
49. Mention the uses of Lactometer and Hydrometer.
50. Deduce the formula for the buoyant force acting on a fully immersed object in terms of its volume, the density of liquid and acceleration due to gravity.
51. The weight of the balloon and gas inside it is 12N. The volume of the balloon is 1200 m^3. The density of air is 1.26 Kg/m^3. 
    Calculate (a) the weight it can lift(b) the acceleration as it rises.