More About Solids, Liquids and Gases ASSIGNMENT

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1 More About Solids, Liquids and Gases ASSIGNMENT 1. Fill in the blank spaces by choosing the correct words from the list given below: List : water, density, altitudes, lateral, intermolecular, force, cohesion, upward, atmosphere, decreases. (a) Solid do not flow like liquid, because of very strong... force. (b) The kinetic energy of the molecules of matter... with the fall in temperature. (c) The air pressure can support m of... at sea level. (d) The buoyant force decreases with the decrease in... of a liquid. (e) The thick wall near the base of a dam counters large... pressure of water. (f) The atmospheric pressure decreases on higher.... (g) 76 cm vertical height of mercury exerts as much pressure, as is exerted by... (h) Surface tension in the liquids, is caused due to the force of.... (i) The foot valve of lift pump opens in the... direction. 2. Statements given below are incorrect. Write the correct statements. (a) The intermolecular forces in case of liquids are less than gases. (b) When a body is floating in a liquid, then the weight of whole body is equal to the volume of liquid displaced by the body. (c) The piston valve of a lift pump opens in both directions. (d) The pressure of enclosed mass of a gas increases with the increase in volume. (e) When a body sinks in a liquid then the weight of whole body is less than the weight of liquid displaced by the body. (f) On higher altitudes the atmospheric pressure is more than 76 cm of mercury. (g) It is the force of gravitation which turns small mass of mercury in silvery spheres. (h) Stones are carried to long distance by fast flowing river, because the stones weigh less in air and more in water. 1 \\Dharambir\D:\2009\Assignment\LE Physics-8(ICSE)\Ch-04

2 (i) The atmospheric pressure at sea level is 1,00,000 newtons. (j) The lift pump will lift underground water only, if the depth of underground water is more than m. 3. Write True or False in front of the statements given below : (a) Conduction takes place due to molecular movement. (b) The atmospheric pressure is about 100,000 Pa. (c) The phenomenon, due to which surface of a liquid behaves like a stretched membrane, is called surface tension. (d) With the decrease in intermolecular space, the intermolecular forces decrease. (e) Aneroid barometer uses pure mercury. (f) More the density of a liquid, more is the pressure it exerts. (g) Iron floats on the surface of mercury, because its density is more than that of mercury. (h) Solids get heated only by conduction. (i) With the decrease in the volume of gas, its pressure increases. (j) In an enclosed space, the pressure is transmitted equally in all directions. 4. Tick ( ) the most appropriate answer. (a) The fluid used in aneroid barometer is : (i) water (ii) mercury (iii) air (iv) alcohol (b) The normal atmospheric pressure is : (i) 70 cm of mercury (ii) 76 cm of mercury (iii) 67 cm of mercury (iv) 80 cm of mercury (c) The intermolecular spaces in case of liquids are : (i) less than solids (ii) more than gases (iii) more than solids (iv) more than solids and gases (d) The kinetic energy of molecules of a gas increases with : (i) fall in temperature (ii) rise in temperature (iii) decrease in pressure (iv) increase in pressure (e) The pressure exerted at any point on an enclosed liquid, is transmitted : (i) only towards the sides of the vessel (ii) only towards the base of the vessel (iii) in all directions of the vessel 2

3 (iv) none of these (f) When a body is fully immersed in liquid, the apparent loss in the weight of the body is equal to : (i) volume of liquid displaced by the body (ii) density of the liquid (iii) weight of liquid displaced by the body (iv) none of these (g) An ink fountain pen leaks on high altitude, because : (i) pressure of atmosphere is more than pressure inside the pen (ii) pressure of atmosphere is less than pressure inside the pen (iii) the density of ink on high altitude decreases (iv) none of these (h) When the weight of a given body is less than the weight of fluid displaced by it, then the body : (i) sinks (ii) floats (iii) just keeps in line with the surface of fluid (iv) none of these (i) Buoyant force exerted by a fluid on a given body, is : (i) equal to the volume of body (ii) equal to the weight of body (iii) equal to the volume of the fluid displaced by the body (iv) equal to the weight of the fluid displaced by the body. (j) Heat is transmitted in the liquids by : (i) conduction (ii) convection (iii) both conduction and convection (iv) none of these 5. Find the odd one out. Give a reason for your choice. (a) floatation, intermolecular spaces, intermolecular forces, kinetic energy. (b) a sailing ship, a hydrogen filled balloon, a large stone, swimming duck. (c) buoyant force, weight, mass, apparent weight. (d) a lift pump, a barometer, suction pad, sailing boat. 6. On the basis of kinetic model explain, why the solids have a definite shape and definite volume? 3 \\Dharambir\D:\2009\Assignment\LE Physics-8(ICSE)\Ch-04

4 7. On the basis of kinetic model explain, why the liquids have a definite volume, but no definite shape? 8. On the basis of kinetic model explain, why the gases have neither definite shape nor definite volume? 9. (a) What do you understand by the term surface tension in liquids? (b) Amongst the force of cohesion and force of adhesion, which force is responsible for the surface tension in liquids? (c) When a drop of mercury is allowed to fall on a clean glass plate, it splits to form tiny droplets of mercury, which are spherical in shape. Explain. 10. (a) What do you understand by the term meniscus? (b) About 10 cc of mercury and 10 cc of water is poured into two separate tubes. Name the kind of meniscus formed by : (i) Mercury (ii) Water 11. On the basis of kinetic model of matter explain, why do liquids exert pressure on the sides of containing vessel. 12. On the basis of kinetic model of matter explain, why do gases exert same pressure in all directions on the sides of containing vessel. 13. On the basis of kinetic model explain, why the pressure of the enclosed gas increases with the decrease in the volume of gas. 14. On the basis of kinetic model explain : (a) Heat conduction in solids (b) Heat convection in liquids 15. Fill in the blank spaces with correct words related to kinetic model of matter. (a) Molecules in any state of matter are in... motion, which does not stop over any length of.... (b) Due to the continuous motion of the molecules of matter, they possess... energy. (c) The kinetic energy of the molecules of matter... with the increase in temperature. 4

5 (d) The molecules of matter always... each other. (e) The force of attraction between similar kind of molecules, is called force of.... (f) The force of attraction between different kind of molecules, is called force of.... (g) The empty spaces between the molecules of matter, is called... space. (h) The force of attraction between the molecules of matter... with the increase in intermolecular spaces. 16. State any three factors which determine pressure in liquids. 17. Explain the following : (a) Why is the wall of a dam made very thick near the base? (b) Why do the deep sea divers wear specially designed suits? 18. (a) What do you understand by the term atmospheric pressure? (b) What is the magnitude of atmospheric pressure at sea level in SI unit? (c) How does atmospheric pressure change with the increase in altitude and why? (d) In terms of vertical column of mercury, how much is atmospheric pressure at sea level? (e) How is barometric height affected, if the mercury used in barometer is damp? (f) How is barometric height affected, if the barometer tube is not of uniform bore? 19. (a) What for is lift pump used? (b) State the principle on which lift pump is based. 20. Why do the astronauts wear specially designed space suits? 21. Why is one s hearing affected while climbing up a steep hill? 22. Why is it not possible to suck lemonade with the help of a straw on the surface of moon? 23. Why does a fountain pen starts leaking on high altitudes? 5 \\Dharambir\D:\2009\Assignment\LE Physics-8(ICSE)\Ch-04

6 24. Why do the bodies of deep sea fish burst when brought on the surface of the sea? 25. (a) What do you understand by the following terms? (i) Buoyancy (ii) Buoyant force (b) State two factors which determine the buoyant force acting on a body. (c) A stone suspended from a spring balance, is first weighed in water and then in salt solution of density 1.2 g cm 3. In which case the spring balance will register less weight and why? 26. (a) State Archimedes principle. (b) A stone of volume 20 cc, weighs 70 g in air. When the stone is fully immersed in water and weighed by spring balance, its weight is 50 g. At the same time 20 cc of water is displaced. (i) How much is the apparent loss of weight of stone in water? (ii) How much is the weight of water displaced by the stone? (iii) Which physical law is explained by the answers in (i) and (ii)? 27. (a) If a cork is forced into water by applying some force, such that W is the weight of cork and R is the buoyant force, which is greater amongst W and R? (b) If the force applied on cork is removed, what will you observe? (c) Will the buoyant force acting on the cork in (b) will be less than or more than R? (d) How is the new value of buoyant force, compared with weight of a cork? 28. Why does the ice float on the surface of water? 6

PHYS:1200 LECTURE 13 FLUIDS (2)

1 PHYS:1200 LECTURE 13 FLUIDS (2) Lecture 13 deals with the properties of fluids at rest or fluid statics. We will be discussing mostly liquids and will introduce two important principles of fluid statics: