1. An ideal fluid flows through a pipe of circular cross-section made of two sections with diameters 2.5 cm and 3.75 cm. The ratio of the velocities in the two pipes is

2. Why the aeroplanes are made to run on the runway before take off?

3. One end of a towel dips into a bucket full of water and other end hangs over the bucket. It is found that after some time the towel becomes fully wet. It happens

4. An ice cube contains a large air bubble. The cube is floating on the surface of water contained in a trough. What will happen to the water level, when the cube melts?

5. If the surface of a liquid is plane, then the angle of contact of the liquid with the walls of container is

6. The surface of water in contact with glass wall is

7. When the temperature of a liquid increases, its surface tension

8. The addition of soap changes the surface tension of water to T₁ and that of sugar changes it to T₂. Thus

9. Two soap bubbles have radii in the ratio of 4 : 3. What is the ratio of work done to below these bubbles?

10. When the angle of contact between a solid and a liquid is 90°, then

11. Water rises up to a height of 4 cm, in a capillary tube immersed vertically in water. What will be the length of water column in the capillary tube, if the tube is immersed in water, at an angle of 60° with the vertical?

12. 5 g of water rises in the bore of capillary tube when it is dipped in water. If the radius of bore capillary tube is doubled, the mass of water that rises in the capillary tube above the outside water level is

13. Water rises up to a height h, in a capillary tube of radius r. the mass of the water lifted in the capillary tube is M. if the radius of the capillary tube is doubled, the mass of water that will rise in the capillary tube will be

14. A capillary tube when immersed vertically in a liquid records a rise of 3 cm. if the tube is immersed in the liquid at an angle of 60° with the vertical, then length of the liquid column along the tube will be

15. The height of a liquid in a fine capillary tube

16. Along a streamline

17. For a floating body to be in stable equilibrium, where should its centre of buoyancy be located?

18. If two pieces of metal when immersed in a liquid have equal upthrust on them, then both pieces have equal

19. A person is carrying a bucket in one hand and a fish in the other. If he puts fish in the’bucket, how will the load carried by the person change?

20. The angle of contact at the interface of water-glass is 0o, ethyl alcohol-glass is 0o, mercury-glass is 140o, and methyl iodide-glass is 30o. A glass capillary is put in a trough containing one of these four liquids. It is observed that the meniscus is convex. The liquid in the trough is