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# Properties of Matter: Important Questions

1. Define stress and strain.

2. State HookeŌĆÖs law of elasticity.

3. Define PoissonŌĆÖs ratio.

4. Explain elasticity using intermolecular forces.

5. Which one of these is more elastic, steel or rubber? Why?

6. A spring balance shows wrong readings after using for a long time. Why?

7. What is the effect of temperature on elasticity?

8. Write down the expression for the elastic potential energy of a stretched wire.

9. State PascalŌĆÖs law in fluids.

10. State Archimedes principle.

11. What do you mean by upthrust or buoyancy?

12. State the law of floatation.

13. Define coefficient of viscosity of a liquid.

14. Distinguish between streamlined flow and turbulent flow.

15. What is ReynoldŌĆÖs number? Give its significance.

16. Define terminal velocity.

17. Write down the expression for the StokeŌĆÖs force and explain the symbols involved in it.

18. State BernoulliŌĆÖs theorem.

19. What are the energies possessed by a liquid? Write down their equations.

20. Two streamlines cannot cross each other. Why?

21. Define surface tension of a liquid. Mention its S.I unit and dimension.

22. How is surface tension related to surface energy?

23. Define angle of contact for a given pair of solid and liquid.

24. Distinguish between cohesive and adhesive forces.

25. What are the factors affecting the surface tension of a liquid?

26. What happens to the pressure inside a soap bubble when air is blown into it?

27. What do you mean by capillarity or capillary action?

28. A drop of oil placed on the surface of water spreads out. But a drop of water place on oil contracts to a spherical shape. Why?

29. State the principle and usage of Venturimeter.

1. State HookeŌĆÖs law and verify it with the help of an experiment.

2. Explain the different types of modulus of elasticity.

3. Derive an expression for the elastic energy stored per unit volume of a wire.

4. Derive an equation for the total pressure at a depth ŌĆśhŌĆÖ below the liquid surface.

5. State and prove PascalŌĆÖs law in fluids.

6. State and prove Archimedes principle.

7. Derive the expression for the terminal velocity of a sphere moving in a high viscous fluid using stokes force.

8. Derive PoiseuilleŌĆÖs formula for the volume of a liquid flowing per second through a pipe under streamlined flow.

9. Obtain an expression for the excess of pressure inside a i) liquid drop

ii) liquid bubble iii) air bubble.

10. What is capillarity? Obtain an expression for the surface tension of a liquid by capillary rise method.

11. Obtain an equation of continuity for a flow of fluid on the basis of conservation of mass.

12. State and prove BernoulliŌĆÖs theorem for a flow of incompressible, non-viscous, and streamlined flow of fluid.

13. Describe the construction and working of venturimeter and obtain an equation for the volume of liquid flowing per second through a wider entry of the tube.

## Conceptual questions

### 1. Why coffee runs up into a sugar lump (a small cube of sugar) when one corner of the sugar lump is held in the liquid?Answer:(i) If sugar cube is dropped into liquid the outermost layer has to dissolve first, then next layer, then next until the whole sugar is dissolved.(ii) The coffee runs up into the pores of sugar lump due to capillary action of the liquid.2. Why two holes are made to empty an oil tin?Answer:When oil comes out from a hole of an oil tin, pressure inside it decreased than the atmosphere. Therefore, the surrounding air rush up into the same hole prevents the oil to come out. Hence two holes are made to empty the oil tin.3. We can cut vegetables easily with a sharp knife as compared to a blunt knife. Why?Answer:Since the stress produced on the vegetables by the sharp knife is higher than the blunt knife, vegetables can be cut easily with the sharp knife.4. Why the passengers are advised to remove the ink from their pens while going up in an aeroplane?Answer:When an aero-plane ascends, the atmospheric pressure is decreased. Hence, the ink from the pen will leak out. So that, the passengers are advised to remove the ink from their pens while going up in the aero-plane.5. We use straw to suck soft drinks, why?Answer:When we suck the soft drinks through the straw, the pressure inside the straw becomes less than the atmospheric pressure. Due to the difference in pressure, the soft drink rises in the straw and we are able to enjoy it conveniently.

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