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State Of Matter

📆 December 5, 2024

Total Questions: 27

11. Bubbles of air rise up through liquids due to: [S.S.C. Online Graduation Level (T-I) 27.08.2016 (Shift-I)]

Correct Answer: (b) viscosity and buoyancy.
Solution:Due to the force of buoyancy and attraction, the velocity of rise of bubbles in the liquid increases.
  • This force depends strongly on the properties, gravity and diameter of the fluid. As a result, the growth of the bubble depends strongly on the terminal velocity as well as the speed of the viscosity effect.
  • So it is clear that option (b) will be the required answer.

12. What is the viscosity of an ideal fluid? [S.S.C. Online CHSL (T-I) 17.01.2017 (Shift-I)]

Correct Answer: (c) Zero
Solution:The viscosity of an ideal fluid is zero. An ideal fluid is a theoretical concept used in fluid mechanics.

It's defined as:

  • Incompressible (its density doesn’t change)
  • No viscosity (it offers no resistance to shear stress)
  • Irrotational (no turbulence or eddies)
  • No heat conduction
    Because it has zero viscosity, an ideal fluid flows without any internal friction — meaning layers of fluid slide over each other effortlessly.

Of course, in the real world, all fluids have some viscosity, but the concept of an ideal fluid helps simplify problems in physics and engineering.

13. Which among the following is false about viscosity? [S.S.C. Online CHSL (T-I) 24.01.2017 (Shift-III)]

Correct Answer: (d) Viscosity of liquid decreases with an increase in pressure.
Solution:Mostly all liquids are non-compressible i.e. at low and medium pressures, there is no significant reduction in the volume of liquids due to pressure. Therefore, there is no effect on the viscosity of the liquid.

14. What is the instrument used for measuring the speed and rate of flow of a fluid flowing in a pipe? [S.S.C. Online CHSL (T-I) 16.04.2021 (Shift-III)]

Correct Answer: (d) Venturimeter
Solution:Venturimeter is a type of flowmeter that works on the principle of Bernoulli's Equation.
  • A Venturimeter is a device used for measuring the rate of flow of fluid of a liquid flowing through a pipe.
  • The venturi meter always has a smaller convergent portion and a larger divergent portion.
  • The size of the venturi meter is specified by its pipe diameter as well as throat diameter.

15. What is the cause of surface tension in a liquid? [S.S.C. Online Stenographer 14.09.2017 (Shift-II)]

Correct Answer: (b) Cohesive force between molecules
Solution:Molecules inside the liquid are attracted by the molecules near them due to cohesive force.

Surface tension is a characteristic property of the surface of a liquid.

  • Due to surface tension, the surface of liquids exhibits a kind of elastic property.

Hence option (b) will be the correct answer.

16. The force of attraction between molecules of the same substance is called ________ . . [S.S.C. Online CGL (T-I) 24.08.2021 (Shift-I)]

Correct Answer: (c) cohesive force
Solution:The force of attraction between the same molecules is called the force of cohesion.

The force of attraction between different types of molecules is called the force of adhesion.

17. AV = constant, where A = area of cross-section and v = velocity of fluid. This equation is called ______. [S.S.C. Online CHSL (T-I) 21.01.2017 (Shift-I)]

Correct Answer: (b) Equation of continuity
Solution:

The Continuity Equation comes from the principle of conservation of mass for an incompressible fluid (one whose density doesn’t change).

  • It states that the mass flow rate must remain constant from one cross-section of a pipe to another.
  • So, if the pipe narrows (smaller A), the fluid must speed up (larger V), and vice versa.
  • A1​V1​=A2​V2​=constant
  • This is super useful in fluid dynamics — especially when analyzing flow through nozzles, pipes, or channels.

18. On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because of________. [S.S.C. Online Graduation Level (T-I) 27.08.2016 (Shift-III)]

Correct Answer: (c) Cohesion of mercury is greater than its adhesion with glass.
Solution:On a clean glass plate, a drop of water spreads out while a drop of mercury stays almost spherical because of surface tension and adhesion.

The reason is the difference in cohesive and adhesive forces:

  • Water has strong adhesive forces with glass (it "likes" sticking to the glass), and its surface tension is lower than mercury's. So it spreads out to increase contact.
  • Mercury has very strong cohesive forces (its molecules strongly attract each other) and weak adhesion to glass. Because of its high surface tension, it minimizes surface area and forms a nearly spherical shape.

19. If ice floating on water in a vessel melts, the water level in the vessel________. [S.S.C. Online CHSL (T-I) 16.01.2017 (Shift-III)]

Correct Answer: (b) does not change
Solution:

  • If ice floating on water in a vessel melts, the water level in the vessel remains the same.

    Explanation:

    Ice displaces an amount of water equal to its weight while floating. When it melts, it turns into water of the same weight. Hence, the volume of water added by the melted ice exactly equals the volume of water it had displaced while floating.

    So, there is no change in water level.

20. What will change in the water level in a vessel when a piece of ice floating in it melts? [S.S.C. Online C.P.O.S.I. (T-I) 2.07.2017 (Shift-I)]

Correct Answer: (c) will remain the same
Solution:
  • Floating ice displaces an amount of water equal to its own weight.
  • When it melts, it turns into water of the same mass.
  • The volume of that melted water exactly equals the volume of water the ice was displacing when it was floating.
    So, there's no net change in the water level.
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