Elasticity, Fluid Pressure, Surface Tension and Viscosity

Attempt the quiz above first, then review every question with its correct answer and a short explanation below.

1. Q1.The property by which a body regains its shape after the deforming force is removed is:

   • A.plasticity
   • B.elasticity✓ Correct Answer
   • C.viscosity
   • D.buoyancy

   Explanation: Steel and spring are highly elastic.

2. Q2.Hooke's law states that within the elastic limit:

   • A.stress is inversely proportional to strain
   • B.stress is proportional to strain✓ Correct Answer
   • C.strain is constant
   • D.stress equals strain squared

   Explanation: The constant of proportionality is the modulus of elasticity.

3. Q3.Archimedes' principle is related to:

   • A.surface tension
   • B.viscosity
   • C.elasticity
   • D.buoyant force✓ Correct Answer

   Explanation: A body in a fluid feels an upthrust equal to the weight of fluid displaced.

4. Q4.Small liquid drops are spherical due to:

   • A.viscosity
   • B.buoyancy
   • C.surface tension✓ Correct Answer
   • D.elasticity

   Explanation: A sphere has the least surface area for a given volume.

5. Q5.Viscosity is the property of a fluid that opposes:

   • A.its compression
   • B.its boiling
   • C.relative motion between its layers✓ Correct Answer
   • D.its freezing

   Explanation: Honey is more viscous than water.

6. Q6.A barometer is used to measure:

   • A.atmospheric pressure✓ Correct Answer
   • B.temperature
   • C.humidity
   • D.wind speed

   Explanation: A mercury barometer was invented by Torricelli.

7. Q7.A hydraulic lift works on:

   • A.Archimedes' principle
   • B.Bernoulli's principle
   • C.Hooke's law
   • D.Pascal's law✓ Correct Answer

   Explanation: Pressure applied to a confined fluid is transmitted equally in all directions.

8. Q8.Ice floats on water because:

   • A.it is colder than water
   • B.it is heavier than water
   • C.it has high surface tension
   • D.its density is less than that of water✓ Correct Answer

   Explanation: Water expands on freezing, so ice is about 9 per cent less dense.

9. Q9.Capillary rise of liquids in thin tubes is due to:

   • A.viscosity
   • B.density
   • C.surface tension✓ Correct Answer
   • D.atmospheric pressure alone

   Explanation: Adhesion and surface tension pull liquid up the tube.

10. Q10.The lift of an aeroplane wing is explained by:

    • A.Pascal's law
    • B.Bernoulli's principle✓ Correct Answer
    • C.Hooke's law
    • D.Archimedes' principle

    Explanation: Faster air above the wing means lower pressure there.

11. Q11.Young's modulus is the ratio of:

    • A.volume stress to volume strain
    • B.shear stress to shear strain
    • C.longitudinal stress to longitudinal strain✓ Correct Answer
    • D.force to area

    Explanation: It measures stiffness under stretching or compression.

12. Q12.Adding detergent to water:

    • A.increases its surface tension
    • B.does not change surface tension
    • C.doubles its density
    • D.decreases its surface tension✓ Correct Answer

    Explanation: Lower surface tension lets water wet and penetrate fabrics.

13. Q13.The SI unit of the coefficient of viscosity is:

    • A.pascal-second✓ Correct Answer
    • B.newton per metre
    • C.pascal
    • D.joule per second

    Explanation: In older CGS units the poise is used, where 1 Pa·s = 10 poise.

14. Q14.At sea level, the height of the mercury column in a barometer is about:

    • A.76 cm✓ Correct Answer
    • B.30 cm
    • C.100 cm
    • D.10 cm

    Explanation: This corresponds to one standard atmosphere.

15. Q15.A hydrometer is used to measure the:

    • A.humidity of air
    • B.speed of sound
    • C.atmospheric pressure
    • D.relative density of liquids✓ Correct Answer

    Explanation: It floats higher in denser liquids.

16. Q16.Raindrops fall with a constant terminal velocity because:

    • A.gravity stops acting
    • B.they lose mass
    • C.viscous drag balances their weight✓ Correct Answer
    • D.air pressure is zero

    Explanation: At terminal velocity the net force is zero.

17. Q17.Poisson's ratio is:

    • A.dimensionless✓ Correct Answer
    • B.measured in pascal
    • C.measured in newton
    • D.measured in metre

    Explanation: It is the ratio of lateral strain to longitudinal strain.

18. Q18.Bulk modulus is the ratio of:

    • A.volume stress to volume strain✓ Correct Answer
    • B.longitudinal stress to longitudinal strain
    • C.shear stress to shear strain
    • D.mass to volume

    Explanation: It measures resistance to uniform compression.

19. Q19.The pressure due to a liquid column of height h and density ρ is:

    • A.ρh/g
    • B.ρgh✓ Correct Answer
    • C.ρg/h
    • D.gh/ρ

    Explanation: Pressure grows linearly with depth.

20. Q20.Which of the two is more elastic: steel or rubber?

    • A.rubber
    • B.steel✓ Correct Answer
    • C.both equally
    • D.neither

    Explanation: Steel has a much higher Young's modulus than rubber.