NEET Mechanical Properties of Fluids — Set 9

Question 1

Which of the following statements is correct about viscosity?

Accepted Answer

Viscosity measures a fluid’s resistance to flow due to internal friction between layers, decreasing with temperature in liquids as cohesive forces weaken, not increasing.

Question 2

A hydraulic lift raises a $ 1800 \, \text{kg} $ load using a small piston of radius $ 3 \, \text{cm} $ and a large piston of radius $ 15 \, \text{cm} $. What force is applied on the small piston? (Take $ g = 9.8 \, \text{m/s}^2 $)

Accepted Answer

$ F_1 = \frac{A_1}{A_2} F_2 $, $ F_2 = 1800 \times 9.8 = 17640 \, \text{N} $. $ A_1 = \pi (0.03)^2 $, $ A_2 = \pi (0.15)^2 $, $ \frac{A_1}{A_2} = \frac{0.0009}{0.0225} = \frac{1}{25} $. $ F_1 = \frac{17640}{25} = 705.6 \, \text{N} \approx 706 \, \text{N} $.

Question 3

Why does Bernoulli’s principle not apply to fluids with high viscosity?

Accepted Answer

Bernoulli’s principle assumes no energy loss due to friction, which is valid for non-viscous fluids. High viscosity causes frictional losses between fluid layers, converting kinetic energy into heat, thus violating the energy conservation assumption.

NEET Physics: Mechanical Properties of Fluids — Practice Set 9

Q1. Which of the following statements is correct about viscosity?

Q2. A hydraulic lift raises a \( 1800 \, \text{kg} \) load using a small piston of radius \( 3 \, \text{cm} \) and a large piston of radius \( 15 \, \text{cm} \). What force is applied on the small piston? (Take \( g = 9.8 \, \text{m/s}^2 \))

Q3. Why does Bernoulli’s principle not apply to fluids with high viscosity?

Q4. A plate of area \( 0.07 \, \text{m}^2 \) moves at \( 0.6 \, \text{m/s} \) over a \( 0.9 \, \text{mm} \) thick machine oil film (\( \eta = 0.113 \, \text{Pa s} \)). What force is required?

Q5. Why does atmospheric pressure decrease with altitude?

Q6. What is the gauge pressure at a depth of \( 3.5 \, \text{m} \) in seawater (\( \rho = 1.03 \times 10^3 \, \text{kg/m}^3 \))? (Take \( g = 10 \, \text{m/s}^2 \))

Q7. What is the significance of the term \( \rho g h \) in the pressure equation for a fluid at rest?

Q8. A manometer with seawater (\( \rho = 1.03 \times 10^3 \, \text{kg/m}^3 \)) shows a height difference of \( 0.22 \, \text{m} \). What is the pressure difference? (Take \( g = 9.8 \, \text{m/s}^2 \))

Q9. What is the total pressure at a depth of \( 3.6 \, \text{m} \) in mercury (\( \rho = 13.6 \times 10^3 \, \text{kg/m}^3 \)) with atmospheric pressure \( 1.01 \times 10^5 \, \text{Pa} \)? (Take \( g = 9.8 \, \text{m/s}^2 \))

Q10. Which of the following statements is correct about a liquid drop?

Q11. A pipe’s cross-sectional area changes from \( 0.1 \, \text{m}^2 \) to \( 0.025 \, \text{m}^2 \). If water flows at \( 2.2 \, \text{m/s} \) in the larger section, what is the speed in the smaller section?

Q12. Why does water rise in a capillary tube against gravity?

Q13. A manometer with mercury (\( \rho = 13.6 \times 10^3 \, \text{kg/m}^3 \)) shows a height difference of \( 0.28 \, \text{m} \). What is the pressure difference? (Take \( g = 10 \, \text{m/s}^2 \))

Q14. A pipe narrows from \( 0.06 \, \text{m}^2 \) to \( 0.02 \, \text{m}^2 \). If water flows at \( 1.8 \, \text{m/s} \) in the wider section, what is the speed in the narrower section?

Q15. Why does a spinning ball deviate from a straight path in air, as explained by the Magnus effect?