back to directory
NEET PHYSICSMechanical Properties of FluidMedium

Question

Two small spherical metal balls, having equal masses, are made from materials of densities ρ1\rho_1 and ρ2\rho_2 such that ρ1=8ρ2\rho_1 = 8\rho_2 and having radii of 1 mm1 \text{ mm} and 2 mm2 \text{ mm}, respectively. They are made to fall vertically (from rest) in a viscous medium whose coefficient of viscosity equals η\eta and whose density is 0.1ρ20.1\rho_2. The ratio of their terminal velocities would be:

A

\frac{79}{72}

B

\frac{19}{36}

C

\frac{39}{72}

D

\frac{79}{36}

Step-by-Step Solution

  1. Terminal Velocity Formula: The terminal velocity (vtv_t) of a spherical body falling through a viscous fluid is given by Stokes' Law: vt=2r2(ρσ)g9ηv_t = \frac{2r^2 (\rho - \sigma)g}{9\eta} where rr is the radius of the sphere, ρ\rho is the density of the sphere, σ\sigma is the density of the fluid, and η\eta is the coefficient of viscosity .
  2. Parameters for Ball 1:
  • Radius r1=1 mmr_1 = 1 \text{ mm}
  • Density ρ1=8ρ2\rho_1 = 8\rho_2
  • Fluid density σ=0.1ρ2\sigma = 0.1\rho_2 v1r12(ρ1σ)=(1)2(8ρ20.1ρ2)=7.9ρ2v_1 \propto r_1^2 (\rho_1 - \sigma) = (1)^2 (8\rho_2 - 0.1\rho_2) = 7.9\rho_2
  1. Parameters for Ball 2:
  • Radius r2=2 mmr_2 = 2 \text{ mm}
  • Density ρ2=ρ2\rho_2 = \rho_2
  • Fluid density σ=0.1ρ2\sigma = 0.1\rho_2 v2r22(ρ2σ)=(2)2(ρ20.1ρ2)=4(0.9ρ2)=3.6ρ2v_2 \propto r_2^2 (\rho_2 - \sigma) = (2)^2 (\rho_2 - 0.1\rho_2) = 4(0.9\rho_2) = 3.6\rho_2
  1. Calculate Ratio: v1v2=7.9ρ23.6ρ2=7936\frac{v_1}{v_2} = \frac{7.9\rho_2}{3.6\rho_2} = \frac{79}{36}

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Mechanical Properties of Fluid. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSMechanical Properties of Fluidsphericalhavingmassesmaterialsdensities

More Mechanical Properties of Fluid Questions

View all

A rectangular film of liquid is extended from $(4 \text{ cm} \times 2 \text{ cm})$ to $(5 \text{ cm} \times 4 \text{ cm})$. If the work done is $3 \times 10^{-4} \text{ J}$, then the value of the surface tension of the liquid is:

A.$0.250 \text{ Nm}^{-1}$
B.$0.125 \text{ Nm}^{-1}$
C.$0.2 \text{ Nm}^{-1}$
D.$8.0 \text{ Nm}^{-1}$
EasySolve

A small hole of an area of cross-section $2 \text{ mm}^2$ is present near the bottom of a fully filled open tank of height $2 \text{ m}$. Taking $g = 10 \text{ m/s}^2$, the rate of flow of water through the open hole would be nearly:

A.$6.4 \times 10^{-6} \text{ m}^3/\text{s}$
B.$12.6 \times 10^{-6} \text{ m}^3/\text{s}$
C.$8.9 \times 10^{-6} \text{ m}^3/\text{s}$
D.$2.23 \times 10^{-6} \text{ m}^3/\text{s}$
EasySolve

In a U-tube, as shown in the figure, the water and oil are in the left side and right side of the tube respectively. The height of the water and oil columns are 15 cm and 20 cm respectively. The density of the oil is: [take ρ_water = 1000 kg/m^3]

A.1200 kg/m^3
B.750 kg/m^3
C.1000 kg/m^3
D.1333 kg/m^3
EasySolve

A U-tube with both ends open to the atmosphere is partially filled with water. Oil, which is immiscible with water, is poured into one side until it stands at a distance of $10 \text{ mm}$ above the water level on the other side. Meanwhile, the water rises by $65 \text{ mm}$ from its original level (see diagram). The density of the oil is:

A.$650 \text{ kg m}^{-3}$
B.$425 \text{ kg m}^{-3}$
C.$800 \text{ kg m}^{-3}$
D.$928 \text{ kg m}^{-3}$
MediumSolve

Which of the following statements is not true?

A.The coefficient of viscosity is a scalar quantity.
B.Surface tension is a scalar quantity.
C.Pressure is a vector quantity.
D.Relative density is a scalar quantity.
EasySolve

The heart of a man pumps $5 \text{ L}$ of blood through the arteries per minute at a pressure of $150 \text{ mm}$ of mercury. If the density of mercury is $13.6 \times 10^3 \text{ kg/m}^3$ and $g = 10 \text{ m/s}^2$, then the power of heart in watt is:

A.1.7
B.2.35
C.3
D.1.5
MediumSolve

Water rises to a height $h$ in a capillary tube. If the length of the capillary tube above the surface of water is made less than $h$, then:

A.water rises upto the tip of capillary tube and then starts overflowing like a fountain
B.water rises upto the top of capillary tube and stays there without overflowing
C.water rises upto a point a little below the top and stays there
D.water does not rise at all
EasySolve

A liquid does not wet the solid surface if the angle of contact is:

A.equal to 45°
B.equal to 60°
C.greater than 90°
D.zero
EasySolve

This neet physics practice question is part of the TopperSquare free question bank. TopperSquare offers 15,000+ chapter-wise NEET MCQs across Physics, Chemistry, and Biology with detailed step-by-step explanations, full mock tests, NEET PYQs (2010–2024), and an AI-powered performance analytics dashboard. browse all neet practice questions → · practice physics sets →