Q 11 :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: A spherical body of radius $(5\pm 0.1)$ mm having a particular density is falling through a liquid of constant density. The percentage error in the calculation of its terminal velocity is 4%.

Reason R: The terminal velocity of the spherical body falling through the liquid is inversely proportional to its radius.

In the light of the above statements, choose the correct answer from the options given below          [2023]

• Both A and R are true but R is NOT the correct explanation of A

   

• Both A and R are true and R is the correct explanation of A

   

• A is false but R is true

   

• A is true but R is false

   

Q 12 :

A spherical ball of radius 1 mm and density 10.5 g/cc is dropped in glycerine of coefficient of viscosity 9.8 poise and density 1.5 g/cc. The viscous force on the ball when it attains constant velocity is $3696\times {10}^{-x}\text{\hspace{0.05em}N}$. The value of $x$ is. (Given: $g=9.8{\text{\hspace{0.05em}m/s}}^2$ and $\pi =\frac{22}{7}$) ________ .           [2023]

Q 13 :

A metal block of base area $0.20{\text{\hspace{0.05em}m}}^2$ is placed on a table, as shown in the figure. A liquid film of thickness 0.25 mm is inserted between the block and the table. The block is pushed by a horizontal force of 0.1 N and moves with a constant speed. If the viscosity of the liquid is $5.0\times {10}^{-3}$ poiseuille, the speed of the block is _______ $\times {10}^{-3}\text{\hspace{0.05em}m/s}$.        [2023]

Q 14 :

An air bubble of diameter 6 mm rises steadily through a solution of density $1750{\text{\hspace{0.05em}kg/m}}^3$ at the rate of 0.35 cm/s. The coefficient of viscosity of the solution (neglect density of air) is _______ P as (given, $g=10{\text{\hspace{0.05em}ms}}^{-2}$).                    [2023]