121.

Viscous force exerted by the liquid flowing between two plates in a streamline flow depends upon the

• velocity gradient in the direction perpendicular to the plates

• area of plate

• co-efficient of viscosity of the liquid

• all of these

Assertion: When height of a tube is less than liquid rise in the capillary tube, the liquid does not overflow. 

Reason: Product of radius of meniscus and height of liquid in the capillary tube always remain constant.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• f both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

A spherical body of diameter D is falling in viscous medium. Its terminal velocity is proportional to

• V_t ∝ D^1/2

• V_t ∝ D^3/2

• V_t ∝ D²

• V_t ∝ D^5/2

Assertion:  Surface energy of an oil drop is same whether placed on glass or water surface. 

Reason:  Surface energy is dependent only on the properties of oil.

• If both assertion and reason are true and reason is the correct explanation of assertion.
  
  

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  Turbulence is always dissipative. 

Reason: High reynold number promotes turbulence.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Pressure head in Bernoulli's equation is

• $\frac{\mathrm{P} \mathrm{\rho }}{\mathrm{g}}$

• $\frac{\mathrm{P}}{\mathrm{\rho } \mathrm{g}}$

• ρ g

• Pρg

Two spherical soap bubbles of radii a and b in vacuum coaleasce under isothermal conditions. The resulting bubbles has a radius given by

• $\frac{\left(\mathrm{a} + \mathrm{b}\right)}{2}$

• $\frac{\mathrm{ab}}{\mathrm{a} + \mathrm{b}}$

• $\sqrt{{\mathrm{a}}^2 + {\mathrm{b}}^2}$

• a+ b

A liquid is kept in a cylindrical vessel which is being rotated about a vertical axis through the centre of the circular base. If the radius of the vessel is r and angular velocity of rotation is w, then the difference in the heights of the liquid at the centre of the vessel and the edge is

• $\frac{\mathrm{r} \mathrm{\omega }}{2 \mathrm{g}}$

• $\frac{{\mathrm{r}}^2 {\mathrm{\omega }}^2}{2 \mathrm{g}}$

• $\sqrt{2 \mathrm{gr} \mathrm{\omega }}$

• $\frac{{\mathrm{\omega }}^2}{2 {\mathrm{gr}}^2}$

A capillary tube of radius r is immersed in water and water rises in it to a height h. The mass of water in the capillary tube is 5 g. Another capillary tube of radius 2 r is immersed in water. The mass of water that will rise in this tube is

• 2.5 g

• 5.0 g

• 10 g

• 20 g

Neglecting  the  density  of  air, the  thermal  velocity  obtained  by  a  raindrop  of  radius  0.3  nm  falling  through  air  of  viscosity  1.8 × 10⁵ N s m²  will  be

• 10.9 m s^-1

• 7.48  m s^-1

• 3.7 m s^-1

• 12.8 m s^-1