## It is known that density ρ of air decreases with height y as ρ0e-y/y0 Where ρ0 = 1.25 kg m-3 is the density at sea level, and y0 is a constant. This density variation is called the law of atmospheres. Obtain this law assuming that the temperature of atmosphere remains a constant (isothermal conditions). Also assume that the value of gremains constant. (b) A large He balloon of volume 1425 m3 is used to lift a payload of 400 kg. Assume that the balloon maintains constant radius as it rises. How high does it rise? | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-10 Mechanical Properties of Fluids

Q.31:- (a)It is known that density ρ of air decreases with height y as ρ0e-y/y0 Where ρ0 = 1.25 kg m-3 is the density at sea level, and y0 is a constant. This density variation is called…

## Two narrow bores of diameters 3.0 mm and 6.0 mm are joined together to form a U-tube open at both ends. If the U-tube contains water, what is the difference in its levels in the two limbs of the tube? Surface tension of water at the temperature of the experiment is 7.3 × 10–2 N m–1. Take the angle of contact to be zero and density of water to be 1.0 × 103 kg m–3 (g = 9.8 m s–2). | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-10 Mechanical Properties of Fluids

Q.30:- Two narrow bores of diameters 3.0 mm and 6.0 mm are joined together to form a U-tube open at both ends. If the U-tube contains water, what is the difference…

## Mercury has an angle of contact equal to 140° with soda lime glass. A narrow tube of radius 1.00 mm made of this glass is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside? Surface tension of mercury at the temperature of the experiment is 0.465 N m–1. Density of mercury = 13.6 × 103 kg m–3. | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-10 Mechanical Properties of Fluids

Q.29:- Mercury has an angle of contact equal to 140° with soda lime glass. A narrow tube of radius 1.00 mm made of this glass is dipped in a trough containing…

## Answer Terminal speed = 5.8 cm/s Viscous force = 3.9 × 10–10 N Radius of the given uncharged drop, r = 2.0 × 10–5 m Density of the uncharged drop, ρ = 1.2 × 103 kg m–3 Viscosity of air, η = 1.8 × 10-5 Pa s Density of air (ρ0) can be taken as zero in order to neglect buoyancy of air. Acceleration due to gravity, g = 9.8 m/s2 Terminal velocity (v) is given by the relation: v = 2r2 × (ρ – ρ0) g / 9η = 2 × (2 × 10-5)2 (1.2 × 103 – 0 ) × 9.8 / (9 × 1.8 × 10-5) = 5.8 × 10-2 m/s = 5.8 cm s-1 Hence, the terminal speed of the drop is 5.8 cm s–1. The viscous force on the drop is given by: F = 6πηrv ∴ F = 6 × 3.14 × 1.8 × 10-5 × 2 × 10-5 × 5.8 × 10-2 = 3.9 × 10-10 N Hence, the viscous force on the drop is 3.9 × 10–10 N. | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-10 Mechanical Properties of Fluids

Q.29:- In Millikan’s oil drop experiment, what is the terminal speed of an uncharged drop of radius 2.0 × 10–5 m and density 1.2 × 103 kg m–3? Take the viscosity of air…

## A plane is in level flight at constant speed and each of its two wings has an area of 25 m2. If the speed of the air is 180 km/h over the lower wing and 234 km/h over the upper wing surface, determine the plane’s mass. | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-10 Mechanical Properties of Fluids

Q.27:- A plane is in level flight at constant speed and each of its two wings has an area of 25 m2. If the speed of the air is 180 km/h…

## What is the largest average velocity of blood flow in an artery of radius 2 × 10–3 m if the flow must remain laminar? (b) What is the corresponding flow rate? | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-10 Mechanical Properties of Fluids

Q.26:- (a)What is the largest average velocity of blood flow in an artery of radius 2 × 10–3 m if the flow must remain laminar? (b) What is the corresponding flow…

## In deriving Bernoulli’s equation, we equated the work done on the fluid in the tube to its change in the potential and kinetic energy. (a) What is the largest average velocity of blood flow in an artery of diameter 2 × 10–3 m if the flow must remain laminar? (b) Do the dissipative forces become more important as the fluid velocity increases? Discuss qualitatively. | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-10 Mechanical Properties of Fluids

Q.25:- In deriving Bernoulli’s equation, we equated the work done on the fluid in the tube to its change in the potential and kinetic energy. (a) What is the largest average…

## During blood transfusion the needle is inserted in a vein where the gauge pressure is 2000 Pa. At what height must the blood container be placed so that blood may just enter the vein? | Learn NCERT solution | Education portal Class 11 Physics | Study online Unit-10 Mechanical Properties of Fluids

Q.24:- During blood transfusion the needle is inserted in a vein where the gauge pressure is 2000 Pa. At what height must the blood container be placed so that blood may…