NCERT Class 11 Physics Solutions: Chapter 10 – Mechanical Properties of Fluids-Part 11

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Question 10.24:

During blood transfusion the needle is inserted in a vein where the gauge pressure is . At what height must the blood container be placed so that blood may just enter the vein? [Use the density of whole blood].

Answer:

Gauge pressure,

Density of whole blood,

Acceleration due to gravity,

Height of the blood container

Pressure of the blood container,

The blood may enter the vein if the blood container is kept at a height greater than i.e., about

Question 10.25:

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 velocity of blood flow in an artery of diameter if the flow must remain laminar?

(b) Do the dissipative forces become more important as the fluid velocity increases? Discuss qualitatively.

Answer:

The largest average velocity of blood flow in an artery of diameter if the flow must remain laminar:

Explanation:

Diameter of the artery,

Viscosity of blood,

Density of blood,

Reynolds’ number for laminar flow,

The largest average velocity of blood is given as:

Therefore, the largest average velocity of blood is .

(b) The dissipative forces become more important as the fluid velocity increases: Yes

Explanation:

As the fluid velocity increases, the dissipative forces become more important. This is because of the rise of turbulence. Turbulent flow causes dissipative loss in a fluid.

Question 10.26:

What is the largest average velocity of blood flow in an artery of radius if the flow must remain laminar?

(b) What is the corresponding flow rate? (Take viscosity of blood to be).

Answer:

The largest average velocity of blood:

Explanation:

Radius of the artery,

Diameter of the artery,

Viscosity of blood,

Density of blood,

Reynolds’ number for laminar flow,

The largest average velocity of blood is given by the relation:

Therefore, the largest average velocity of blood is

(b) The corresponding flow rate:

Explanation:

Flow rate is given by the relation:

Therefore, the corresponding flow rate is