CHAPTER NO 1

SOLUTION MANUAL OF HYDRAULICS, FLUID MECHANICS AND HYDRAULIC MACHINES BY R.S. KHURMI

INTRODUCTION

EXERCISE 1.1

1. Determine the mass density of an oil, if 3.0 tones of the oil occupies a volume of 4 m³.

    Sol: Given data:

Mass = m = 3.0 tones                          : - 1 ton = 1,000 Kg

           = 3.0 × 1,000

           = 3,000 Kg

Volume = V = 4m³

Required:

Mass density of oil = ρ =?

We know that;

2. A certain liquid, occupying a volume of 1.6 m³, weight 12.8 KN. What is the Specific weight of the liquid?

Sol: Given data:

Volume = V = 1.6 m³

Weight = W = 12.8 KN

3. A container of volume 3.0 m³ has 25.5 KN of an oil. Find the specific weight and mass density of the oil.

Sol: Given data:

Volume = V = 3.0 m³

Weight = W = 25.5 KN

Required:

4. What is the specific gravity of a liquid, whose specific weight is 7.36 KN/m³?

Sol: Given data:

Required:

Specific Gravity = Sp. gr =?

We know that;

5. A drum 0f 1 m³ volume contains 8.5 KN an oil when full. Find its Specific weight and specific gravity.

Sol: Given data:

Volume = V = 1 m³

Weight = w = 8.5 KN

Required:

QUESTIONS

1. Define the density of a liquid?

Ans: The density or mass density of a liquid may be define as ; the ratio of mass of fluid to its volume at a standard temperature and pressure. Thus mass per unit volume is called density. It is denoted by ρ (rho). The SI unit of mass density is Kg/m³ (Kilogram per Cubic meter).

Mathematically, mass density as;

The density of water is 1 g/cm³ or 1,000 Kg/m³or 1.94 Slug/ft³.

2. Differentiate b/w Specific Weight and Specific Gravity of an oil.

Ans: Specific weight of oil:

The specific weight or weight density of a liquid may be defined as it is the ratio b/w the weight of fluid to its volume. Thus weight per unit volume of fluid is called Specific weight or weight density and it is denoted by γ.The SI unit of Specific weight is KN/m³.

Mathematically; 

• Different oil’s having different Specific weight.

Specific Gravity of oil:

Specific gravity is defined as, the ratio of Specific weight of Liquid to the Specific weight of a standard fluid. For liquids the standard fluid is taken water and for gases, the standard fluid is taken air. Specific gravity is also called relative density. It is dimensionless quantity and it is denoted by the symbol S or (briefly written as Sp. gr).

Mathematically;

For liquids;

Note: If density of a liquid is in ton per m³ (t/m³), it is numerically equal to specific gravity of the liquid.

3 .What is the ratio b/w Specific weight and mass density of a liquid?

Ans: we know that;

4.  Distinguish b/w compressibility and capillarity of water?

Ans:

Compressibility of water:

         It is defined as; if the density or volume changes with the changes of pressure then the fluids are called compressible fluids. The SI unit is N/m³.

         The variation in the volume of water, with the variation of pressure is so small that for all practical purposes it is neglected. Thus, the water is considered to be in-compressible liquid.

Capillarity of water:

          Capillarity is defined as; the rise or fall of liquid in a small glass tube due to cohesion and adhesion is called the Capillarity or capillary rise. The SI unit is m (meter).

          When a glass tube of small diameter is dipped in water, the water rises up in the tube with an upward concave surface. This is due to reason that the adhesion (b/w the tube and water molecules) is more than the cohesion b/w the water molecules.

          The phenomenon of rising water in the tube of smaller diameter is called the capillary rise.

5. What role does the surface tension of liquid play, when a glass tube of small diameter is dipped into it?

Ans: The surface tension of a liquid is its property, which enables it to resist tensile stress.

OR

The cohesive forces b/w the liquid molecules are responsible for the phenomenon known as surface tension.

When a glass tube of small diameter is dipped in water, the water rises up in the tube with an upward concave surface. This is due to reason that the adhesion (b/w the tube and water molecules) is more than the cohesion b/w the water molecules.

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Posted in: By R.S. Khurmi