Ideal fluid The motion of real fluids is very complicated. To understand fluid dynamics in a simpler manner, we assume that the fluid is ideal. An ideal fluid is one which is non-viscous, incompressible, and its flow is steady and irrotational. Thus, an ideal fluid has the following features connected with its flow: (i) Steady … Read more
Critical velocity The critical velocity of a liquid is that limiting value of its velocity of flow upto which the flow is streamlined and above which the flow becomes turbulent. The critical velocity vc of a liquid flowing through a tube depends on (i) coefficient of viscosity of the liquid (η) (ii) density of the … Read more
Laminar flow When the velocity of the flow of a liquid is less than its critical velocity, the liquid flows steadily. Each layer of the liquid slides over the other layer. It behaves as if different lamina are sliding over one another. Such a flow is called laminar flow. The surface obtained by joining the … Read more
Streamline flow When a liquid flow such that each particle of the liquid passing a given point moves along the same path and has the same velocity as its predecessor, the flow is called streamline flow or steady flow. Consider the flow of the liquid along the path ABC; where A, B and C are … Read more
Height of atmosphere For calculating the height of atmosphere, we make use of the following assumptions: (i) The value of g does not change appreciably up to a certain height. (ii) Temperature remains uniform throughout. (iii) Although density of air decreases with height, we assume it to be uniform and take ρ =1.3 kg m-3. … Read more
Atmospheric pressure The gaseous envelope surrounding the earth is called the atmosphere. The pressure exerted by the atmosphere is called atmospheric pressure. The force exerted by air column of air on a unit area of the earth’s surface is equal to the atmospheric pressure. The atmospheric pressure at sea level is 1.013 × 105 Nm-2 … Read more
What is fluid? A fluid is a substance that can flow. It ultimately assumes the shape of the containing vessel because it cannot withstand shearing stress. Thus, both liquids and gases are fluids. Important characteristics of fluids: (i) The atoms or molecules in a fluid are arranged in a random manner. (ii) A fluid cannot … Read more
Cohesive and Adhesive Forces (i) Cohesive force: It is the force of attraction between the molecules of the same substance. Example: Solids have definite shape and size due to strong forces of cohesion amongst their molecules. (ii) Adhesive force: It is the force of attraction between the molecules of two different substances. Example: It is … Read more
It is the maximum distance upto which a molecule can exert some appreciable force of attraction on other molecules. It is of the order of 10″ 9 m in solids and liquids. Sphere of influence. A sphere drawn around a molecule as centre and with a radius equal to the molecular range is called the … Read more
Capillarity The Latin word capilla means hair. A tube of very fine (hair-like) bore is called a capillary tube. When a capillary tube of glass open at both ends is dipped in liquid which wets its walls (e.g., water, alcohol), the liquid rises in the tube. But when the capillary tube is dipped in a … Read more
