Fluid Statics_Short Questions_Class 12 Physics скачать в хорошем качестве

Fluid Statics_Short Questions_Class 12 Physics

In this video you will learn important short answer questions related to chapter Fluid Statics of Class 12. 1. In a hot air ballooning, a large balloon is filled with air heated by a gas burner at the bottom, why must the air be heated? When the air is heated, the density of air decreases and volume increases. So, it displaces the large amount of air and gets sufficient upthrust to lift it up. Therefore, the air is heated to let the balloon up in the sky Fluid Mechanics Short Answer QuestionsClass XII Physics 2 / 42 2. Steel balls sink in water but they don’t sink in mercury. Why? The density of steel is higher than water but smaller than mercury. When steel balls are dipped in water, they sink because upthrust due to water is less than the weight of the steel balls. But steel balls don’t sink in mercury because upthrust due to mercury is higher than the weight of the steel balls. Fluid Mechanics Short Answer QuestionsClass XII Physics 3 / 42 3.Does a ship sink more in river water or in sea water? Since, density of sea water is greater than that of fresh water. So same upthrust is achieved in sea by the displacement of smaller volume than in fresh water. Hence, depth of immersion of a ship is less in sea than in fresh water. Fluid Mechanics Short Answer QuestionsClass XII Physics 4 / 42 4.An ice cube floats in a glass of water. When the ice melts, will the water level in the glass rise, fall or remain unchanged? The water level remains unchanged. The ice cube displaces a weight of water equal to its own weight. When the ice cube melts, the volume of water produced equals the volume of water, it displaced when frozen. Fluid Mechanics Short Answer QuestionsClass XII Physics 5 / 42 5.What is centre of buoyancy? Centre of buoyancy is the C.G. of displaced liquid by the immersion of a body inside the liquid. The Upthrust (force of buoyancy) acts upward through centre of buoyancy on immersed body. Fluid Mechanics Short Answer QuestionsClass XII Physics 6 / 42 6. Why does ice float in water? For a body to float, the density of body should be less than the density of liquid. Here, the density of ice is less than the density of water. So, ice floats in water. Fluid Mechanics Short Answer QuestionsClass XII Physics 7 / 42 7. It is difficult to stop bleeding from a cut in human body at high altitudes, why? The atmospheric pressure is low at high altitudes. Due to greater pressure difference between atmospheric pressure and blood pressure, it is difficult to stop bleeding from a cut in human body Fluid Mechanics Short Answer QuestionsClass XII Physics 8 / 42 8. A helium filled balloon rises to a certain height and then halts. Why? Since, the density of helium gas is lower than that of air near the ground. The weight of the balloon will be smaller than the upthrust and the balloon rises to a certain height. It halts at a certain height when upthrust is equal to its weight (where the density of air and helium becomes same). Fluid Mechanics Short Answer QuestionsClass XII Physics 9 / 42 9. A cork is floating in water. What is the apparent weight of the cork? A body can float in water if the weight of body is equal to upthrust acting on it. The centre of gravity of the body and the centre of buoyancy of displaced water lie in the same line. Thus, the cork becomes weightless (apparent weight becomes zero). Fluid Mechanics Short Answer QuestionsClass XII Physics 10 / 42 10. Why is the bottom of a ship made heavy? For the stable equilibrium, the meta-centre must lie above the centre of gravity for a floating body. When the bottom of the ship is made heavy, the centre of gravity lies lower than meta-centre Fluid Mechanics Short Answer QuestionsClass XII Physics 11 / 42 11.Does the Archimedes’ principle hold in vessel in free fall? No, the vessel in free fall is in a state of weightlessness i.e., the apparent value of g is zero and hence, the buoyant force does not exist. So, Archimedes principle does not hold good Fluid Mechanics Short Answer QuestionsClass XII Physics 12 / 42 12. What is cohesive force? The force of attraction between the molecules of the same substance is called force of cohesion or cohesive force. It is maximum in solids, lesser in liquids and the least in gases. Fluid Mechanics Short Answer QuestionsClass XII Physics 13 / 42 13. What is adhesive force? The force of attraction between the molecules of the different substances is called the force of adhesion or adhesive force. Force of adhesion is different for different substances. For example, gum has greater adhesive force for a solid surface than water