Physics Keypoints: Liquids At Rest; The behavior of liquids at rest and the physical properties of substances immersed in them are governed by fundamental principles of physics. This article explores key concepts related to density, relative density, upthrust, and Archimedes’ principle. Understanding these principles is crucial in various scientific and engineering applications.
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Physics Keypoints: Liquids At Rest
(i) Determination of Density of Solids and Liquids:
Density is a measure of how much mass is contained in a given volume of a substance. It is typically expressed in units such as kilograms per cubic meter (kg/m³) or grams per cubic centimeter (g/cm³). The density of a solid or liquid can be determined by measuring its mass and volume and using the formula:
(ii) Definition of Relative Density:
Relative density, also known as specific gravity, is the ratio of the density of a substance to the density of a reference substance, often water. It is a dimensionless quantity and can be calculated using the formula:
(iii) Upthrust on a Body Immersed in a Liquid:
When an object is immersed in a liquid, it experiences an upward force called upthrust or buoyant force. This force is a result of the pressure difference between the top and bottom of the submerged object and is equal to the weight of the displaced liquid.
(iv) Archimedes’ Principle and Law of Floatation:
Archimedes’ principle states that any object partially or wholly submerged in a fluid experiences an upthrust equal to the weight of the fluid displaced by the object. This principle is crucial in understanding the behavior of floating and sinking objects.
The law of floatation, a direct consequence of Archimedes’ principle, states that a floating object displaces its weight of the liquid it is in. This principle explains why some objects float while others sink in a liquid.
Applications, e.g., Ships and Hydrometers:
- Ships: The design and buoyancy of ships are based on Archimedes’ principle. The weight of the ship must be less than the weight of the water it displaces to ensure it floats. Ballast tanks are used to control the ship’s buoyancy and stability.
- Hydrometers: A hydrometer is an instrument used to measure the relative density (specific gravity) of liquids. It works on the principle that the buoyant force on the hydrometer in a liquid is proportional to the liquid’s density. Hydrometers are commonly used in industries like winemaking, brewing, and automotive maintenance.
Conclusion:
Understanding the principles of density, relative density, upthrust, and Archimedes’ principle is essential in various scientific and practical applications. These concepts help explain why objects float or sink in liquids, how ships stay afloat, and how instruments like hydrometers are used to determine the properties of liquids.
Whether you are designing a ship or analyzing the quality of a liquid, these fundamental principles play a crucial role in our understanding of liquids at rest.
