Tiêu đề TOPIC 5 SINKING AND FLOATING - WazaElimu.com.pdf ✅

38 Solution Data given Weight of the body in air (WA) = 4.9N Weight of the body in liquid (WL) = 3.1N Upthrust =? From; Upthrust = WA – WL Upthrust = 4.9N – 3.1N Upthrust = 1.8N Upthrust acting on the body is 1.8N. QUESTIONS: 1. A body immersed in water displaces 1.1N of the liquid. If its weight while in the water is 3.3N. Find the weight in air. 2. A body weight 3N in air, when it is completely immersed in liquid its weight is 2.2N. Find the upthrust experienced. ARCHIMEDES’ PRINCIPLE It states that: “When a body is partially or totally immersed in a fluid it experiences an upthrust which is equal to the weight of the fluid displaced”. OR “Any object partially or completely immersed in a fluid experiences an upthrust which is equal to the weight of fluid displaced by the body”. NOTE:  Archimedes’ principle is referred to the law of buoyancy. Consider the diagram below which verifies Archimedes’ principle. From the above diagram: The upthrust is equal to the weight of the displaced water. Upthrust does not depend on the shape of the immersed object; it depends on the weight of the displaced fluid.  Archimedes’ principle applies to objects of all densities. DETERMINATION OF RELATIVE DENSITY OF SUBSTANCE BY ARCHIMEDES’ PRINCIPLE
39 Relative densities of the substances (both liquids and solids) can be determined by applying Archimedes’ Principle. A. RELATIVE DENSITY OF A SOLID Consider the diagram below which demonstrates how to determine the relative density of a solid by Archimedes’ Principle. Procedures: 1. Measure the weight of a body in air by using a spring balance and record it as WA 2. Measure the weight of a body when totally immersed in water by using spring balance and record it as WW Results: 1. Weight in air = WA 2. Weight in water (Upthrust) = WA – WW Then: Relative density (R.D) = Weight of a substance in air Weight of the substance in water (Upthrust) Thus; R. D = Weight in air Upthrust R.D = WA WA− WW Example A stone weight 64N in air and 48N when immersed in water. Calculate the: (a) Relative density of the stone (b) Density of the stone in g/cm3 (c) Volume of the stone in cm3 Solution Data given