Understanding Archimedes’s Principle: Buoyancy and Everyday Applications

Understanding Archimedes’s Principle: Buoyancy and Everyday Applications

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  Archimedes’s Principle Marianne MaeM. Flores, LPT
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  Introduction ▪ Archimedes’s principleexplains why objects float or sink. ▪ At home, these principles appear in everyday contexts like water tanks, hydraulic jacks, and even simple experiments such as the Cartesian diver.
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  Core Idea ofArchimedes’s Principle ▪ Buoyant force: Upward force exerted by a fluid on an immersed object. ▪ Displaced fluid: The volume of fluid pushed aside by the object. ▪ Condition for floating: –If buoyant force = object’s weight, the object floats at equilibrium. –If buoyant force > object’s weight, the object rises. –If buoyant force < object’s weight, the object sinks.
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  Applications of Archimedes’ s Principleat Home
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  Floating Objects ▪ anobject floats when the buoyant force (equal to the weight of displaced fluid) balances or exceeds its own weight. If the buoyant force is less, the object sinks. ▪ Plastic bottles, wooden toys, or cooking utensils float in water because the buoyant force equals the weight of displaced water.
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  Everyday Examples ofFloating ▪ Wooden blocks: Wood floats because its density is lower than water, so the displaced water weighs more than the block. ▪ Ships: Even though ships are massive, their hulls are designed to displace enough water to balance their weight. ▪ Human body: In swimming pools, people float more easily when they stretch out, because they displace more water. ▪ Ice cubes: Ice floats in water since frozen water is less dense than liquid water.
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  Formula for BuoyantForce This formula shows why larger volume or lower density objects float more easily. Note: g is constant 9.8 m/s²
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  Example 1: WoodenBlock in Water ▪ G- Block volume: 0.02 m³ Water density: 1000 kg/m³ ▪ Acceleration due to gravity: 9.8m/s² ▪ R- Buoyant force ▪ E- Fb=pVg ▪ S- Fb=(1000 kg/m³) (0.02 m³) (9.8m/s²) ▪ A- Fb= 196 N. Interpretation: The buoyant force is 196 N. If the block’s weight is less than this, it floats.
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  Example 2: BoatHull ▪ G- Hull displaces: 3 m³ Water density: 1000 kg/m³ ▪ Acceleration due to gravity: 9.8m/s² ▪ R- Buoyant force ▪ E- Fb=pVg ▪ S- Fb=(1000 kg/m³) (3 m³) (9.8m/s²) ▪ A- Fb= 29,400 N. Interpretation: The buoyant force is 29,400 N. The boat can support up to 29,400 N ( 3,000 kg) before sinking deeper. ≈
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  Try this! ▪ IceCube Floating Given:Ice cube volume = 0.001 m³ Water density = 1000 kg/m³ ▪ Human Body in Pool Given:Body volume = 0.07 m³ Water density = 1000 kg/m³
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  Life Jackets ▪ Air-filledjackets increase volume without adding much weight, displacing more water and keeping a person afloat. ▪ When a person wearing a life jacket enters water, the jacket displaces a large volume of water. ▪ Life jackets are filled with air pockets or foam, which are much less dense than water. ▪ The displaced water weighs more than the combined weight of the person and the jacket, creating an upward buoyant force that keeps them afloat.
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  Everyday Impact ▪ Safetyin swimming: Even non-swimmers can stay afloat because the buoyant force counteracts their body weight. ▪ Boating and fishing: Life jackets provide security in case of accidental falls into water. ▪ Emergency survival: In floods or shipwrecks, they prevent drowning by ensuring the head stays above water.
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  Hydrometers ▪ Used inkitchens or home brewing, they measure liquid density by floating at different levels depending on the fluid’s density. ▪ A hydrometer is a classic application of Archimedes’ principle, used to measure the density (or specific gravity) of liquids.
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  How it works? ▪Floating mechanism: A hydrometer floats in a liquid, and the depth to which it sinks depends on the liquid’s density. ▪ Displaced liquid: According to Archimedes’ principle, the buoyant force equals the weight of displaced liquid. ▪ Balance of forces: The hydrometer sinks until the buoyant force equals its own weight. ▪ Density reading: The scale on the stem shows the liquid’s density at the level where the hydrometer floats.
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  Everyday Applications ▪ Homebrewing: Used to measure sugar content in wine or beer to track fermentation. ▪ Battery testing: Measures the density of electrolyte solution in car batteries to check charge levels. ▪ Milk testing: Detects adulteration by measuring density differences. ▪ Aquarium care: Ensures proper salinity in saltwater aquariums.
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  Swimming Pools ▪ Whenyou step into a pool, you feel lighter because water exerts an upward buoyant force. ▪ Buoyant force: When you enter the pool, your body displaces water. The displaced water pushes back with an upward force. ▪ Balance of forces: If the buoyant force equals your weight, you float. If it’s less, you sink. ▪ Density factor: Human bodies are close in density to water, so small changes (like filling lungs with air) make floating easier.
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  Everyday Observation ▪ Floatingon your back: Expanding your chest with air increases volume, displacing more water, so you rise. ▪ Children with floaters: Floatation devices add volume without much weight, increasing buoyancy. ▪ Diving vs. floating: When you dive, you sink until the buoyant force balances your weight; when you relax, you float near the surface.