{"id":153088,"date":"2022-04-29T12:30:18","date_gmt":"2022-04-29T07:00:18","guid":{"rendered":"https:\/\/www.aakash.ac.in\/blog\/?p=153088"},"modified":"2023-04-04T22:55:32","modified_gmt":"2023-04-04T17:25:32","slug":"what-is-buoyancy-concept-note-for-cbse-class-9-physics","status":"publish","type":"post","link":"https:\/\/www.aakash.ac.in\/blog\/what-is-buoyancy-concept-note-for-cbse-class-9-physics\/","title":{"rendered":"What is buoyancy? Concept note for CBSE Class 9 Physics"},"content":{"rendered":"<p><span style=\"font-weight: 400;\">How do objects float in a fluid? The answer to this question is &#8216;buoyancy&#8217;. A buoyant force is a type of force that occurs in all gases and fluids. This force acts in an upward direction due to the presence of gravity. It is exerted opposite to the gravitational force. The buoyant force is found immersed in any object. Buoyancy can result from the pressure differences that act on an object&#8217;s opposite sides, which can be seen in a static fluid.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In this article, let us learn everything related to buoyancy and its other related concepts in detail, which will benefit the CBSE Class 9 students to obtain good marks in their Physics board exam.<\/span><\/p>\n<h3>Buoyant force<\/h3>\n<p><span style=\"font-weight: 400;\">In Physics, the buoyant force is a force that is exerted on an object which is partially or completely immersed in a fluid. The other name for this upward force is called upthrust. Because of the presence of buoyant force, a body that is submerged fully or partly in a fluid will lose its weight. In simple terms, it will appear to be lighter.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">There are a few factors of buoyant force. The following are some of them:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">The volume of the displaced fluid<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">The density of the fluid<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Local acceleration due to the presence of gravity<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">An object will tend to sink if its density is greater than the fluid it has been immersed in. An object would float if its density is lesser than the density of the fluid or the liquid is appropriately shaped. For example, a boat floating in the sea could be considered in this case. A boat is a solid object with a lesser density than the sea it is floating on. This force is capable of keeping the objects afloat.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The main reason an object floats or sinks in a liquid substance is because of buoyancy. Buoyant forces are obtained when there are differences in pressure on the opposite sides of an object.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The unit used to describe buoyant force is newton (N).<\/span><\/p>\n<p><span style=\"font-weight: 400;\">It is essential to understand both the concepts of density and relativity to acquire the concept of buoyancy fully.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Density can be defined as the mass per unit volume of material. The density usage is enormous as it could measure how tightly or loosely packed the matter or the substance is.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Density \u03c1 = <\/span><span style=\"font-weight: 400;\">Mass<\/span><span style=\"font-weight: 400;\">Volume<\/span><span style=\"font-weight: 400;\"> = <\/span><span style=\"font-weight: 400;\">M<\/span><span style=\"font-weight: 400;\">V<\/span><\/p>\n<p><span style=\"font-weight: 400;\">kg is the unit for density meanwhile g is the C.G.S unit of density.<\/span><\/p>\n<h3>Relative density<\/h3>\n<p><span style=\"font-weight: 400;\">In Class 9 Physics, the relative density is determined as the ratio of the substance&#8217;s density to the water&#8217;s density. The relative density of a substance is sometimes referred to as the specific gravity.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Below-given is the expression for relative density:<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Relative density = <\/span><span style=\"font-weight: 400;\">Density of a substance density<\/span><span style=\"font-weight: 400;\">\u00a0of water<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Since the relative density is derived using the ratio of similar quantities, there will be a unit to measure it.<\/span><\/p>\n<h3>Example of buoyant force<\/h3>\n<p><span style=\"font-weight: 400;\">Let us look at an example to make it easier for Physics students to understand this concept. Consider a body being thrown in water. Due to the body&#8217;s weight, some amount of water is displaced. This displacement is completely dependent on the object&#8217;s weight or the body. Furthermore, the amount of water displacement is determined by the density of the thrown object. It also depends on the volume.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Now, the centre of buoyancy is the point on the object where the force is applied.\u00a0<\/span><\/p>\n<h3>Why does a body sink or float in water?<\/h3>\n<p><span style=\"font-weight: 400;\">To demonstrate it, we should first know that the water pressure at the bottom is much higher than at the top. If we go down the liquid, we can see that the number of overlying liquid layers that lay one over the other increases. So, in case someone considers a single liquid column, then it is viewed as a mixture of many overlying layers.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In addition, there will be a made-up force applied in an upward direction due to the difference in the pressure. This upthrust could lead to the object&#8217;s acceleration submerged in the upward direction. In general, this force always stays in the vertical direction, which is why it is called force or upthrust upward.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Apart from that, the magnitude of the force acting upwards can be seen as equivalent to the difference in the pressure of the last and top layers. It can also be seen as equivalent to the weight of the fluid displaced.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Therefore, as a consequence of that, floating occurs. The floating of an object is fully dependent on its depth or volume. For instance, an object would float higher on the top layer of the water surface if its density and weight are lesser. On the other hand, if the density and weight of an object are more, it will begin to sink.<\/span><\/p>\n<h3>Applications of buoyancy<\/h3>\n<p><span style=\"font-weight: 400;\">There are so many uses due to the presence of the buoyancy concept. The Class 9 students should know the most common applications. They include swimming, ships, fish, icebergs, submarines, etc. Let us have a detailed understanding of some of the below-mentioned applications:<\/span><\/p>\n<p><strong>1. Hot<\/strong><b> air balloon<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Our earth&#8217;s atmosphere is filled with air capable of exerting buoyant force on any object. Hot air balloons could rise and float due to the containment of buoyant force. Moreover, it will begin to descend when it loses air in the balloon. It could increase the weight of the balloon. Therefore, when the weight of the balloon becomes higher than that of the weight of the atmosphere, it will begin to go down. Furthermore, when the weight of the balloon equals the atmosphere&#8217;s weight, it will stay at a stationary position.<\/span><\/p>\n<p><b>2. Submarine<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Submarines are specifically designed to be used underwater. The large ballast tank present in the submarine can be of great use, which could help control its depth and position. The ballast tank would allow the water to get inside the submarine as it submerges in water. It will also make it weigh more than that of the buoyant force. So, that is how a submarine works using the buoyancy concept.<\/span><\/p>\n<p><b>3. Ship<\/b><\/p>\n<p><span style=\"font-weight: 400;\">The volume of sea or ocean water displaced by the ship is essential in helping it float on the water&#8217;s surface. The volume of the displaced water is approximately equal to the ship&#8217;s weight. The ship is manufactured in a way that it is in hollow shape and lightweight compared to the seawater. The overall density of the ship has to be lesser than the overall density of the water it floats in. Therefore, it is why the buoyant force acting on the ship is larger enough to support its weight.<\/span><\/p>\n<p><b>4. Fish<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Most fishes utilise the principle of Archimedes for swimming in water. The fish can go up and down inside the water body. It could easily fill the swim bladder or the air sac with the help of gases. When the gases come out of their body, it will make the fish light in weight, which will help them float and go up. Fishes use gills, and fins to make this process happen.<\/span><\/p>\n<h3>Example problem<\/h3>\n<p><span style=\"font-weight: 400;\">Let us have a look at this example problem in CBSE Class 9 Physics, to understand the buoyancy concept in a much deeper manner:<\/span><\/p>\n<p><i><span style=\"font-weight: 400;\">Problem: <\/span><\/i><span style=\"font-weight: 400;\">A cubical shaped large iceberg whose specific gravity is 0.9 is floating in the seawater. If the iceberg proportion above the sea level is 20 cm and the specific gravity of the seawater is 1.025, determine the volume of the iceberg.<\/span><\/p>\n<p><i><span style=\"font-weight: 400;\">To find:<\/span><\/i><\/p>\n<p><span style=\"font-weight: 400;\">The total volume of the iceberg<\/span><\/p>\n<p><i><span style=\"font-weight: 400;\">Solution:<\/span><\/i><\/p>\n<p><span style=\"font-weight: 400;\">Let us consider the cubical iceberg side as h,<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Volume of the submerged portion <\/span><span style=\"font-weight: 400;\">= <\/span><span style=\"font-weight: 400;\">h &#8211; 20<\/span><span style=\"font-weight: 400;\"> x<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The weight of the iceberg during floatation = weight of the displaced water<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The side of the iceberg = 164 cm<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Hence, the volume of the iceberg = 4.41<\/span><\/p>\n<p><i><span style=\"font-weight: 400;\">Answer: <\/span><\/i><span style=\"font-weight: 400;\">4.41<\/span><\/p>\n<h3>Conclusion<\/h3>\n<p><span style=\"font-weight: 400;\">To conclude, the CBSE Physics students have obtained all the information related to buoyancy. In this article, they have learnt about buoyant force in detail while looking at its example. The students are also taught about relative density. Moreover, we have seen a detailed explanation of how and why objects float or sink when it is inside the water body.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In addition to that, the students acquired knowledge on the applications of buoyancy and how it is being used in different objects. Finally, an example problem is given for the CBSE students to understand the whole concept thoroughly to be beneficial in their Physics board exam.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>How do objects float in a fluid? The answer to this question is &#8216;buoyancy&#8217;. A buoyant force is a type of force that occurs in all gases and fluids. This force acts in an upward direction due to the presence of gravity. It is exerted opposite to the gravitational force. The buoyant force is found [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":231794,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3581],"tags":[2564,3162],"class_list":["post-153088","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cbse","tag-cbse-class-9","tag-cbse-class-9-physics"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.0 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>What is buoyancy? 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