⚝I HOPE IT WILL HELPS YOU ↡Explanation:Skip to main contentSkip to primary sidebarSkip to footerMENUCBSE TutsCBSE Maths notes, CBSE physics notes, CBSE chemistry notesNCERT Class 9 Science Lab Manual – Pressure NCERT Class 9 Science Lab Manual – PressureEXPERIMENTAimTo observe and compare the pressure exerted by a solid iron cuboid on fine sand/ wheat flour while resting on its three DIFFERENT faces and to calculate the pressure exerted in the three different cases. TheoryThrust: The net force exerted by a body in a particular direction. (Thrust = weight of body)This force is perpendicular to the surface. When you stand on LOOSE sand or lie down on the sand, the thrust acting on the surface is same, but the effects are different. Pressure increases with decrease in the area of contact. S.I. UNIT of Thrust is newton (N).Pressure: The thrust acting on unit area is called pressure.S.I. unit of pressure = (N m-2) or pascal (Pa)1 Pa = 1 N/l m2Cuboid and its surface areaCuboid: It is a rectangular parallelepiped whose faces are not equal in length. A solid cuboid has six faces. A pair of opposite faces are equal and have same surface area.In the given cuboid (figure)NCERT Class 9 Science Lab Manual - Pressure 1Area of face ABCDi. e. Surface Area = length x breadth = 15 cm x 10 cm =150 cm2Area of face BCGFSurface Area A2= length x breadth = 10 cm * 5 cm = 50 cm2Area of face ABFESurface Area A3 = length x breadth = 15 cm x 5 cm = 75 cm2Materials RequiredA solid cuboid made of iron with dimensions 5 cm x 10 cm x 15 cm, a tray with fine sand/beach sand (Tray: 10 x 20 x 30 cm), spring balance, sting and clamp stand.A. Determination of weight of the given cuboidProcedureTie the string to the cuboid.Note the zero error of the spring balance.Suspend the cuboid on the hook of the spring balance that is hung on the clamp stand. Note the reading of the spring balance. If the spring balance shows the reading in newtons, record the reading shown as the weight of the cuboid.If the spring balance shows the reading in g, then convert the reading into newtons, as follows:Convert the ‘g’ into kg. Multiply it with (g = 9.8 m/s2)ObservationsNumber of DIVISIONS on spring balance between 0 to first (W0) reading………………. (n)Least reading of the spring balance = \frac { { W }_{ 0 } }{ n } =……….Reading of spring balance suspended freely in air (zero error) = ‘0’Weight of the Cuboid =………….. N.B. Determination of the pressure exerted by different faces of cuboidProcedureOn a plain table keep a tray as shown in the figure.Fill in the tray with fine sand.Place the solid cuboid on the tray with fine sand as follows:Case (a) Face 5 cm x 10 cm should be in contact with the sand.Case (b) Face 10 cm x 15 cm should be in contact with the sand.Case (c) Face 5 cm x 15 cm should be in contact with the sand.Carefully observe the depressions made by all the three cases and record the maximum and the minimum depression caused by the cuboid using a scale.Do the calculations to find the pressure exerted by each dimension i.e. case a, b and c.Observation and calculationsThe maximum depression in the sand is seen in case (a) .The minimum depression in the sand is seen in case (b) .1. The weight of the cuboid = 1 kg2. Thrust exerted by the cuboid = (Force) = m x ae.g. = 1 x 9.8 m/s2 = 9.8 NThrust exerted by any surface of the cuboid remains the same = 9.8 N.3. Surface areaCase (a) 5 cm x 10 cm = 50 cm2 = 5 x10-3 m2Case (b) 10 cm x 15 cm = 150 cm2 = 15 x10-3 m2Case (c) 5 cm x 15 cm = 75 cm2 = 75 x10-4 m2NCERT Class 9 Science Lab Manual - Pressure 2Observation TableMass of the cuboid (m) = 1000 g = 1 kg.NCERT Class 9 Science Lab Manual - Pressure 3ConclusionFor any given cuboidSmaller the surface area of contact, greater is the pressure exerted.The pressure exerted by the body depends on the surface area that comes in contact with the sand.The depression on the sand is directly proportional to the pressure exerted by the body.PrecautionsCarefully and gently place the cuboid on the sand.The spring balance should be checked for proper range and zero error.Weight of the cuboid and measuring of the height of depression on sand should be taken accurately.Sand should be wet.VIVA VOCEQuestion 1:Define thrust.Answer:The force acting on a body perpendicular to its surface is called thrust.Question 2:Give the S.I. unit of thrust.Answer:NewtonQuestion 3:Define pressure.Answer:Thrust exerted per unit area is called pressure.Question 4:State the S.I. unit of pressure.Answer:Pascal (Pa).Question 5:What is one pascal?Ans.When a force of 1 N acts on a surface area of 1 m2 then the pressure is said to be one pascal.Question 6:What is the blood pressure of a normal human being?Answer:It is 120/80 mm of mercury. The blood flows in the vessels by a pressure that it can withstand.PRACTICAL BASED QUESTIONSQuestion 1:A body with dimensions 1 cm x 2 cm x 3 cm is placed on sand with three different surfaces. 贏 丟☄▶plz mark me as brain list ▶THANKS