| Aim | To determine the correlation between the loss in weight of a solid when it is completely submerged in: 1 tap water 2 highly saline water, the weight of the water displaced by the solid will be measured using two different types of solids. |
| Materials Required | A spring balance, a metal bob, a cotton thread, an overflow can, a glass beaker, tap water, salty water, an iron stand. |
| Theory | Fluids are substances that flow and can be gases or liquids. The buoyant force, which is the upward force that fluids exert on a body, is referred to as buoyancy. Thrust is a force that acts perpendicular to the surface of a body, and its unit of measurement is the Newton. Pressure is the force per unit area, which can be expressed as thrust divided by area. Its unit is Nm-2 or Pascal (Pa). The weight of a body can be determined by multiplying its mass by the acceleration due to gravity. When a body is immersed in a liquid or water, it displaces some of the liquid, and the volume of liquid displaced is equal to the total volume of the solid. The mass of liquid displaced can be calculated using the volume and density of the liquid. The weight of liquid displaced can be found by multiplying the volume, density, and acceleration due to gravity. The loss in weight of a body when immersed in fluid can be determined by subtracting its weight in air from its weight when immersed in the liquid. The amount of upward force, or buoyant force, depends on the density of the liquid. The up thrust is greater in denser liquids. Archimedes’ principle states that when a body is partially or fully immersed in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by the body. |
| Procedure | A. Procedure for determining the zero error and least count of a spring balance: Suspend the spring balance to an iron stand. Study the scale of the spring balance and determine its least count. Record any error in the scale reading as ‘x’ gf. B. Procedure for finding the weight of a solid metal bob in air: Tie a thread to the metal bob and suspend it on the hook of the spring balance. Record the weight of the metal bob in air as ‘Wr’. C. Procedure for finding the weight of the metal bob immersed in tap water and recording the apparent loss in weight: Fill an overflow can with water such that its level touches the spout of the can. Place the overflow can under the spring balance so that the metal bob is fully immersed in the water of the can. Record the weight of a beaker (P1) placed at the mouth of the spout of the overflow can. Record the loss in weight (W2) of the metal bob when it is suspended in water. Collect the water that overflows in a beaker until the last drop that comes out of the spout. Weigh the beaker with water (P2). Calculate the weight of the displaced water (P2-P1). Calculate the loss in weight of the metal bob when it is immersed in water. D. Procedure for finding the weight of the metal bob immersed in salty water and recording the apparent loss in weight: Prepare salty water by dissolving common salt in 300 mL of water in a 500 mL beaker until a saturated solution is obtained. Repeat steps 1-8 of procedure ‘C’ using the same metal bob and the prepared salty water. Tabulate all the observations. |