Railway Science (Physics-Heat and Thermodynamics)

Designing of airplane wings. Archimedes' Principle - It states that an object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces. Applications - Used in designing ships and submarines, Used in lactometers to determine the purity of milk, Used in hydrometers to determine density of fluids.

Viscosity: Measure of a fluid’s resistance to flow. SI unit of viscosity is N-s/m² or pascal-second (Pa - s). Example - Honey, Molasses, Melted chocolate. Rigidity - The inability of a solid to change its shape. Example - Table, chair, fan.

Due to the difference in their densities. Cork has a lower density than water and iron nail has more density than water. Density - The amount of matter present per unit volume, measured in Kg m-³ . Density = Mass / Volume. A substance having lower density than a liquid will float on it and a substance having higher density than a liquid will sink in it.

Archimedes principle. Hydrometer (used to determine the density of liquids). It is also based on the Archimedes principle. The hydrometer basically consists of a weighted, sealed, long-necked glass bulb immersed in the measured liquid; the flotation depth shows the liquid density, and the neck can be calibrated to read the actual gravity value. Principle of periscope - It is based on the Laws of Reflection which states that the light from the object falls on a mirror. Principle of potentiometer - The potential difference between any two points of the potentiometer wire is directly proportional to the length of wire.

Magnitude. Buoyancy (buoyant force) is an upward force exerted by a fluid on an immersed object in a gravity field. It works on Archimedes' principle. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bottom of a column of fluid is greater than at the top of the column. Applications: Boat sailing on the river, Iceberg floating on water, Helium balloon rising in the air.

Density: It is the mass of a body per unit volume. Example - dense material like Iron takes more mass in a given volume than of wood.
Formula: 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 (ρ) = 𝑚𝑎𝑠𝑠 (𝑚)/𝑉𝑜𝑙𝑢𝑚𝑒 (𝑉)
SI Unit is kg/m³
. Sinking: The object will sink, if the density of the object is more than the density of the liquid it is placed in.

Upthrust (Buoyancy) : It is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. Example : A boat or a ship floating in the water and the floating of cork in water. When an object is floating on a water surface then the apparent weight of the floating object is Zero. Mechanical force - The force generated by the means of a machine. Frictional force - A force that resists relative motion between two surfaces in contact.

The object floats. Whenever an object is immersed in a liquid, either partially or fully, an upward force is exerted on the object by the liquid. This upward force is called upthrust or buoyant force. Example - Feather in water. If the density of an object immersed in a liquid is higher than that of the liquid, the object will sink. Example - Rock in water.

Archimedes' principle states that the buoyant force exerted on a body submerged in a liquid is equal to the weight of the liquid displaced. Archimedes’ Principle Formula : Fᵦ = ρ × g V, where Fᵦ × is the buoyant force, ρ is the density of the fluid, V is the submerged volume, and g is the acceleration due to gravity. Applications : Submarine, Hot-air balloon, Hydrometer

Density is mass per unit volume. ρ = m/v . Density is the amount of space which a substance or an object occupies. The SI unit of density is kg/m³. Relative density is a comparative measure of the density of a substance to the density of a reference substance. It has no unit.