Railway Science (Physics-Force and Pressure)

Lubricants - A substance used to facilitate relative motion of solid bodies by minimizing friction and wear between interacting surfaces. Main functions - Avoid machine wear, Corrosion protection, Cooling by dissipating heat from the surface, Cleaning by transporting dirt particles to the filter.

The reading on the scale is the magnitude of the force. Springs are components which deflect under load to store relatively large amounts of energy. Spring balance works on the principle of Hooke's law. Hooke’s law formula: F = - K x (Where, F - amount of force, x - displacement in the spring, k - spring constant or force constant). Types of Spring: Helical spring, Leaf spring, Torsion spring, Disc spring, Conical volute spring, Special purpose spring.

Viscosity - A measure of a fluid's thickness and its resistance to flow. High viscosity fluids flow slowly, while low viscosity fluids flow more easily. Other units of Viscosity - Newton-second per square metre (Ns/m²) or pascal-second (Pa.s). Dimensional formula - [ML⁻¹T ¹].

Static friction is a force that keeps an object at rest (Examples: Papers on the tabletop, a car parking on a hill, A towel hanging on a rack). Rolling friction: The resistive force that acts on the motion of a rolling object (Examples: Ball bearings). Sliding friction: The resistive force that acts on two objects sliding against each other (Examples: Coaster sliding against a table, rubbing both the hands together to generate heat).

A force or a push (mostly reactive). When a system pushes or accelerates mass in one direction, there is a thrust (force) just as large in the opposite direction. Formula : T = v 𝑑𝑚/𝑑t where T is thrust, v is velocity, dm is 𝑑𝑚 𝑑𝑡 change in mass and dt is change in time. S.I unit - Newton (N). Spring Force - Restoring force exerted by a spring when it is stretched or compressed. Mechanical Force - Force that involves direct interaction between objects which result in the change of object’s motion. Example - Someone pushing a door. Magnetic Force - Attraction and repulsion between electrically charged particles due to their motion. Example - Compass.

Other technique to reduce friction: Lubricants - Form a thin layer between surfaces so they do not directly rub each other. Example - Engine oil. Rough surface increases Friction. Friction - Force that opposes motion between any two surfaces which are in contact. Type of friction - Rolling, sliding, static, fluid.

A device that consists of a ring of small metal balls. The axle is fixed on the inner side of a ball bearing and the wheel is fixed to the outer side of the ball bearing. Other methods of reducing friction - Lubricating the surfaces (Oil and grease).

A nail has a pointed end so that the surface area is less, when the surface area is less the pressure increases which makes it easy for the nail to be driven into the wall or wherever it may be inserted. Pressure (P) is defined as the physical force exerted on an object. The force applied is perpendicular to the surface of objects per unit area. The basic formula for pressure is F/A (Force per unit area). Unit of pressure is Pascal (Pa).

A spring balance is a simple device that is used to measure weight or force. It consists of a coiled spring that is attached to a pointer and a calibrated scale. When a force is applied to the spring, it stretches, and the pointer moves along the scale, indicating the magnitude of the force. Types of springs : Compression, Extension, spiral, Torsion. Nylon is a strong , flexible artificial fiber.

The maximum force exerted by a surface on a body so long as it remains stationary is called the force of Static friction. Examples - Pushing heavy objects, load on a conveyor belt, plants root fixed on the ground. Sliding friction - The resistance created by any two objects when sliding against each other. Example - Coaster sliding against a table, Sliding on a wet floor.