Railway Science (Physics-Force and Pressure)

Tendency of an object to continue its state of rest or of uniform motion until or unless an external force is applied to it. Inertia is directly proportional to mass of an object. Formula : I =  𝐿/ω (where I is inertia, L is angular momentum, ω is angular velocity).

Lubricants form a thin layer between surfaces to reduce friction between them. Example - Engine oil, Grease. Rough surface increases Friction. Friction - force that opposes motion between any two surfaces which are in contact. Type of friction - rolling, sliding, static, fluid.

Drag forces :- It always acts in the opposite direction to fluid flow. Example - Drag on a ship moving in the water. Buoyancy (Upthrust) :- An upward force exerted by any fluid to oppose the weight of an immersed object. Convection:- Transfer of heat due to bulk movement of molecules in fluids such as liquid or gas. Frictional force - Force created when two surfaces come into contact as well as slide against themselves.

It is generated by two surfaces that contact and slide against each other. Example - Rubbing hands, climbing a rock. Force of Gravity (Gravitational force) - A force that attracts all physical forms having mass. Example - Earth’s gravitational force. Magnetic Force - Force on an object due to interactions with a magnetic field. Example - compass, electric motor. Electrostatic Force (Coulomb Force) - The attraction or repulsion of objects due to their electric charge. Example - Rubbing the rod with silk clothes, balloons rubbed with hair.

Frictional force exerted by fluids (air and water) on objects moving through them is known as "drag". Electrostatic Force - Attraction or repulsion between two charged particles due to their electric charges. Magnetic Force - Attraction or repulsion that arises between electrically charged particles due to their motion. Force of Gravity - also known as Gravitational Force it pulls objects with mass towards each other.

This action is called ‘Polishing The Ball’. Cricketers shine the ball because this increases the chances that the bowler will get the ball to swing in the air. Friction - Force that resists the sliding or rolling of one solid object over another. Other Example of Friction - Driving of a vehicle on a surface, Applying brakes to stop a moving vehicle, Skating.

Frictional force: It is the force generated by two surfaces that contact and slide against each other.It depends on the nature of surfaces in contact. Gravitational force: The mutual attraction between objects with mass. Magnetic force: The force of attraction or repulsion between electrically charged particles due to their motion. Muscular force: The force generated by muscles during contraction.

Friction - A contact force that always opposes the relative motion of two objects which are in contact. It acts in the direction opposite to the direction of motion of the object. Static friction - It occurs when the body is in the position of rest. Dynamic friction - It occurs when the body is in the position of motion. The value of static friction is greater than dynamic friction.

Force exerted on a surface per unit area; approximately equal to Earth's average atmospheric pressure at sea level. 1 ATM = 101325 Pascals = 760 mm Hg = 760 torr = 14.7 psi. Temperature: Measure of hotness or coldness of a body; S.I. unit - kelvin, Non SI unit - Fahrenheit, Celsius . Radiation: Energy that comes from a source and travels through space at the speed of light, SI unit - becquerel (Bq). Convection - A process by which heat is transferred by movement of a heated fluid.

Pressure : Formula: Pressure = Force/Area, Unit - Newton /meter² . Torque: a measure of the force that can cause an object to rotate about an axis, Formula - Force × radius × sin𝜃, Unit - Newton-meter. Density : Mass of a unit volume of a material substance, Formula - Mass /Volume, Unit - Kg/meter³ .