Railway Science (Physics-Force and Pressure) (Part-III)

Displacement - It is the distance between an object's initial position and its final position. It is usually measured or defined along a straight line. Displacement is a vector quantity which has both magnitude and direction.

It is a vector quantity that describes both the speed and direction of motion of an object. Acceleration is the rate of change of velocity.
Acceleration = 𝐶ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑣𝑒𝑙𝑜𝑐𝑖𝑡y/𝑇𝑖𝑚𝑒 𝑡𝑎𝑘𝑒n. The SI unit of acceleration is meters per second squared (m/s²).

The natural tendency of an object to resist its stationary state or its state of motion. Law of Inertia, also known as First law of motion states that every body continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external force to act otherwise.

It is a vector quantity with both magnitude and direction. The SI unit of weight is Newton (N). Formula : Weight = mass × acceleration due to gravity.

It is an external agent capable of changing a body’s state of rest or motion, SI unit - Newton. Inertia is the property of a body by virtue of which the body opposes the change in its initial state of rest or motion with uniform speed on a straight line. SI unit - kg.m². Momentum is defined as the product of mass and velocity of the body and is the measure of the amount of motion contained in a body. SI unit - kg ms⁻¹ . Velocity (V) is defined as the displacement of the object in a unit time interval. SI unit - m/s.

Force is an external agent capable of changing a body’s state of rest or motion. It is a vector quantity (magnitude and direction). Formula : Force (F) = Mass (m) × Acceleration (a). SI unit (Newton). Other units - Dyne, poundal, pound-force, kip, kilo pond. Potential Energy (PE) = mgh, Where m = mass of the object, g = acceleration due to gravity, h = height of the object. Momentum (p) = mv, Where m = mass and v = velocity. Newton's First equation of motion : v = u + at, where u = Initial velocity, v = Final velocity, a = Acceleration and t = Time of motion.

The opposing force that comes into play when two bodies come in contact with each other. Lubrication and Smoothening of surfaces are done to reduce friction. f = µ N , where, F = friction force, µ = coefficient of friction, N = normal force. Applications of Friction - Friction finds application when matchsticks are ignited. It is possible to write on books as there is friction between pen and paper. We can walk on the ground because of the force of friction.

The SI unit of weight can be measured in kg⋅m/𝑠² (kilograms 2 times metres per second square) which is equal to a newton (N). Weight of any substance (W) = mg. Where m = mass, g = gravity. Weight has both the magnitude and direction. Hence, weight is a vector quantity. Other important SI Units : Mass - Kilogram (Kg). Length - meter (m). Time - Seconds (s). Current - Ampere (A). Temperature - Kelvin (K). Amount of substance - mole (mol). Luminous Intensity - Candela (cad).

Force is equal to the rate of change of momentum; It is the product of mass and acceleration (F = ma). Newton's first law of motion - Law of Inertia (An object will continue to be either in a state of motion or in a state of rest unless an external force acts on it). Newton's third law of motion - For every action (force), there is an equal and opposite reaction. Newton's Law of Universal Gravitation - All objects attract each other with a force that is directly proportional to the product of their masses and inversely proportional to their distance of separation.

Force (defined as a product of mass and acceleration). Newton’s First law: A body continues to be in its state of rest or of uniform motion along a straight line unless it is acted upon by some external force to change the state. Mass defines the amount of matter present in the body. The property of the body to resist change is called Inertia. Momentum is defined as the product of mass and velocity (p = mv).