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

Rolling Friction - This type of friction occurs when an object rolls over a surface. It is generally lower than dynamic friction. Limiting Friction - It is the maximum amount of friction that can exist between two surfaces before one of them starts sliding or moving. Static Friction - It is the frictional force between two surfaces that are in contact but not moving relative to each other.

Newton's Third Law: Every action has an equal and opposite reaction. In rockets, engine action produces hot exhaust gasses, creating thrust. This generates a reactionary force in the opposite direction. Newton's First Law (law of inertia): An object will remain at rest or in uniform motion unless acted upon by an external force. Newton's 2nd law: The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force acts.

An unbalanced force causes acceleration according to Newton's second law of motion (F (force) = m (mass) × a (acceleration). This acceleration results in a continuous change in the speed of the body. As long as the unbalanced force is applied, the body's speed will continue to change, either increasing or decreasing depending on the direction of the force relative to the body's initial velocity.

(Newton First law of Motion) - It states that ‘An object will continue to be in the state of rest or in a state of motion unless an external force acts on it’. Examples - The tendency of moving back when the stationary bus starts to move, Jerk experienced when the lift operates suddenly, Moving forward when a sudden break is applied, Athlete taking a short run before a jump.

When a force acts on an object and causes it to move in the same direction as the force, the work done by that force is considered positive. When the displacement is perpendicular to the force, the work done by the force is zero. If there is no displacement, no work is done by the force.

The direction of acceleration is determined by the general principle that if an object is slowing down, the acceleration is in the opposite direction of the motion. Hence, with negative acceleration, the velocity of a body decreases.

Momentum (kgm/s) - The product of the mass of a particle and its velocity. It is a vector quantity. Force (Newton) - Force is an external agent capable of changing a body's state of rest or motion. Velocity (m/s) - The Displacement of an object in a unit time interval.

It is the mutual interaction between the two bodies. Momentum (kgm/s)- It is defined as the product of mass and velocity of the body. Velocity (m/s) - The displacement of the object in a unit time interval is called velocity. Pressure (Pascal) - It is the force applied per unit area in a direction perpendicular to the surface of the object.

Friction always acts in the opposite direction to movement, i.e. it opposes the motion of any object. For example, air resistance is a frictional force which opposes motion through the air. Friction is caused by the irregularities on the two surfaces in contact.

An interaction of one object on another that causes the second object to accelerate or change velocity or direction. Momentum takes place in the direction of the applied force (according to the Second law of motion). Momentum (p) is a product of mass and velocity. It is a vector quantity. Its direction is the same as that of the velocity. p = mv. Unit of momentum is kgm/s.