Railway Science (Physics-Gravitation)

Acceleration due to gravity is the acceleration gained by an object due to gravitational force. It’s a vector quantity (both magnitude and direction). Its SI unit is m/s². The Formula of Acceleration Due to Gravity : g = GM / r² where, M = Mass of Earth, r = Radius of the Earth, and G is a universal gravitational constant. The value of acceleration due to gravity on the moon is one-sixth of its value on the earth. It is equal to 1.625 m/s² .

Formula: weight (w) = mass (m) × acceleration due to gravity (g). Mass is uniform regardless of its location, whereas weight of a body does change as per its location. Example: Weight of a person on earth is 6 times as compared to the weight on the moon.

Force is a push or pull upon an object resulting from the object's interaction with another object. Gravitational force - An attractive force that exists between all objects with mass.

Weight of the body  changes from place to place because it depends on the gravitational acceleration. W (weight) = m (Mass) × g (gravitational acceleration). The gravitational acceleration is 1/6 on the surface of the moon (1.625 m/s²) as compared to Earth (9.8m/s²). Hence, the weight on the moon is 1/6 th of Earth.

This is because the Earth is not a perfect sphere; it is slightly flattened at the poles and bulges at the equator due to its rotation. This flattening causes the gravitational force to be slightly stronger at the poles compared to the equator. As a result, objects weigh slightly more at the poles than at the equator.

Centre of mass - It is the average position of all the parts of the system, weighted according to their masses. Centre of pressure - refers to the point where the resultant force due to fluid pressure acts on a submerged or partially submerged object.

A force that makes a body follow a curved path. Any object moving in a circle (or along a circular path) experiences a centripetal force. Gravitational force - The force of attraction experienced by two or more objects in contact. Centrifugal force - The apparent outward force on a mass when it is rotated. Tension - A type of force experienced when a rope, wire, or string is pulled by forces acting from opposite sides.

Gravitational force: A force of attraction (attractive force) that attracts all physical forms having mass. Gravity is the force by which an earth draws objects toward its center. The acceleration due to gravity on Earth or the value of g on Earth is 9.8 m/s².

Freefall refers to a situation in physics where the only force acting on an object is gravity. Weightlessness is a term used to describe the sensation of a complete or near-complete absence of weight. Astronauts orbiting the Earth often experience the sensation of weightlessness.

Gravitational constant (G) is a constant representing gravity strength between objects. Distance from Earth's center (r) influences gravity; farther from the center means weaker force and smaller acceleration. The acceleration due to gravity at a height of h above the earth's surface, g(h) = g (1- 2h Rₑ) and variation of acceleration due to gravity with depth g(d) = g(1 - d/Rₑ) where, Rₑ - earth’s radius, h - height, d - depth.