Gravitation and Related Concepts - Vocabulary Flashcards

A set of vocabulary flashcards covering key terms and definitions from gravitation, weight, mass, buoyancy, pressure, and related concepts as presented in the lecture notes.

Universal Law of Gravitation

Every object in the universe attracts every other object with a force proportional to the product of their masses and inversely proportional to the square of the distance between their centers; the force acts along the line joining the centers.

Gravitational Constant (G)

Proportionality constant in F = G m1 m2 / r^2; value = 6.67×10^-11 N·m^2/kg^2.

Mass

Amount of matter in a body; a scalar quantity; constant everywhere; measured in kilograms (kg).

Weight

The force with which a planet (e.g., Earth) attracts a body; a vector quantity measured in newtons (N); given by W = m g and depends on g.

Acceleration due to gravity (g)

Rate of change of velocity due to gravity near Earth’s surface; approximately 9.8 m/s^2 (varies with height, depth, and location).

Free fall

Motion of a body under gravity with no other forces acting (neglecting air resistance); acceleration is g toward Earth.

Centripetal Force

Inward force that keeps an object moving in a circle; always points toward the center; can be provided by gravity or another force.

Archimedes’ Principle

The upthrust on a partially or fully immersed body equals the weight of the fluid displaced by the body.

Upthrust (Buoyancy)

Upward force exerted by a fluid on an immersed object; causes floating or sinking depending on balance with weight.

Buoyancy

Same as upthrust; the upward force that enables objects to float in fluids.

Density

Mass per unit volume (ρ = m/V); SI unit kg/m^3; determines whether an object floats or sinks in a given fluid.

Pressure

Force per unit area (P = F/A); SI unit is the pascal (Pa, N/m^2); in fluids, pressure increases with depth and acts in all directions.

Thrust

Force acting perpendicular to a surface; SI unit Newton (N); e.g., weight of a book on a table applies thrust on the table.

Newton’s Third Law

For every action, there is an equal and opposite reaction; the forces between two interacting bodies are equal in magnitude and opposite in direction.

Variation of g (gravity) on Earth

g decreases with height above Earth’s surface and with depth; is maximum at the poles and minimum at the equator due to shape and rotation.

Weight vs Mass distinction

Mass is the amount of matter (invariant); weight is the gravitational force acting on that mass (depends on g).

Gravitational force between two bodies

F = G m1 m2 / r^2; attractive force between two masses separated by distance r.

Mass on Moon vs Earth (relative weight)

For the same mass, weight on the Moon is about 1/6 of weight on Earth due to smaller g on the Moon.

Surface gravity value around Earth

Near Earth’s surface, g ≈ 9.8 m/s^2; sometimes rounded to 10 m/s^2 for ease.

Equilibrium: floating condition

An object floats if the upthrust equals its weight; sinks if its weight exceeds upthrust; remains suspended if densities are equal.

Pressure in liquids vs depth

Hydrostatic pressure increases with depth; liquids exert pressure on bases and walls; density of liquid affects pressure magnitude.

Free-fall in air vs vacuum

In vacuum (no air resistance), all objects fall with the same acceleration g regardless of mass; air resistance alters this in real conditions.