OCR Physics Year 2 - Gravitational Fields Vocabulary

A set of vocabulary flashcards covering key definitions, equations, and principles from Topic 5.4 (Gravitational Fields) of the OCR Physics Year 2 textbook.

Gravitational field

The region around a body in which other bodies will feel a force due to the mass of the body.

Gravitational field lines

Lines that show the shape of a gravitational field, where the direction of the line at any point is the direction in which a small mass would move when placed at that point.

Gravitational field strength

The force acting per unit mass at a point in a gravitational field, defined as $g = \frac{F}{m}$ with units of $N\,kg^{-1}$.

Lagrange points

Points between bodies where their gravitational fields exactly cancel and the net gravitational force on an object is zero.

Newton's law of gravitation

States that the gravitational force of attraction between two point masses is directly proportional to the product of their masses and inversely proportional to the square of their separation: $F = -\frac{GMm}{r^2}$.

Universal gravitational constant

The constant $G$ in Newton's law of gravitation, having a constant value of $6.67 \times 10^{-11}\,N\,m^2\,kg^{-2}$ throughout the universe.

Kepler's third law

States that the square of the orbital period of a planet orbiting the Sun is proportional to the mean radius of its orbit cubed ($T^2 \propto r^3$).

Geostationary orbit

An orbit of the Earth made by a satellite that has the same time period (24 hours) and orbital direction as the rotation of the Earth and lies in the equatorial plane.

Gravitational potential

The work done in moving unit mass from infinity (where gravitational potential is defined as zero) to a specific point in a gravitational field, measured in $J\,kg^{-1}$.

Gravitational potential energy

The work required to move a body of mass $m$ from infinity to a point in a gravitational field, calculated as $E = mV_g = -\frac{GMm}{r}$ and measured in joules ($J$).

Escape velocity

The minimum launch velocity required to move an object from a point in a gravitational field to infinity, calculated using $v = \left(\frac{2GM}{r}\right)^{1/2}$.