Gravitational Fields Definitions

Kepler’s 1st Law

The orbit of a planet is an ellipse with the sun at one of the two foci

Kepler’s 2nd Law

A line segment joining a planet to the sun sweeps out equal areas in equal times

Kepler’s 3rd Law

The square of the orbital period is directly proportional to the cube of its axis

Gravitational Force (F)

An attractive force between two masses, outlined by Newton’s law of gravitation

Gravitational Field Strength (g)

The gravitational force per unit test mass

Gravitational Potential Energy (E)

The work done to move a test mass from infinity to a position in a gravitational field

Gravitational Potential (V)

The work done per unit test mass to move a test mass from infinity to a position in a gravitational field

Newton’s Law of Gravitation

The force is directly proportional to the product of the masses and inversely proportional to the square of the radius

Unit for Gravitational Force

N

Unit for Gravitational Field Strength

N/kg or ms-2

Unit for Gravitational Potential Energy

J

Unit for Gravitational Potential

J/kg

For the F against r graph, what does it show

That F is inversely proportional to r squared (Newtons Law of Gravitation)

For the F vs r graph, what does the area under the curve represent

The work done moving an object between those distances, which equals the change in gravitational potential energy

Geosynchronous Satellite

Takes 24 hours for 1 orbit

Geostationary Satellite

Stays above the same point on Earth, T=24hrs, above the equator

Polar Satellite

Rotates around the poles, used for imaging the whole planet

Equation for the change in energy of a satellite

change in E= -GMm/2r (1/r after - 1/r before)