D1 Gravitational Fields

Kepler 1

the orbit of each planet is an ellipse with the sun at one focus

Kepler 2

the line joining the sun and planet sweeps equal areas in equal times

Kepler 3

the relationship between the orbital period of planet (T) and orbital radius (R)

gravitational field strength

the force per unit mass acting on a negligibly small “test mass” placed at that point

weightlessness

an object in free fall in which the only force acting on it is gravity

gravitational potential

work done per unit mass to move a small test mass from infinity to the point

equipotential lines

lines drawn onto a gravitational field joining together points in space which have the same gravitational potential

uniform field

equipotential lines drawn in right angles to gravitational field lines

radial field

potential gradient

the relationship between gravitational field strength (g) and gravitational potential (V)

escape speed

speed at which an object would have to be thrown from a planet’s surface to “escape” the gravitational influence of the planet