Gravitational fields

What is a gravitational field

A force field around every mass that attracts other masses

What direction do arrows point in a gravitational field

Where a mass would accelerate in the field

What is a uniform field and a radial field

Radial field: Straight lines all coming from 1 point, leading to an inverse square relationship in field strength

Uniform field: All field lines are parallel and equidistant 

What is gravitational potential energy

The energy of an object due to its position in a gravitational field

Why is GPE/potential always negative

Gravity is always attractive, so work done is needed to reach infinity, to escape the field

How is potential defined at a point

The work done per unit mass to move an object from infinity to said point

What is an equipotential surface

A surface in a field where every point has the same potential, so moving along this surface requires zero work done

What is keplars third law

r³/T² is constant for all objects in an orbit

What is escape velocity

The minimum velocity required for an object to leave the gravitational field of a body

What is a geosynchronous orbit

An orbit which has the same time period as a day

Energy of a satellite in a circular orbit