Gravitational fields GapFill

Gravitational fields are regions in which masses experience a force. Gravitational forces between masses  only affect certain massesare always attractiveare time-dependentare always repulsive. The strength of this force is given by Newton's law of gravitation, which can be written as  F = Gm₁m₂/(4πr²)F = Gm/rF = Gm/r²F = Gm₁m₂/r².
In general, gravitational field strength is defined as  the energy per unit mass of a bodythe gravitational charge per unit mass of a bodythe force experienced by a bodythe force experienced per unit mass of a body in a gravitational field. The equation for the gravitational field strength of a radial field is given by  g = Gm₁m₂/r²g = Gm₁m₂/(4πr²)g = GM/rg = GM/r².
Gravitational potential is the  massmass per gravitational energyforce feltgravitational potential energy per unit mass for a given body at a specific point in a gravitational field, and has a value of zero at  no pointsthe centre of a bodyinfinityvarious points. A surface where this is constant is called  uniforman equiforcean equipotentiala zero surface, and no work is done when an object moves along this surface.
Gravity controls how bodies orbit each other. Orbital period and radius are related by  T² ∝ r³T ∝ r³T³ ∝ 1/r²T ∝ r. The total energy of a satellite is equal to the satellite's  gravitational potential energy × kinetic energykinetic energygravitational potential energy + kinetic energykinetic energy - gravitational potential energy. For an object to leave orbit, it must achieve escape velocity, which is equal to  √(GM/r²)√(2GM/r)GM/r²2GM/r.