Gravitational fields GapFill

Gravitational fields are regions in which masses experience a force. Gravitational forces between masses  only affect certain massesare always repulsiveare always attractiveare time-dependent. The strength of this force is given by Newton's law of gravitation, which can be written as  F = Gm₁m₂/r²F = Gm/rF = Gm/r²F = Gm₁m₂/(4πr²).
In general, gravitational field strength is defined as  the force experienced by a bodythe force experienced per unit mass of a bodythe gravitational charge per unit mass of a bodythe energy 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 = GM/r²g = Gm₁m₂/(4πr²)g = Gm₁m₂/r²g = GM/r.
Gravitational potential is the  force feltmassgravitational potential energy per unit massmass per gravitational energy for a given body at a specific point in a gravitational field, and has a value of zero at  various pointsno pointsinfinitythe centre of a body. A surface where this is constant is called  a zero surfacean equiforcean equipotentialuniform, 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  T ∝ rT² ∝ r³T³ ∝ 1/r²T ∝ r³. The total energy of a satellite is equal to the satellite's  gravitational potential energy × kinetic energygravitational potential energy + kinetic energykinetic energy - gravitational potential energykinetic energy. For an object to leave orbit, it must achieve escape velocity, which is equal to  2GM/r√(2GM/r)√(GM/r²)GM/r².