Gravitational Fields Flashcards
A gravitational field
The region around a body in which other bodies will feel a force due to the mass of the body
Gravitational field lines
Show the shape of the field and the direction of the field line at a point is the direction in which a small mass would move when placed at that point
Gravitational field strength
The force acting per unit mass
g = F/m, g = -GM/r^2
Newton’s law of gravitation
F = - (GMm/r^2)
Keplars first and second laws
- planets travel around the sun in elliptical orbits
* a line joining the sun to a planet will sweep out equal areas in equal times
Keplars third law
The time period of the orbit square is proportional to the mean radius cubed.
T^2 = (4π^2/GM)r^3
Geostationary orbit
An orbit of the Earth made by a satellite that has the same time period and orbital direction of the Earth (24 hours)
Gravitational potential at a point in a gravitational field
The work done in moving unit mass from infinity (where the gravitational potential is zero) to that point. The unit is J kg^-1
Escape velocity
The minimum launch velocity required to move an object from that point to infinity
