5.4 Flashcards
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 a small mass would move when placed at that point in the field
Gravitational field strength
Force acting per unit mass at that point
Newton’s law of gravitation
The gravitational force of attraction between two point masses is directly proportional to the product of their masses and inversely proportional to the square of their separation
Kepler’s third law
The square of the period of a planet orbiting the sun is proportional to the mean radius of its orbit cubed. (Applies to other planetary systems)
Geostationary orbit
An orbit of the Earth made by a satellite that has the same time period and orbital direction as the rotation of the Earth and is in the same equatorial plane
Gravitational potential
The work done in moving a unit mass from infinity (where the gravitational potential is 0) to a given point
Gravitational potential energy
The gravitational potential of a mass at a position in the field
Escape velocity
The minimum launch velocity required to move an object from a point in a field to infinity
What are geostationary satellites used for?
Broadcasting TV signals and relaying mobile telephone signals
Monitoring the weather and changes in the environment
Monitoring air traffic
What are Kepler’s 3 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
The time period of the orbit squared is properly to the mean radius of the orbit cubed
