gravitational fields Flashcards
what is gravitational field strength (g)
The gravitational force exerted per unit mass
n a small object placed in that field
vector quantity
gravitational field strength of an object is the same as
the acceleration of free fall of that object
a stronger field is represented by field lines that are…
closer together
what is a radial field
where the field lines are around a spherical mass
what is a uniform gravitational field
where the field lines are parallel and equidistant
the gravitaional field stength does not change
newtons law of gravitation
The forces between two point masses are
- directly proportional to the product of the masses
F ~ Mm
- inversely proportional to the square of their separation
F ~ 1/r sqaured
G
Gravitational constant used in newtons law of gravitation
Kepler’s first law
the orbit of a planet is an ellipse with the sun at one of the two loci
(in most cases the orbits have low eccentricity so their orbits are just modelled as circles)
what is an aphelion and perihelion
aphelion is the furthest point from the sun in an orbit
perihelion is the closest point from the sun in an orbit
keplers third law
the square of the orbital period of the planet is directly proportional to the cube of the average distance from the sun
keplers second law
a line segment joining a planet and the sun sweeps out equal area in the same time
uses of satellites
communication
military uses
scientific research (pollution etc)
what are geostationary satellites
-satellites placed in orbit above the equator
- rotate in the same direction as the earth rotates
- have an orbital period of 24 hours
gravitational potential definition
the work done per unit mass to move an object from that point to infinity
negative as the gravitational potential at infinity is 0
