gravitational fields Flashcards
what is gravity
universal attractive force that acts between all matter
what are field lines due to
objects having mass
what do gravitational field lines represent
the direction of a field and the strength of the field depending on the density of field lines
what is gravitational field strength
force per unit mass
g = f/m
where is the mass concentrated
in the centre
what happens to field lines close to the surface of the earth
they are uniform, equally spaced and almost parallel
equation for gravitational force
g = -GmM/r^2
what is g
g is the force per unit area in a uniform gravitational field
how to derive g = GM/r^2
use
F = -GMm/r^2, g = f/m
newtons law of gravitation
two point masses attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
keplers first law
orbit of a planet is an ellipse with the sun at one focus
keplers second law
line segment joining a planet and the sun sweeps out equal areas during intervals of equal time
keplers third law
the square of the orbital period T is proportional to the cube of the average distance r from the sun, this can be proved by considering the forces acting on the planet
derive keplers third law
use GMm/r^2 and mv^2/r
what are geostationary orbit
- orbital period of 24 hours, same direction of rotation as earth
- equatorial orbit
- remain fixed in sky to observer
