ch 13 Flashcards
what is a gravitational field
a region of space where a mass experiences a force
what is gravitational field strength at a point
it is the force per unit mass acting on a small mass placed at that point
what is gravitational field lines
lines that represent the direction of the gravitational force acting on that object
what is newton’s law of gravitation
the gravitational force acting on two objects is directly proportional to the product of there masses and inversely proportional to the square of there separation noting that the radii of these masses are very small compared to the distance between them
equation of newton’s law of gravitation
f=Gmm/r^2
Kepler’s third law of planetary motion
for plants or satellites describing circular orbits about the same central body, the square of the period is proportional to the cube of the radius of the orbit
what is geostationary orbit
an equatorial orbit with exactly the same period of rotation as the earth (24 hrs) and the exact same direction of rotation as the earth (west to east) so that the orbiting satellite is always above the same point on the equator
equation field strength
g= GMlr^2
what is gravitational potential at a point in a gravitational field
defined as the work done per unit mass in bringing a small test mass from infinity to the point
what is the equation of gp
Φ = −GM/r
equation of gravitational potential energy
mΦ = −GMm/r
By reference to the definition of gravitational potential, explain why gravitational potential is a
negative quantity
potential at infinity defined is zero, (gravitational) force is attractive so work done causing object to lose potential energy as object moves from infinity (so potential is negative)
