3: Orbits and Gravity Flashcards
the measure of the motion of a rotating object in terms of its speed and how widely the object’s mass is distributed around its axis
angular momentum
the point in its orbit where a planet (or other orbiting object) is farthest from the Sun
aphelion
the point in its orbit where an Earth satellite is farthest from Earth
apogee
the region of the solar system between the orbits of Mars and Jupiter in which most asteroids are located; the main one extends from 2.2 to 3.3 AU from the Sun
asteroid belt
the ratio of the mass of an object to its volume
density
in an ellipse, the ratio of the distance between the foci to the major axis
eccentricity
a closed curve for which the sum of the distances from any point to two points inside (foci) is always the same
ellipse
the speed a body must achieve to break away from the gravity of another body
escape speed
one of two fixed points inside an ellipse from which the sum of the distances to any point on the ellipse is constant
focus (foci)
the mutual attraction of material bodies or particles
gravity
Kepler: each planet moves around the Sun in an orbit that is an ellipse, with the Sun at one focus of the ellipse
Kepler’s first law
Kepler: the straight line joining a planet and the Sun sweeps out equal areas in space in equal intervals of time
Kepler’s second law
Kepler: the square of a planet’s orbital period is directly proportional to the cube of the semimajor axis of its orbit
Kepler’s third law
the maximum diameter of an ellipse
major axis
a measure of the amount of material within an object
mass
the measure of the amount of motion of a body - the product of its mass and velocity
momentum
Newton: every object will continue to be in a state of rest or move at a constant speed in a straight line unless it is compelled to change by an outside force
Newton’s first law
Newton: the change of motion of a body is proportional to and in the direction of the force acting on it
Newton’s second law
Newton: for every action there is an equal and opposite reaction (the mutual actions of two bodies upon each other are always equal and act in opposite directions)
Newton’s third law
the path of an object that is in revolution about another object or point
orbit
the time it takes an object to travel once around the Sun
orbital period (P)
the speed at which an object (usually a planet) moves around the mass of another object; in the case of a planet, the speed at which it moves along its ellipse
orbital speed
the point in its orbit where an Earth satellite is closest to Earth
perigee
the point in its orbit where a planet (or other orbiting object) is nearest to the Sun
perihelion
a small disturbing effect on the motion or orbit of a body produced by a third body
perturbation
an object that revolves around a planet
satellite
half of the major axis of a conic section, such as an ellipse
semimajor axis
the speed and direction a body is moving (ex. 44 kilometers per second toward the north galactic pole)
velocity
