Chapter 18 - Gravitational Fields Flashcards
(15 cards)
State Newton’s 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 their separation. (F=-GMm/r²)
What does it mean if gravitational field lines are close together?
The gravitational field is strong.
Define gravitational field strength.
The gravitational force exerted per unit mass on a small object placed at that point within the field.
What is a uniform gravitational field?
Field strength does not change depending on position.
State Kepler’s First Law.
The orbit of a planet is an ellipse with the sun at one of its two foci.
State Kepler’s Second Law.
A line segment joining a planet & its sun sweeps equal areas during equal intervals of time.
State Kepler’s Third Law.
The square of a planet’s orbital period is directly proportional to the cube of its average distance from the sun. (T²∝r³)
Describe a geostationary orbit.
The orbiting object remains above the same point of the planet at all times.
What are geostationary satellites commonly used for?
GPS, local communication.
Define gravitational potential.
The work done per unit mass required to move an object from infinity to a point in a gravitational field.
Define gravitational potential energy.
The work done required to move an object from infinity to a point in a gravitational field.
Why are gravitational potential and gravitational potential energy always negative?
Gravitational force is always attractive and Vg = 0 at infinity.
What is escape velocity?
The minimum velocity for an object to escape a gravitational field.
What are the two requirements for a geostationary orbit?
-Equatorial orbit
-Object’s period of rotation is the same as the planet’s
Define gravitational field strength.
Force exerted per unit mass at a point within a gravitational field.
