Chapter 18 - Gravitational Fields Flashcards
Gravitational Attraction
The force caused by objects that have mass. It can be shown as a radial field around a point mass.
When is a gravitational field uniform?
When the field lines are parallel and equidistant
Force equation
F = -GMm/r^2
Where G is the gravitational constant, M and m the two masses and r the distance between the objects
Multiple objects
Add and subtract the gravitational forces between each pair of objects on each object based on direction
G
6.67 x 10^-11 Nm^2kg^-2
Non-parallel forces
Find the force in each direction and use pythag/trig to find the resultant force
Gravitational field strength a distance from the centre of an object
g = -GM/r^2
g = -GM/r^2 derivation
Substitute F = mg into F = -GMm/r^2
Kepler’s First Law
The orbit of a planet is an ellipse with a star at one of the two foci
Kepler’s Second Law
Two line segments joining a planet and a star sweep out an equal area in equal time
Kepler’s Third Law
The square of the orbital period, T, of a planet is directly proportional to the cube of its average orbital radius, r, about the Sun
Kepler’s Third Law Formula
T^2 = (4π^2/GM)r^3
1AU
The distance from the Earth to the Sun
Speed of a satellite
v = root(GM/r)
Uses of satellites
Communication, weather and climate monitoring, GPS
