18. Gravitational fields Flashcards
(12 cards)
What are Gravitational fields due to?
Objects having mass
What happens when an object with mass in placed in a gravitational field?
It experiences an attractive force towards the centre of mass of the object creating the field
Define Gravitational field strength
The gravitational force exerted per unit mass at a point within a gravitational field
What is the equation for gravitational field strength?
g = F/m
What type of force is gravitational force always?
Attractive
What is the equation for Gravitational force?
F = - GMm/r2
F = Gravitational force
G = Gravitational constant
M = Mass of object 1
m = mass of object 2
r = distance between objects
What is the equation for Gravitational field strength?
g = - GM/r2
M = mass of object creating gravitational field
What is the gravitational field strength like in a uniform gravitational field
Gravitational field strength does not change (distance is negligible)
What is Keplers first law?
The orbit of a planet is an ellipse with the sun at one of the two foci
What is Keplers second law?
A line segment joining a planet and the sun sweeps out equal areas during equal intervals of time
What is Keplers third law? (and the equation)
The square of the orbital period T of a planet is directly proportional to the cube of its average distance r from the sun
T^2 is directly proportional to r^3
T2/r3 = k
What is an Astronomical unit?
The mean distance from the Earth to the sun
