5.4 Gravitational fields Flashcards
Draw model of the direction of gravitational fields of a planet.
Arrows converging towards a circular object
What term is used for gravitational fields for flat surfaces of an object?
uniform
What is the definition of gravitational field strength?
The gravitational force experienced per unit mass by an object at that point in a gravitational field.
What are the units for gravitational field strength
NKg^-1
The gravitational field strength equation is only valid when?
-The masses gravitational field strength is negligble in comparison to the external gravitational field strength
What does Newtons law of gravitation state?
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
What is the purpose of the negative sign in Newtons law of gravitation?
-Used to show the attractive nature of the force
What is the purpose of the second gravitational field equation?
It shows the gravitational field strength for a point mass of one object
What does Kepler’s 1st law state?
the orbit of a planet is an ellipse, with the sun at one focus
What does Kepler’s 2nd law state?
a line segment joining a planet and the sun sweeps out equal areas during intervals of equal time (speed of the planet is not constant as it moves faster near the sun)
What two equations can equated to explain Kepler’s 3rd law? write it making v^2 the subject
Centripetal force = newtons force law of gravitation
v^2 = GM/r
what 2 equations link when Kepler’s 3rd law has velocity substituted for circular motion velocity?
(2pir/t)^2 = GM/r
Rearrange to make time the subject in equation of Kepler’s 3rd law
T^2= 4pi^2r^2/G*M
What is derived when making time the subject of the equation
T^2 is directly proportional to r^3
What notation is used for gravitational potential?
Vg
