Gravitational Field Flashcards
What is gravity?
An attraction force that acts between any two masses
What are the attributes of a gravitational field
- it always attracts and never repels
- the field is not uniform (never parallel or equi-spaced) as you move away the strength of field reduces
-always attracts inwards/downward towards earths center
What is Newton’s Law of gravitation? It’s equation?
Every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them. It acts along the line joint the two particles
F = Gm1m2/r^2
Where G is gravitational constant
G = 6/67 x 10^-11 nm^2/kg^2
how is acceleration for gravitational field calculated?
Acceleration g, = Fgrav/m
g = -GMm/r^2/m = -GM/r^2
Earth: g = G x Me /R^2E
What is the behaviour of gravitational field lines?
The field lines run in the direction that a mass would be accelerated in initially.
The closer the field lines are together, the denser the gravitational field.
How do you calculate gravitational force with distance from centre of the sphere?
Fgrav = -Gm(4/3)(pie)pr^3/r//62
= -(4/3)(pie)Gpmr
what is the equation for gravitational potential?
Vgrav = Egrav/m = -Gmm/r/m = -GM/r
Egrav = mgΔh
Vgrav = gΔh
E grav = -GMm/r
What is the equation for escape velocity?
vescape = √2GM/R
Describe how satellites rotate around the earth and stays in orbit
A satellite is put into orbit by accelerating it to a sufficiently high tangential speed.
If the speed is too high, it will escape.
If it is too low, it will return to Earth.
A satellite keeps in orbit due to its high speed.
It is accelerating towards the earth due to the gravity.
Its high tangential speed keeps it in orbit.
What is the equation for orbital velocity?
Vo = √gR
What is Kepler’s 3rd Law?
The square of the orbital period of a planet is directly proportional to the cube of the semi major axis of its orbit.
T^2 ∝ R^3
What is the equation for orbital radius of the geo-stationary satellite?
Check online. Cannot incude in flashcard
How is the energy of an orbiting satellite calculated?
Check online. Cannot incude in flashcard
