gravitation Flashcards
what are gravitational fields look like
- radial (non-uniform) field: field lines are radially inwards towards the point mass or centre of the sphere
- uniform: field lines are parallel evenly distributed towards the surface
should know the graphs from note
what is a point mass (dont need to define)
a mass that the gravitational force acts on that is has negligible size comparing to the environment, therefore thought to be a point (dont need to define)
what is newton’s law of gravitation
The gravitational force between two point masses is proportional to the product of the masses and inversely proportional to the square of their separation
newton’s law of gravitation equation
Fg = GMm/r^2
what is G
gravitational constant (given in exam)
how to measure r (in gravitation)
from the centre of one object to the centre of the other
circular motion of planets orbits is cause by what force
gravitational force is the centripetal force in this case
what is geostationary orbit
- directly above equator
- always orbit same point with earth
- orbit from west to east
- period of 24 hours
define g gravitational field strength jkg^-1
The force per unit mass of a gravitational force on an object
formula of g
g = F/m = (G*M)/r^2
why is gravitational strength (g) on surface of earth constant
because compare to the distance of earth’s radius, the height change is negligible
define gravitational potential φ
the work done per unit mass in bringing a small test mass from infinity to the point in a gravitational field
equation for φ
φ = - Gm / r
define gravitational potential energy
the work done to assemble the system from infinite separation of the component of the system
unit of φ
Jkg^-1
∆φ equation
∆φ = φf - φi = - GM/rf - (- GM/ri)
= -GM (1/rf - 1/fi )
equation for Ep(gravitation)
Ep = - GMm/r
∆Ep equation
∆Ep = GMm (1/ri - 1/rf)
what is work done in a gravitational field
∆Ep
when to use ∆Ep = mgh
only for uniform gravitational field
