Chapter 18 Gravitational fields

18.1 intro

what do all objects with mass create?

gravitational field

figure 2

all gravitational fields extend all the way to infinity, but it gets weaker as the distance from the centre of mass of the object increases, becoming negligible at long distance

any object with mass places in a gravitational field will…

experience an attractive force towards the centre of mass of the object creating the field. For objects on Earth, we call this gravitational the object’s weight

Gravitational field strength formula 

what type of quantity is gravitational field strength

a vector quantity

where does gravitational field strength always point to

the centre of mass of the object

figure 4

study tip for term gravity

how do you know when you have a uniform gravitational field

the field lines should be parallel and equidistant

what does not change in a uniform field

the gravitational field strength

figure 5

gravimetry ( not in the spec - js extra stuff ) 

18.2 intro

newton’s law of gravitation intro 

Newton’s law of gravitation states the force between 2 point masses is:

study tip

worked example: the gravitational force on an orbiting satelite

figure 3

figure 4 

figure 5

worked example: objects in 2 dimensions 

18.3 intro 

gravitational field strength in a radial field 

worked example: g on the international space station

graphical work: grav fields 

uniform gravitational fields : earth