- Created by: Megan mcHarron
- Created on: 19-10-18 09:23
Newton’s law of gravitational force F:
‘Any two point masses attract each other with a gravitational force that is directly proportional to the product of their masses and inversely proportional to the square of their separation.’
Kepler’s 3rd law:
Kepler showed that, for a planet orbiting the Sun, the relationship between the orbital time period T and the orbital radius r is given by:
Orbital time period:
Gravitational field strength g:
The strength of a gravitational field at a point is the force per unit mass (acting on a test mass placed at that point in a field).
( For small heights (h) : acceleration due to free fall and gravitational field strength are the same.)
gravitational field strength in a radial field:
gravitational field lines:
These represent the magnitude and direction of force per unit mass at a point in a field.
Field is always attractive, hence arrows point towards the centre of mass
Perpendicular to field lines.
V=0 at infinity.
So potential values are always negative.
Gravitational potential V:
The gravitational potential V at a point is the
work done ΔW per unit mass m
(or the change in potential energy ΔE_per unit mass m)
to move a mass m from infinity to that point.
Change in Gravitational potential energy or work done