Gravitational Fields Flashcards
What are some properties of the gravitational force between 2 masses?
Always attractive, prop to product of masses, follows an inverse square law
What is a force field?
A region in space where objects experience non-contact forces
How do you find acceleration in a grav field?
Combine g = F/m and F = ma to get a = g
How do you find the field strength for a radial grav field?
Combine g = F/m and F = Gm1m2 / r^2 to get g = GM/r^2.
What is the grav field strength at the surface for a planet of radius R?
g = GM / R^2
What is the grav potential energy at a point in a grav field?
E(p) = Vm = -GMm / r, for a mass m in a field caused by a mass M
What are the units of grav potential?
Jkg^-1
Where is grav. potential zero?
At an infinite distance away from a mass.
Why is grav. potential always negative?
As work must be done to move objects apart, but Ep can only have a max of zero, so grav. potential must always be negative.
How do you find change in grav potential?
Area under the graph of g against r
Where is g (field strength) largest?
At the surface of a planet.
What is the work done moving along an equipotential?
0J
What is the potential gradient in a field?
Change in potential per metre, potential grad = change in V / change in r
How is grav field strength related to potential gradient?
g = -delta V / delta r. So g can be found from a gradient of a V against r graph.
What is the escape velocity?
The minimum energy an object must be given to escape a body’s grav field. So must be energy used to move from infinity to the surface.