CH18 Flashcards
(14 cards)
Gravitational fields extend to _____
Infinity
Define gravitational field strength
The gravitational force exerted per unit mass, on a small object placed at that point within a field
What is the formula for gravitational field strength
.g = -GM/r^2
Why is gravitational field strength, g, negative?
It shows that the field strength at that point is in the opposite direction to the displacement r from the centre, acts towards the centre
What is Kepler’s first law
The Orbit of a planet is an ellipse with the sun at one of the 2 foci
What is Kepler’s second law
A line segment joining a planet and the sun sweeps out equal areas during equal intervals of time
What is Kepler’s third law
The square of the orbital period T of a planet is directly proportional to the cube of its radius
What are the characteristics of a geostationary orbit
Stays in the same point above earth whilst the earth rotates
Must be in an orbit above the earth’s equator
Rotate in the same axis
Define gravitational potential, Vg
The work done per unit mass to move an object to that point from infinity. (J/kg)
When is Vg maximum and what is its value?
It is maximum at infinity, where its value is taken to be 0
Why is Vg negative
It shows that the gravitational potential is always negative. T
Negative work is being done to bring the mass in from infinity
Define Gravitational potential energy
The work done to move the mass from infinity to a point in a gravitational field
What is the area under a force/radius graph
Area= work done
