Gravitational fields Flashcards
(13 cards)
Gravity
universal attractive force that acts between all matter
What do field lines tell you
strength of field and direction
what is g
- force per unit area in a uniform gravitational field
- radial field: proportionality constant at that point between force and mass
Newtons law of gravitation
Two masses attract eachother with a force directly proportional to the product of their masses, and inversely proportional to the square of the distance between them
Keplas first law
The orbit of a planet is in an ellipse, with the sun at one focus
Keplas second law
A line segment joining a planet and the sun, sweeps out equal areas during intervals of equal time.
(this is because the speed of the planet is not constant, moves faster when closer to the sun)
Keplas third law
T^2 is proportional to average distance r^3 from the sun
What are satellites and their use?
- objects that orbit other objects (including moons)
- GPS, communications and scientific research
What are geostationary satellites?
- orbital period of 24 hours
- appear stationary above earth
- orbit 36,000km above equator
- useful for communications and surveying as they provide continuous coverage
what is gravitational potential energy?
The work done to bring a mass from infinity to a point.
what is gravitational potential difference?
Difference in gravitational potentials between two points in a gravitational field.
what is gravitational potential?
- potential energy per kilogram at any point in the field
- 0 potential defined at infinity, so close to a mass would be negative value
What is escape velocity
Minimum velocity required for an object to escape the gravitational field, when projected vertically from its surface
- 1/2mv^2 = Gmm/r
