Gravitational fields Flashcards
Gravity
a universal attractive force. It is considered to be a weak force, and has an infinite range.
Gravitational field strength
force per unit mass
Uniform gravitational field
The gravitational field strength does not change
What does Newton’s law of gravitation states, for the force between 2 point masses? (2)
- Force is directly proportional to the product of the masses
- Force is inversely proportional to the square of their separation
What can be seen for g in a radial field? (2)
- g is directly proportional to the mass of the object creating the gravitational field
- g is inversily proportional to the square of the distance from the center of mass of the object
Kepler’s first law
The orbit of a planet is an ellipse with the Sun at one of the two focal
Aphelion
The furthest point from the Sun
Perihelion
The closest point to the Sun
Eccentricity
A measure of how elongated the circle is
Kepler’s second law
A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time
Kepler’s third law
The square of the orbital period T of a planet is directly proportional to the cube of its average distance r from the Sun
Why do satellites not fall on the Earth even though they are constantly falling onto it?
They are traveling at a high speed → it travels a big distance as it falls on the earth it curves beneath it
What is the correct speed (v) a distance (r) for a satellite?
v=sqrt((GM)/r)
Why does the mass not matter for the perfect speed of a satelite?
Above atmosphere, no air resistance
Advantage of a polar orbit
After a certain time covers the whole of the Earth’s surface, useful for mapping purposes
