Paper 1 COPY Flashcards
how do particles in an ideal gas behave
- gas contains large number of atoms with brownian motion
- volume is negligible when compared to the total volume of the gas
- all collisions are perfectly elastic
*time taken for atoms to collide is negligible compared to the time between collisions - electrostatic forces between atoms are negligble except when colliding
Keplers first law
the orbit of a planet is an ellipse with the sun at one focus. the motion can be modelled as circular
Keplers second law
a line segment joining a planet and the sun sweeps out equal areas during intervals of equal time
Keplers third law
the square of the orbital period is proportional to the cube of the average distance r from the sun
satellites
objects that orbit other larger objects
geostationary satellites
have an orbital period of one day they travel in the same direction as the rotation of the earth along the equatorial plane. therefore remaining above the same point on earth
gravitational potential
work done per unit mass to move an object to that point from infinity
escape velocity
for an object to escape a gravitational field produced by a mass M the kinetic energy of the object at the start must be equal to or greater than the gravitational potential energy required to lift it to infinity.
planet
objects with mass sufficient for their own gravity to force them to take a spherical shape where no nuclear fusion occurs and the object has cleared its orbit of other objects
dwarf planets
plants where the orbit has not been cleared of other objects
asteroids
objects which are too small and uneven in shape to be planets
comets
irregularly sized balls of rock dust and ice. orbit the sun in eccentric elliptical orbits
solar systems
systems conrtaining stars and orbiting objects like planets
galaxies
a collection of stars, dust and gas. Each galaxy contains around 100 billion stars
what are nebulae
gigantic clouds of dust and gas and are the birthplace of all stars
how do stars form?
over years the gravitational attraction between dust and gas particles pulls them together to form clouds. some regions become denser and pull in more dust and gas due to the gravitational collapse. the gravitational energy is converted to thermal energy. the resultant sphere of very hot dense dust and gas is a protostar
what is a protostar
for a start to form the temp and pressure must be high enough for the hydrogen gas nuclei in the protostar to overcome the electrostatic forces of repulsion and undergo nuclear fusion this produces helium nuclei producing a star
what initially happens to a star
remains in stable equilibrium the gravity forces act to compress the star but radiation pressure from photons emitted in fusion and gas pressure within the core counteract this keeping the size constant. this is the main phase of the star