Paper 1 COPY

Question 1

how do particles in an ideal gas behave

Answer 1

• 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

Question 2

Keplers first law

Answer 2

the orbit of a planet is an ellipse with the sun at one focus. the motion can be modelled as circular

Question 3

Keplers second law

Answer 3

a line segment joining a planet and the sun sweeps out equal areas during intervals of equal time

Question 4

Keplers third law

Answer 4

the square of the orbital period is proportional to the cube of the average distance r from the sun

Question 5

satellites

Answer 5

objects that orbit other larger objects

Question 6

geostationary satellites

Answer 6

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

Question 7

gravitational potential

Answer 7

work done per unit mass to move an object to that point from infinity

Question 8

escape velocity

Answer 8

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.

Question 9

planet

Answer 9

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

Question 10

dwarf planets

Answer 10

plants where the orbit has not been cleared of other objects

Question 11

asteroids

Answer 11

objects which are too small and uneven in shape to be planets

Question 12

comets

Answer 12

irregularly sized balls of rock dust and ice. orbit the sun in eccentric elliptical orbits

Question 13

solar systems

Answer 13

systems conrtaining stars and orbiting objects like planets

Question 14

galaxies

Answer 14

a collection of stars, dust and gas. Each galaxy contains around 100 billion stars

Question 15

what are nebulae

Answer 15

gigantic clouds of dust and gas and are the birthplace of all stars

Question 16

how do stars form?

Answer 16

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

Question 17

what is a protostar

Answer 17

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

Question 18

what initially happens to a star

Answer 18

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

Question 19

difference between larger stars

Answer 19

they are hotter and undergo fusion faster using up more available hydrogen, therefore have a shorter main phase,

Question 20

evolution of a low mass star to red giant

Answer 20

0.5m-10m, once hydrogen drops the gravity forces overcome radiation and gas so star begins to collapse inwards, turn into a red giant, the core of the red giant is too cool and the outer shell allows fusion to occur

Question 21

from red giant to white dwarf

Answer 21

evolved into a white dwarf outer shells drift off as planetary nebula, core remains very dense, has temperature around 3000k no fusion occurs.

Question 22

what stops white dwarfs collapsing

Answer 22

electron degeneracy pressure (as two electrons cannot exist in the same state)

Question 23

what is the Chandrasekhar limit

Answer 23

as long as the core mass is below 1.44M the white dwarf star is stable

Question 24

evolution of a massive star

Answer 24

> 10M, hydrogen depletes helium fusion occurs into heavier elements forming a red supergiant.

Question 25

what is the red supergiant

Answer 25

has layers of increasingly heavy elements produced from fusion with an inert iron core, the star becomes unstable. a type 2 supernova occurs where there is a shockwave which ejects the materials in the outer shells out in to space and the core collapses

Question 26

what happens to a collapsed type 2 supernova

Answer 26

elements heavier than iron are formed in supernovas, if the remaining mass is greater than 1.44M, protons and electrons form neutrons. This makes a neutron star, if the mass is greater than 3M the gravitational forces are so strong the escape velocity of the core is greater than the speed of light, this is a black hole.

Question 27

What are electron levels

Answer 27

bound to an atom can only exist in certain discrete energy levels, each element has its own set of energy levels. when an electron is excited it moves up when it is the opposite it moves towards the down state, releases photon with a specific wavelength

Question 28

emission line spectra

Answer 28

each element produces a unique emission line spectrum because of the unique set of energy levels associated with its electron

Question 29

continuous line spectra

Answer 29

all visible wavelengths of light are present produced by heated solid metals

Question 30

absorption line spectra

Answer 30

dark spectral lines against background of the continuous spectrum with each line corresponding to a wavelength of light used to excite atoms of that element.

Question 31

diffraction grating

Answer 31

regularly spaced slits that can diffract light, different colours of light have different wavelength have different wavelengths so will be directed at different angles.
dsinx = n(lamda)

Question 32

Weins law

Answer 32

the black body radiation curve for different temperatures peaks at a wavelength inversely proportional to the temperature of the object. where lamda is the wavelength of light produced with maximum intensity, T is the absolute surface temp

(lamda)(temp) = 2.9x10^-3

Question 33

stefans law

Answer 33

for a black body, the total radiant heat energy emitted from a surface is proportional to the fourth power of its absolute temperature.
used to relate temp with luminosity

Question 34

distances

Answer 34

Astronomical Unit = 1.5 x 10^11 average distance from earth to sun
light year = light travels in one year

Question 35

arc minutes and arcseconds

Answer 35

one degree there are 60 arc minutes and 3600 arc seconds

Question 36

what is a Parsec

Answer 36

the distance at which a radius of 1 AU subtends an angle of 1 arcsecond in metres, 1 Parsec is 3.1x10^16

Question 37

what is parallax

Answer 37

can be used to measure the distance to nearby stars, it is the apparent shift in position of an object against a backdrop of distance objects that dont appear to move accurate up to 100pc

Question 38

cosmological principle

Answer 38

the universe is isotropic (same in all directions no centre or edge) and homogenous, and the laws of physics are universal.

Question 39

doppler effect

Answer 39

apparent shift in wavelength occurring when the source of the waves is moving. if moving to detector wavelength appears to decrease, otherwise contrary

Question 40

Doppler effect in starlight

Answer 40

shifts the position of spectral lines, can be used to determine relative speed of a star
∆wavelength/wavelength = v/c

Question 41

Hubbles law

Answer 41

recessional velocity of a galaxy is proportional to its distance from earth, further away the star the faster it is moving away from us V = Hd

Question 42

universes expanding Hubbles law

Answer 42

all light from distant galaxies are red shifted showing they are moving away from earth fabric of space time expanding

Question 43

Big Bang theory evidence

Answer 43

all objects were initially contained in a singularity which suddenly expanded outwards.
- microwave background radiation
originally high energy gamma photons were distributed across the universe

Question 44

evolution of universe

Answer 44

10^-35 s = universe expands rapidly with accerlation known as inflation. no matter only high energy gamma photons and em radiation
10^-6 s =first fundamental particles gain mass
10^-3 s =most mass is created using pair production hadrons come from quarks
1s = production of mass halted

Question 45

dark energy

Answer 45

used to explain the accelerating expansion and should make up 68% of the total energy in the universe