Revision

Question 1

what is friction?

Answer 1

a force between two surfaces that impedes motion and results in heating

Question 2

what is Newton’s third law?

Answer 2

every action has an equal opposite reaction

Question 3

motion of a body falling in a uniform gravitational field

Answer 3

1. initially there is no air resistance and the only force acting on the body is weight
2. as it falls, it accelerates which increases its speed and results in air resistance
3. this causes the resultant force downwards to decrease
4. therefore the acceleration decreases, so it is not speeding up as quickly
5. eventually they are equal and opposite and balance so there is no resultant force
6. so there is no acceleration and terminal velocity is reached

Question 4

what is elastic deformation?

Answer 4

when the object returns to its original shape when the load has been removed

Question 5

what is a moment?

Answer 5

the moment of a force is a measure of its turning effect

Question 6

what is moments measured in?

Answer 6

Nm

Question 7

when is an object in equilibrium?

Answer 7

when the sum of clockwise moments equals the sum of anticlockwise moments and there is no resultant force

Question 8

what is the principal of momentum?

Answer 8

the total momentum before is equal to the total momentum afterwards

Question 9

what is potential difference?

Answer 9

the work done per unit charge in moving in between two points in a circuit

Question 10

the higher the potential difference…

Answer 10

the greater the current

Question 11

what happens in an ohmic conductor?

Answer 11

the current is directly proportional to the voltage

Question 12

why is a filament lamp non-ohmic?

Answer 12

as the current increases through the filament, the temperature increases, which means electrons and ions vibrate more and collide more, increasing resistance

Question 13

how does an inkjet printer work?

Answer 13

• droplets of ink are charged and pass between two charged metal plates, one of which has a positive charge and the other a negative charge
• the droplets are attracted to the plate with the opposite charge and repelled by the plate with the same charge and deflected towards a specific spot on the paper

Question 14

how does a photocopier work?

Answer 14

• the image of a document is projected onto a positively charged plate, where light falls onto the plate, the charge leaks away
• negatively charged toner particles are attracted to the remaining positive areas
• paper is then placed over the plate and toner is transferred to it, making the photocopy

Question 15

amplitude definition

Answer 15

the distance from the equilibrium position to the maximum displacement

Question 16

wavefront definition

Answer 16

the joining points on a wave at the same point in their wave cycle at a given time

Question 17

frequency definition

Answer 17

the number of waves that pass a single point per second

Question 18

wavelength definition

Answer 18

the distance between a point on one wave and the same point on the next wave

Question 19

time period definition

Answer 19

the time taken for one complete wave to pass a fixed point

Question 20

when does TIR occur?

Answer 20

when the angle of incidence is greater than the critical angle and the light reflects back into the medium - the light must be travelling from a more optically dense to a less optically dense medium

Question 21

what is an optic fibre and what is it used for?

Answer 21

• a long thin rod of glass surrounded by cladding which uses TIR reflection to transfer information by light
• used in medicine e.g. endoscopes and communications e.g. high speed data transfer

Question 22

what is an oscilloscope connected to and what does it measure?

Answer 22

microphone - sound wave

Question 23

the greater the amplitude is…

Answer 23

the louder it is

Question 24

the greater the frequency is…

Answer 24

the higher its pitch

Question 25

microwave uses

Answer 25

satellite transmissions and cooking

Question 26

infrared radiation uses

Answer 26

heaters and night vision equipment

Question 27

radio wave uses

Answer 27

radio and TV communications

Question 28

what bodies are good for what?

Answer 28

black bodies with dull texture = best absorbers and emitters white bodies with shiny texture = best reflectors

Question 29

when is work done?

Answer 29

when a force moves something through a distance

Question 30

what is evaporation?

Answer 30

escape of molecules with higher energy from surfaces of liquids

Question 31

what is specific heat capacity?

Answer 31

the amount of energy required to raise the temperature of one kilogram of mass of a substance by 1 degrees C

Question 32

how do gases exert pressure on a container?

Answer 32

- when the molecules rebound off walls, they change direction so their velocity and therefore momentum changes - this means they exert a force because force is equal to change in momentum/time

Question 33

how to convert celcius into kelvin?

Answer 33

celcius + 273

Question 34

how is voltage transformed in a step down transformer?

Answer 34

- step down decreases voltage - current in primary coil produces magnetic field - current is alternating - causes a magnetic field in the iron core - the core strengthens the field - field lines interact with the secondary coil - induces a voltage in the secondary coil - transformers won’t work with direct current

Question 35

what is radioactive decay?

Answer 35

the spontaneous transformation of an unstable nucleus into a more stable one by the release of radiation

Question 36

alpha decay

Answer 36

- heavy nucleus emits an alpha particle - highly ionising - weakly penetrating - stop by thin sheet of paper

Question 37

beta decay

Answer 37

- a neutron turns into a proton and emits a beta particle (electron) - moderately ionising - moderately penetrating - stopped by thin sheet of aluminium

Question 38

gamma decay

Answer 38

- a nucleus with excess energy emits a gamma particle - lowly ionising - highly penetrating - stopped by many cm of lead

Question 39

neutron radiation

Answer 39

- in neutron rich nuclides, one or more neutrons are ejected - also emitted during nuclear fission

Question 40

three sources of background radiation

Answer 40

- cosmic rays - radon gas - fallout from nuclear weapons testing

Question 41

nuclear fission

Answer 41

a uranium-235 nucleus absorbs a thermal neutron, it splits into two daughter nuclei and 2 or 3 neutrons, releasing energy in the process

Question 42

nuclear fusion

Answer 42

process of fusing two nuclei to form a larger nucleus - there is very small loss of mass in the process, accompanied by a release of energy

Question 43

why does nuclear fusion not happen at low temperatures or pressures?

Answer 43

- nuclei move two slowly at low temperatures - they collide less often - they repel each other - nuclei can’t get close enough to fuse

Question 44

what is gravitational field strength measured in?

Answer 44

N/kg

Question 45

stellar evolution of a star same size as sun

Answer 45

protostar -> main sequence star -> red giant -> white dwarf -> black dwarf

Question 46

stellar evolution of a star bigger than the sun

Answer 46

protostar -> main sequence star -> red giant -> supernova -> black hole or neutron star

Question 47

what is absolute magnitude?

Answer 47

equal to the apparent magnitude that the star would have if it were viewed from exactly 10 parsecs away

Question 48

what is apparently magnitude?

Answer 48

how bright a star appears at a particular point in space

Question 49

what does a HR diagram show?

Answer 49

relationship between stars surface temperature and brightness

Question 50

position of components on a HR diagram

Answer 50

supergiants = top right red giants = below supergiants main sequence = diagonal strip white dwarf = bottom left

Question 51

evidence for big bang theory

Answer 51

MP1. identification of cosmic (microwave) background radiation (CMBR); MP2. CMBR appears to be the same in all directions/is everywhere; MP3. which implies all parts of the Universe were In contact a long time ago; MP4. wavelength has increased as the universe has expanded; MP5. universe was (significantly) hotter long ago MP6. identification of red shift of galaxies; MP7. the further the galaxy is (from Earth), the greater the red-shift; MP8. larger redshift means faster movement of galaxies; MP9. (therefore the further away, the faster the galaxy moves away; MP10. galaxies moving apart from each other implies expansion from a single point or since the Big Bang;