revision cards

Question 1

define acceleration

Answer 1

Acceleration is the rate of change of velocity ie an acceleration of 5 ms-2 means the velocity is
increasing by 5 ms-1 every second

Question 2

what are satelites

Answer 2

satelites are in freefall around a planet or star. They are constantly accelerating but not changing speed. this is because of direction, not the magnitude of their velocity is changing. the surface of the planet or star curves away from the satellite at the same rate the satelite curves towards it hence the satelite remains in orbit at a constant altitude

Question 3

what are the rules for projectiles

Answer 3

o The first job is usually to resolve the initial velocity into components (uhorizontal = u cosθ and
uvertical = u sinθ where θ is the angle to the horizontal)

o From now on only use the components uh and uv

o Horizontal velocity is constant (use sh = vh t)

o Vertical acceleration is constant due to gravity (use sv uv vv av t and watch your negatives).

Question 4

define newtons first law

Answer 4

newtons first law states that an object will remain at rest or move with a constant speen in a straight line (constant velocity) unless acted upon by an unbalanced force

Question 5

newtons second law

Answer 5

F = ma.

Question 6

newtons third law

Answer 6

states that for every action there is an opposite and equal reaction. punch a wall and the force of my fist on the wall is equal to that of the wall on my fist

Question 7

friction

Answer 7

force that always acts opposite to an objects motion

Question 8

tension

Answer 8

pulling force, acts both ways at same time

Question 9

air resistance

Answer 9

increases with speed. what makes an object eventually reach terminal velocity

Question 10

scales in a lift

Answer 10

scales measure the force acting upwards on a person

Question 11

slopes

Answer 11

The component of weight acting down a slope = m g sinθ where θ is the angle of the slope
to the horizontal.

Question 12

define the conservation of momentum

Answer 12

states that the total momentum before a
collision/explosion is equal to the total momentum after the collision/explosion as long as no
external forces are acting

Question 13

what is an elastic collision vs an inelastic collision

Answer 13

Elastic collision: Kinetic energy is conserved. Inelastic collision: Kinetic energy is NOT conserved.

in both momentum is conserved

Question 14

impulse

Answer 14

the change in momentum = area under a force time graph. this takes place when there is a net external force. Ns

Question 15

gravity Qs

Answer 15

remember to measure from center of one mass to center of the other

Question 16

relativity - what is time dialation and length contraction

Answer 16

The speed of light in a vacuum is the same for all observers.

Time dilation is the increase in an observed time interval for an object moving relative to an
observer compared to that measured when they are in the stationary frame of reference.

Length contraction is the decrease in the observed length (in the direction of motion) of an object
moving relative to an observer compared to that measured when they are in the stationary frame
of reference.

t and l are when the observer and object are stationary relative to each other, ie they are in the
same location, and t’ and l’ are when there is relative motion, ie things are observed in more than
one location.

Question 17

Evidence supporting the Big Bang/expanding universe theory

Answer 17

Cosmic Microwave Background Radiation
the abundance of hydrogen and helium
the darkness of the sky (Olbers’ paradox) - if universe infinite should be stars in all parts of the night sky
the large number of galaxies showing redshift rather than blueshift.

Question 18

dark matter

Answer 18

the mass of a galaxy can be estimated using the orbital speed of their stars

Masses measured are bigger than those predicted by looking at the number of stars present

conclusion is that there must be matter we cant see - Dark matter

Question 19

Dark energy

Answer 19

supported by the accelerating rate of expansion of the universe ie something appears to be opposing gravity

Question 20

hotter the star is the

Answer 20

shorter the peak wavelength of emitted radiation (more blue)

the more energy it emits per m^2

Question 21

what is the longest and shortest wavelengths of visible light and what colours do they appear as

Answer 21

380 - 700 nm

380 is violet and 700 is red

Question 22

Standard Model

Answer 22

12 Fermions (matter particles)

6 Quarks – up, down, charm, strange, top, bottom

6 Leptons – electron, electron neutrino, muon, muon neutrino, tau, tau neutrino

4 Gauge Bosons (force carriers)

photon (electromagnetic force)

Z and W± bosons (weak nuclear force)

gluon (strong nuclear force)

Question 23

Hadrons

Answer 23

made up of quarks

Baryons are made of 3 quarks eg protons, neutrons

Mesons are made of 2 quarks (a quark and an anti-quark) eg pions, kaons

Question 24

strong force

Answer 24

Strong force holds quarks together and also holds protons and neutrons together in the nucleus

Question 25

beta decay

Answer 25

Beta decay is caused by the weak force and is evidence of the Neutrino beta minus decay consists of a neutron is affected by the weak force and one of its down quarks turns into an up quark becoming a proton . to conserve charge an electron is emitted aswell as an anti neutrino beta plus decay - proton affected by the weak force turns into a neutron (up quark turns to down quark). releasing an anti electron (positron) and a nuetrino

Question 26

what is antimatter

Answer 26

particles are identical to their corresponding matter particles except charge. if touches its matter counterpart it is annihalated

Question 27

Eletric field - what way do lines go , what particles will accelerqte and why

Answer 27

in diagram lines point from pos to neg a charged particle will accelerate in an eletric field because it experiences unbalanced forces gain in kinetic energy = work done by eletric field

Question 28

what is p.d.

Answer 28

voltage is the number of joules of energy per coulomb of charge

Question 29

magnetic feilds - what does moving a charged particle do, which way do field lines go

Answer 29

moving charged particle will produce magnetic field field lines point from north to south

Question 30

what is nuclear fusion

Answer 30

nuclear fusion is smaller parts combining to a more massive nucleus whatever mass is not converted is turned into E ------- E=mc^2

Question 31

what is fission

Answer 31

big nucleus splitting into smaller parts induced/stimulated - usually caused by bombardment with nuetrons spontaneous - random event/no trigger

Question 32

wave particle duality

Answer 32

the photoelectric effect is proof that light is a particle interference proves light is a wave

Question 33

photoelectric effect

Answer 33

clean negatively charged zinc plate exposed to high F ultra violet light discharges each photon of light gives electron energy to jump off

Question 34

light going from vacuum (air) to medium

Answer 34

speed wavelength and angle all decrease F does not change

Question 35

total internal reflection occurs when

Answer 35

the angle of incidence is greater than the critical angle

Question 36

irradiance from a point scource follows what law

Answer 36

inverse square law if you double the distance then the irradiance will quarter if you triple the distance then the irradiance will be 9 times less

Question 37

bohr model of atom

Answer 37

Eo is the ground state and lowest E level E0, E1, E2 etc have negative energy levels in comparison to the ionisation level ' ionisation level has an energy of 0 - if electron gain ionisation energy they jump off electrons gain E and jump up if they go down E they give off photon of light

Question 38

peak and rms

Answer 38

peak always bigger rms = peak over root 2 use rms values for power calc

Question 39

parallel and circuit

Answer 39

o Current in series is the same (CISS), current in parallel branches add up to supply current o Voltage in parallel is the same, voltage in across series components add up to supply voltage (VIPs use VISA …)

Question 40

t.p.d. = terminal potential difference

Answer 40

the p.d across the rest of the circuit

Question 41

ideal supplu

Answer 41

A SUPPLY with no r

Question 42

open circuit

Answer 42

infinite resistance - nothing connected across terminal supply = emf as no current so no internal resistance

Question 43

short circuit

Answer 43

no load resistance and mac current drawn

Question 44

how is r calculated

Answer 44

use a variable resistor and plot V on y and I on x r = negative gradient emf = y intercept max current = x intercept

Question 45

if more than one supply

Answer 45

combine rs and emfs

Question 46

capacitance is

Answer 46

the number of charge stored per volt

Question 47

charge against p.d. graph

Answer 47

Gradient = capacitance area under the graph = energy stored

Question 48

when capacitor is fully charged

Answer 48

p.d = supply V current = zero V across resistor = 0

Question 49

when Capacitor is fully discharged

Answer 49

V = 0 Current = max current allowed by ohms law V across R = supply V

Question 50

Current does what when charging AND discharging

Answer 50

starts large and decreases in magnitude

Question 51

Increasing R or C does what

Answer 51

increases the time taken for capacitor to charge and decreases magnitude of max current increasing C also increases the max energy stored(can also be achieved by increasing supply voltage )

Question 52

when atoms combine what happens to the electrons

Answer 52

they combine into energy bands instead of discrete energy levels

Question 53

what are the diffs between the bands

Answer 53

the fullest band is the valence band and the band above that is the conduction band. electrons are held tightly in the valence band but have room to move freely in th econduction band.

Question 54

conductors

Answer 54

have overlapping conduction and valence band so dont require energy for electrons to move across bands

Question 55

insulators

Answer 55

have a empty conduction band and an full valence band there is also a large energy gap so the electrons require large amounts of energy to jump up

Question 56

what is doping

Answer 56

adding impurities to semiconductors to reduce their resistance

Question 57

what is a semiconductor

Answer 57

like an insulator but with a much smaller band gap, the gap is small enough that at room temperature some electrons have energy to jump from valence to conduction band and increase the conductivity of the solid. conductivity increases aka resistance decreases with increasing temperature

Question 58

n-type

Answer 58

an n-type semi conductor is one that has been doped with an element with more electrons so there are extra electrons. these are added to the conduction band and allows it to conduct more. makes it negative

Question 59

p-type

Answer 59

impurities are added which have extra holes. this creates gaps in the valence band. this makes it p

Question 60

p-n junction

Answer 60

p and n type conductors are side by side. a depletion layer forms which has virtually no free charge carriers.

Question 61

forward and reverse biased

Answer 61

forward = n to negative and p to positive reverser means opposite

Question 62

solar vell

Answer 62

is an unbiased p-n junction. photons enter and give electrons enough energy to jump from valence band of p type to conduction band. moves down to the n-type and a voltage is produced. this is the photo voltaic effect

Question 63

Mrs Lindsay’s equation

Answer 63

Vr = (Rr/Rt.)xVo