Physics CGP paper 1 Flashcards
1
Q
velocity displacement formula
A
v^2 = u^2 + 2as
2
Q
dont forget these forces
A
- tension
- buoyant force
- electrostatic forces
- thrust
3
Q
friction
A
- to travel at a steady speed, you need a driving force that counteracts the friction
- ## exists in solid surfaces sliding past eachother, gripping eachother (static friction), or caused by the drag in fluids
4
Q
investigating motion of a toy car
A
- you can use light gates to prevent innacuracy
5
Q
3 laws of motion
A
- balanced forces means no change in velocity
- a resultant force means acceleration -> F=ma
- If object a exerts a force on object b, object b exerts a force of equal magnitude but opposite direction
6
Q
Terminal velocity depends on shape and area:
A
- the accelerating force acting on all falling objects is gravity
- -> if not for air resistance, they would fall at the same rate
- hamsters and feathers will hit the ground at the same time at the moon (there’s no air there)
7
Q
mains and battery supply
A
- main is a.c supply, battery is d.c supply
8
Q
wire graph
A
- The current through a wire is proportional to voltage
- > half triangle sandwich
9
Q
Differing resistors graph
A
- current through a resistor is proportional to voltage
- but different resistors have differing resistances
- different gradients
- -> half sandwich in different halves
10
Q
Metal filament lamp graph
A
- as temperature of the metal filament lamp inc.
–> resistance increases
(i still don’t understand how this graph works)
11
Q
Diode graph
A
- Current will only flow through a diode in one direction
- -> flat then goes up
12
Q
light emitting diode and LDR symbol
A
- 2 arrow up, big arrow in circle -> LED
- 2 arrow down, resistor -> LDR
13
Q
Series circuit
A
- If one component is removed, the whole circuit is broken
- more cells in a series means a bigger supply p.d
- current same everywhere
- potential of supply is shared between components
- total resistance is sum of resistance of each component
14
Q
Parallel circuits
A
- one disconnected barely affect the circuit
- potential difference is the same across all branches
- current is shared between branches
- current through a branch dpeends on the resistance of a branch
- total resistance of the circuit decreases if you add a second resistor in parallel (?)
15
Q
Energy transfer formula
A
E = QIR E = QV
16
Q
Wires
A
Live -brown
Neutral - Blue
Earth - Green and yellow
17
Q
Earthing + fuses
A
- If fault develops, big current flow through the live wire, the case then the earth wire
- surge in current will blow the fuse or trip the circuit breaker
- -> cuts off the circuit
- C.B can be reset, dont have to be replaced, and are much faster
18
Q
Resistors get hot
A
- there is an energy transfer when there is an electric current (this heats the resistor)
- Electrons collide with the ions in the lattice that make up the resistor.
- ions get energy, cause vibrations, then increases thermal energy
19
Q
Transverse
A
- the vibrations are at 90 deg to the direction energy is transferred by the wave
20
Q
Longitudinal
A
- the vibrations are along the same direction as the energy transfer
21
Q
wave
A
- top n bottom is crest and trough
22
Q
2 or more waves moving together = have wavefront
A
- wavefronts are imaginary planes that cut across all the waves at a certain
- distance between each wavefront equal to one wavelength
23
Q
Doppler effect
A
Car
- Wave speed is constant. If the source is moving, it ‘catches up’ to the wave that were originally emitted.
- causes the wavefronts to bunch up in front of the moving source. Behind it, the wavefronts spread out
- frequency of a wave from a source towards you will be higher, and wavelength will be shorter than the wave prod. by the source
- therefore sounds higher pitched
24
Q
Radio waves
A
- communication, TV and radio broadcasts
- reflected from the ionosphere
25
Microwaves
- Heating in microwaves
- Satellite communication
______
- heat human body tissue, damage them INTERNALLY
26
Infrared radiation
- heating. Radiators or cooking food
- monitoring temperature -> night vision equipment
_______________
- can cause nasty skin burns
27
Light signals/Visible light
- They can travel through optical fibres through TIR
- used for medical purposes to 'see inside' the body without having to operate
- useful for photography
28
ultraviolet rays
- used in fluorescent lamps
_______________
- can damage surface cells and cause blindness
- some UV rays are 'ionising', enough energy to knock electrons off atoms. Can mutate or destroy cells.
29
X rays
- lets us see inside things
_______________
- small risk that chance of cancer increases
30
Gamma
- sterilising equipment and food
_______________
- Very ionising, can cause cell mutation/destruction
- leads to tissue damage or cancer
31
Energy stores
1. kinetic
2. thermal
3. chemical
4. gravitational potential
5. elastic potential
6. electrostatic
7. Magnetic
8. Nuclear
32
energy transfers
1. mechanically
2. electrically
3. by heating
4. by radiation (light sound waves)
33
1 example of energy transfer: ball roll up slope
1. KE store of ball transferred mechanically to its GPE store
2. Some energy is transferred mechanically to the thermal energy stores of the ball and the slope due to friction
3. energy is wasted by thermal energy stores heating the surrounding
34
Thermal conduction
- the process where vibrating particles transfer energy from their kinetic energy store to the kinetic energy stores of neighbouring particles
35
Convection
- when the more energetic particles move from the hotter region to the cooler region
- --> in an immersion heater, water gets heated and gets less dense. Rises up, displaces cold, cycle repeats (changes in density. This is a convection current)
- purple potassium permanganate crystals in cold water test for convection current
36
reduce rate of e transfer
- use insulators (includes stuff that traps pockets of air)
- black, matte better at absorbing
- white, shiny, better at reflecting
37
Particle theory
- as gas particles move about, they randomly bang into each other and whatever else gets in the way
- In a sealed container, gas particles collide with other particles to change momentum and direction, but what primarily creates the outward pressure is the collision with the container's walls
- Heat inc KE of particles. More frequent and stronger collisions. Ultimately, larger total force, therefore more pressure.
-
38
Magnets
- always north to south
| - North and south poles of 2 permanent magnets creates a uniform field between the magnets
39
magnetic field patterns (?)
- compasses, iron filings align themselves with mag fields
- for compass, put it down, note down the direction the arrow points at
- for iron filing, put the magnet under a piece of paper, and tap the paper until iron filings form a clear pattern
40
current carrying wires
- creates a magnetic field
- larger the current, stronger the magnetic field
- the direction of the magnetic field depends on direction of current
41
magnetic materials can be
- iron soft (temporary)
| - steel hard (permanent)
42
motor effect
- two magnetic fields affect one another
| - -> wire and a permanent magnet
43
speed up motor
- more current
- more coil turns
- stronger magnetic field
- soft iron core in the coil
44
split ring commutator
- swaps the contact every half turn to keep the coil rotating in the same direction. (otherwise, the coil will stay still after both sides have reach the top and bottom)
45
loudspeaker
- A.c electrical signals fed to a coil of wire in the speaker
- wrapped at a base of a cone. (This cone directs the sound)
- coil surrounded by permanent magnet
- A.C signals cause a force on the coil and make it vibrate. This is due to the motor effect.
- Vibrations create sound.
46
Dynamo effect
- electrical conductor (coil of wire) moves through a magnetic field. and vice versa
- electromagnetic induction occurs. induces current.
47
Slip rings and brushes
ensures that contacts do not swap every half turn
48
transformer
prim v/ 2nd v = prim turn / 2nd turn
49
radioactive decay
- nuclei of unstable isotopes break down at random\
| - spits out one or more types- alpha beta gamma
50
ionisation of nuclear radiation
- bashing into atoms, knocking electrons off of them due to radiation, is ionisation
51
alpha v beta
```
a.
- helium nuclei
- big heavy, therefore weak penetration
--> but therefore strong ionization
- positive, deflects positive
___
STOPPED BY PAPER, SKIN, FEW CM AIR
e.
- electron
- fast, small. moderate penetration
--> moderate ionization
- deflect negative
___
STOPPED BY FEW CM ALUMINUM
```
52
gamma
- highly penetrating. Only energy, no mass.
--> eventually do hit something. does lots of damage. Highly ionising.
- no deflection from electric/magnetic fields
___
STOPPED BY THICK LEAD & CONCRETE
- medical tracers
- radiotherapy
- sterilisation
- detects cracks when inc in radioactivity in GMC
53
geiger muller
- rmb there is a material between radioactive source, and the detector
- -> ensure in lead lined box
- -> use tongs
- -> don't point at anyone
54
contamination
radioactive particles getting onto objects
55
irradiation
exposure to radiation
56
Stellar evolution (up to main sequence)
1. Cloud of dust and gas called a nebula
2. gravitational force pulls the dust and gas together to form a protostar.
- -> Temperature high enough H nuclei undergoes nuclear fusion.
- -> Lots of energy out, keeps star hot. Star is born
3. Enters a long stable period called a main seq. star. Outward pressure due to thermal expansion balances gravitational force.
4. H nuclei in core runs out, gravitational force larger than thermal expansion. Star is compressed. Outer layers extremely hot. Then the Star expands, becomes red giant
57
Stars similar to the sun
- becomes unstable and ejects its outer layer of dust and gas. Only dense solid core- WHITE DWARF.
58
Stars much bigger than our sun
- bigger stars undergo more fusion. Expand and contract several times. They become red supergiants. Eventually they explode in a supernova
- Either: throws outer nebula, becomes neutron star
- Or: if massive enough, collapses into a black hole
