Paper 2 Flashcards
1
Q
If you hold up an object or lift it at a constant speed, you must be pushing upwards with…
A
A force that’s the same size as the weight
2
Q
Hookes law
A
Force and extension are directly proportional
3
Q
Hookes law practical
A
- Add varying masses on a spring to change force
- Measure extension with a ruler at each weight, plot F against E, and to avoid systematic error measure from the first coil rather than the top of the spring
- Find spring constant from the gradient of the graph
4
Q
Principal of moments
A
A system is at equilibrium when the sum of clockwise moments = the sum of anticlockwise moments
5
Q
Gears can be used to increase moments by
A
Driving a larger gear with a smaller gear
6
Q
Pressure underwater is due to
A
The weight of the column of water above an object pushing down on it
7
Q
Pressure in a gas is due to
A
Particles colliding with a surface, exerting a force
8
Q
To increase pressure in a gas
A
- decrease volume
- add more gas
- increase temperature
9
Q
Why is there a lower pressure at a higher altitude?
A
Less dense atmosphere
10
Q
Typical walking speed
A
1.5m/s
11
Q
Typical running speed
A
3m/s
12
Q
Typical cycling speed
A
6m/s
13
Q
Gradient of a distance/time graph
A
Velocity
14
Q
Gradient of a velocity/time graph
A
Acceleration
15
Q
Area under a velocity/time graph
A
Distance
16
Q
Newton’s 1st
A
If no resultant force acts on an object, it’s motion is constant
17
Q
Newton’s 2nd
A
Force = mass x acceleration
18
Q
Newton’s 3rd
A
For every action there is an equal and opposite reaction
19
Q
Inertia
A
Tendency for an object to be constant, unless acted on by another force
20
Q
Newton’s 2nd practical
A
- Accelerate trolley with mass on string over pulley
- Use photogates to measure acceleration
- Change force by removing masses and placing them on the trolley (to keep total mass the same)
- Ploy F against a, the gradient = the total mass
21
Q
If person B pushes person A, person A
A
Also pushes a force on person B
22
Q
Name 3 effects on thinking distance
A
Distractions, lack of sleep, alcohol, drugs, speed (proportional)
23
Q
Name 3 effects on braking distance
A
Speed, weather, conditions of brake, road, tires
24
Q
If speed doubles, kinetic energy will
A
Go up 4x as much
25
In a collision what is always conserved?
Momentum
26
Rebound collision
M1U1 + M2U2 = M1V1 + M2V2
27
Coupling collision
M1U1 + M2U2 = MV
28
Anything that travels left has a ___ velocity
Negative
29
Canon balls (idk what it's called)
0 = M1V1 + M2V2
30
Longer the time over which momentum is lost or gained
Lower the force exerted
31
What can be used to increase collision time?
Seat belts, airbags, crumple zones
32
How do airbags, seat belts and crumple zones reduce force?
They increase collision time, so momentum is lost over a larger time, reducing force
33
Waves
Transfer energy without transferring matter
34
Longitudinal waves
Direction of oscillations is parallel to direction of energy transfer
35
Transverse waves
Direction of oscillations is perpendicular to direction of energy transfer
36
Frequency
Number of waves passing a point per second
37
How do sound waves work?
They cause the ear drum to vibrate which sends a signal to the brain
38
A frequency of over 20kHz is...
An ultrasound
39
What's the range of human hearing
20Hz to 20kHz
40
When sound hits a boundary between mediums, some is __ and some is __
Transmitted, reflected
41
Are S waves transverse or longitudinal, and can they pass through a liquid?
Transverse, no
42
Are P waves transverse or longitudinal, and can they pass through a liquid?
Longitudinal, yes
43
Resulting echoes from sound hitting a boundary can be timed to build up an image of something, for example
Something underwater or a baby scan
44
Specular reflection
Light reflecting off a smooth surface, where angle of incidence = angle of reflection
45
Diffuse reflection
Where a rough surface will scatter light
46
T/F? EM waves can travel through a vacuum
TRUE
47
Name a use for radio waves
Phones, TV, wifi
48
Name a use for microwaves
Cooking (absorbed by water)
49
Name a use for infrared radiation
Cooking (absorbed by surface)
50
Name a use for visible light
Vision
51
Name a use for ultraviolet
Sunbeds
52
Name a use for Xrays
Medical scans
53
Name a use for gamma rays
Medical
54
All EM waves are emitted and absorbed by ___, except gamma which is emitted by ____
Electrons, nuclei
55
Which EM waves are an example of ionising radiation?
Ultraviolet, Xrays, Gamma
56
As you go from radio-- gamma, what changes?
- shorter wavelengths
- higher frequencies
- more energy
57
Rp- showing matte black to be best absorber and emitter of IR
- Leslie cube with IR thermometer or tubes wrapped in different materials under IR lamp
- shiny materials are worst emitters/absorbers
58
If speed decreases, how are wavelength and frequency effected?
Wavelength decreases
Frequency remains the same
59
Refraction
When a wave enters a new medium, so it's speed changes, causing it to change direction
60
If a wave slows down, it bends___ the normal, causing the angle of refraction to be ___ than the angle of incidence
Towards, smaller
61
Principle focus
Where the lens makes rays cross over
62
Focal lengthv
Distance from centre of lens to principal focus
63
To see where an image is formed, draw two rays from top of object
1. Straight through the centre
2. Parallel then through principal focus
64
Images are either
Real or virtual
Diminished or magnified
Inverted or upright
65
We perceive different colours when
Different wavelengths of light are absorbed by the retina
66
Why will objects appear certain colours
They reflect some wavelengths and absorb others
67
Blackbody
Theoretical object that perfectly absorbs and emits all wavelengths of radiation
68
If rate of absorption is greater than the rate of emission, how is temperature effected?
Increases, however this then increases rate of emission
69
Permanent magnets
Always produce a magnetic field
70
Induced magent
Become magnetised when in another magnetic field
71
What direction to field lines go
North to south
72
Which metals are magnetic
Steel iron cobalt nickel
73
A current carrying wire produces its own
Magnetic field
74
Motor effect
A current carrying wire in a magnetic field will experience a force
75
If a wire is parallel to magnetic field lines...
It experiences no force
76
Fleming's left hand rule: thumb
Force
77
Fleming's left hand rule: index
Magnetic field
78
Fleming's left hand rule: middle
Current
79
How to motors work using the motor effect?
Both sides of a coil experience a force in opposite directions and it turns
80
To increase speed of a motor
- add more turns to coil
- increase pd/current
- use a stronger magnet
81
What does a split ring commutator do?
Ensures current is reserved every half turn in order to keep the coil spinning
82
What direction does current flow?
Positive to negative
83
How do loudspeakers work?
Using motor effect
- current sent from source, causing coil and speaker cone to vibrate, producing sound waves
84
Generator effect
A wire that's moved through a magnetic field will result in an alternating potential difference being induced
85
In a dynamo, what's used instead of a split ring commutator?
Slip rings
86
To increase output in a generator-
More turns in coil, stronger magnet, turn faster
87
If no slip ring, output is (AC/DC)
AC- graph goes above and below X axis
88
Why does turning a generator faster require energy?
Induced current produces its own opposing field
89
How do microphones work?
Generator effect
Sound waves cause coil to oscillate past magnet, inducing a signal
90
With slip rings, output is (AC/DC)
DC, graph stays above X axis
91
Step UP transformer
- more turns on secondary coil
- voltage increases
- current decreases
92
Step DOWN transformer
- more turns on primary coil
- voltage decreases
- current increases
93
Transformers
Change transmission voltage through the national grid to reduce energy loss as heat due to resistance of cables
94
How does a transformer work?b
- AC input to a primary coil induces alternating magnetic field in soft iron core
- this induces a current in the secondary coil
- the side with the most turns (N) has the greater p.d. (V) -- N and V are directly proportional
95
Order of stars' life cycle (red giant)
Nebula, proto star, main sequence star, red giant, white dwarf, black dwarf
96
Order of stars' life cycle (super red giant)
Nebula, proto star, main sequence star, super red giant, supernova, neutron star//black hole
97
Orbits are circular, so while speed is constant...
Velocity is always changing due to direction changing
98
Centripetal force
Always acts towards the centre of the orbit
99
Elliptical orbit
Gets faster as it gets closer to earth
100
Redshift
a result of the space between the Earth and the galaxies expanding. This expansion has the effect of increasing the wavelength of the light from these galaxies, shifting them towards the red end of the spectrum.
101
Distant galaxies are more redshifted, as they're
Receeding at a greater rate
102
What is redshift used as evidence for?
Big band theory
103
What's CMBR, and how does it provide evidence for the big bang theory?
Cosmic microwave background radiation- microwave radiation is detected from all over space// could be matter cooling from the big bang theory
104
Protostar
Gravity pulls the cloud of dust and gas together, leading to a rise in temperature and pressure
105
Main sequence star
Temperature is high enough for hydrogen fusion to begin and the star lights. Forces of gravity and fusion energy are balanced
106
Red giant
Hydrogen fusion stops, the star contracts, heats up and helium fusion begins
107
White dwarf
Stars outer layers drift away, leaving a hot white core
108
Black dwarf
Star cools until it no longer emits light
109
Red super giant
Hydrogen fusion stops, the star contracts, heats up and helium fusion begins. The star continues fusing heavier elements up to iron
110
Supernova
Fusion stops, star collapses under gravity and then explodes. Elements heavier than iron formed
111
Neutron star
Only the core of the star remains, with a density close to that of the atomic nucleus
112
Black hole
Star is sufficiently massive, gravity so large not even light can escape
