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🅱eet Flashcards

(93 cards)

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1
Q

acceleration=?

A

change in velocity/time

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2
Q

what is the difference between speed and velocity?

A

that velocity is the speed with a direction:

speed is a scalar quantity – it is the magnitude of the velocity. velocity is a vector quantity; it is direction-aware.

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3
Q

momentum=?

A

mass x velocity

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4
Q

force=?

A

mass x acceleration

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5
Q

what is newton’s first law?

A

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

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6
Q

what is inertia?

A

the natural tendency of objects to resist changes in their state of motion, sometimes newtons 1st law is called the law of inertia.

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7
Q

what is conservation of momentum?

A

a fundamental law of physics which states that the momentum of a system is constant if there are no external forces acting on the system. It is embodied in Newton’s first law (the law of inertia).

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8
Q

what is momentum?

A

the quantity of motion of a moving body, measured as a product of its mass and velocity.

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9
Q

what is rate of change of momentum equal to?

A

resultant force

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10
Q

what is the difference between mass and weight?

A

mass-measure of the amount of matter an object is made up of. No matter where you are at given moment in time, mass is constant. measured in g and kg.
weight-a variable and a vector. its direction of pull is towards the centre of the planet. tis measured in Newtons.

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11
Q

what equation links mass and weight?

A

w=mg.
w=weight in newtons
m=mass in kg
g=gravitational field strength in N/kg

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12
Q

what is the gravitational field strength on earth approximated as?

A

10 N/kg

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13
Q

what is newtons third law?

A

For every action, there is an equal and opposite reaction.

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14
Q

what is the law of conservation of energy?

A

the total energy of an isolated system remains constant, energy can neither be created nor destroyed, it can only be transformed or transferred from one form to another.

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15
Q

what are some types of energy?

A 
magnetic
kinetic
thermal
radiant (light)
GPE
sound (energy coming from a vibrating object)
chemical
electrical
elastic potential (stored energy in stretch or squashed objects)
nuclear (stored in the nuclei of atoms)
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16
Q

what is happens to wasted energy?

A

it is transferred to its surroundings and spreads out so much that it becomes difficult to do anything useful with it.

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17
Q

what is useful energy?

A

The portion of final energy which is actually available after final conversion to the consumer for the respective use.

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18
Q

percentage efficiency=?

A

(useful output/total output)x 100

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19
Q

density=?

A

mass/volume

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20
Q

what does a wave do?

A

transfers energy without the net movement of matter.

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21
Q

what are some examples of longitudinal waves?

A

sound waves
ultrasound waves
seismic P-waves

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22
Q

what happens in longitudinal waves?

A

the vibrations are parallel to the direction of wave travel. show areas of compression and rarefaction: compressions are regions of high pressure due to particles being close together,rarefactions are regions of low pressure due to particles being spread further apart.

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23
Q

what are some examples of transverse waves?

A

electromagnetic waves – eg light waves, microwaves, radio waves
seismic S-waves
ripples on the surface of water

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24
Q

what happens in transverse waves?

A

the vibrations are at right angles to the direction of wave travel, peaks and troughs.

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25
what is amplitude?
the maximum extent of a vibration or oscillation, measured from the position of equilibrium.
26
what is wavelength?
the distance between successive crests of a wave.
27
what is frequency?
the number of crests of a wave that move past a given point in a given unit of time. The most common unit of frequency is the hertz (Hz), corresponding to no of crests per second.
28
what is period?
the time needed for one complete cycle of vibration to pass in a given point.
29
what equation links frequency and period?
frequency= 1/period
30
what does 1Hz mean?
1 wave per second
31
wave speed (m/s)=?
frequency (Hz) x wavelength (m)
32
what is the nature and properties of electromagnetic waves?
transverse | travel at the speed of light through a vacuum.
33
what are the uses of ultrasound?
sonar, scanning, animals
34
what are the parts of the spectrum (in order)?
``` radio microwave infrared visible light UV x-rays gamma ```
35
what are the wavelength, frequency, and energy levels like at the gamma part of the spectrum?
shorter wavelength higher frequency higher energy
36
what are the wavelength, frequency, and energy levels like at the radio part of the spectrum?
longer wavelength lower frequency lower energy
37
what is the wavelength of gamma rays ?
< 0.01 nanometers
38
what is the wavelength of radio waves like?
longer than 1 mm.
39
uses of radio waves?
communication such as broadcasting television and radio, communications and satellite transmissions.
40
uses of microwaves?
cooking food, communications and for satellite communications
41
uses of IR?
electrical heaters, cookers for cooking food, short-range communications like remote controls, optical fibres, security systems and thermal imaging cameras.
42
uses of visible light?
photography and illumination,fibre optic communications
43
uses of gamma rays?
sterilising food and medical instruments, and in the treatment and detection of cancer.
44
uses of x rays?
scanning the internal structure of objects and in airport security scanners, internal imaging.
45
uses of uv?
sterilise surgical equipment, sterilise food, produce vitamin D, check bank note forgeries, disinfecting water.
46
dangers of uv?
can cause the skin to burn,can cause damage to skin cells and eyes, and increase the risk of skin cancer and cataracts. ionising radiation.
47
dangers of gamma and x rays?
ionisation can cause the mutation of genes, which can lead to cancer.
48
dangers of microwaves?
Intense sources of microwaves can be dangerous through internal heating of body cells.
49
dangers of IR?
The heating effect of IR can cause burns to the skin.
50
what was thomsons model of the atom?
plum pudding model: atoms are spheres of positive charge electrons are dotted around inside.
51
what was rutherfords model of the atom?
atoms have a central positively charged nucleus where most of the mass is, electron orbit the nucleus-planetary model.
52
what did bohr add to the atomic model?
the fact that electrons occupy energy levels around the nucleus.
53
what is radioactive decay?
the process by which an unstable atomic nucleus loses energy through radiation
54
what are alpha particles?
2 protons and 2 neutrons, same as a helium-2 nucleus.
55
what happens when a nucleus loses an alpha particle?
mass number -4 | atomic number -2
56
what are beta particles?
high speed electrons
57
what happens when a nucleus loses a beta particle?
atomic no +1 | no change to mass number
58
what happens when a nucleus loses gamma?
no change, gamma is only energy
59
what is random nature of radioactive decay?
you can't know precisely when it will next happen, there's no pattern.
60
what is the spontaneous nature of radioactive decay?
it happens on its own. You don't need any external forces to get the isotope to decay.
61
what is the activity of a radioactive sample?
the average number of disintegrations per second.
62
what is the unit of activity of a radioactive sample?
the becquerel (Bq).
63
how do you calculate acitivity of a radioactive sample?
ΔN/ Δt (change in number of undecayed nuclei/change in time in seconds)
64
what is the decay constant?
the probability that a nucleus will decay per second,so its unit is s-1.
65
how do you find activity using the decay constant?
activity = decay constant x the number of undecayed nuclei
66
what is the 🅱enetrating 🅱ower of alpha?
skin/ paper
67
what is the 🅱enetrating 🅱ower of beta?
3 mm aluminium foil
68
what is the 🅱enetrating 🅱ower of gamma?
Lead/concrete
69
how ionising is alpha?
high
70
how ionising is beta?
low
71
how ionising is gamma?
v low
72
what are the sources of background radiation?
Cosmic rays – radiation that reaches the Earth from space Rocks and soil – some rocks are radioactive and give off radioactive radon gas Living things – plants absorb radioactive materials from the soil and these pass up the food chain radioactive waste from nuclear power stations, radioactive fallout from nuclear weapons testing and medical x-rays.
73
what is background radiation?
a measure of the ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.
74
what is half life?
the time it takes for half of the unstable nuclei in a sample to decay or for the activity of the sample to halve or for the count rate to halve.
75
what is nuclear fission?
nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei).
76
what is nuclear fission caused by?
absorption of neutrons
77
what is nuclear fusion?
a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.
78
what are the steps of fusion and what kind of reaction is it?
1H (proton)-2H (deuterium) - 3He - 4He | proton-proton chain
79
why does fusion need such a high temperature?
high temperature gives the hydrogen atoms enough energy to overcome the electrical repulsion between the protons.
80
what are the dangers of using electrostatics?
It is dangerous when there are flammable gases or a high concentration of oxygen. A spark could ignite the gases and cause an explosion. It is dangerous when you touch something with a large electric charge on it. The charge will flow through your body causing an electric shock. This could cause burns or even stop your heart. A person could die from an electric shock.
81
what charge does polythene become?
negative
82
what is the unit for charge?
coulombs (C)
83
what is the charge of 1 electron?`
1.6 x 10^-19 C
84
how do we make it easier to talk about charge?
electron has -1e of charge and proton has 1e of charge where e is 1.6 x 10^-19.
85
current=?
charge/time
86
what is resistance?
ratio of potential difference to current.
87
resistance=?
voltage/current
88
what is power?
energy transferred per second.
89
power=?
current x voltage
90
when does electromagnetic induction occur?
when a wire moves relative to a magnet or when a magnetic field changes.
91
what is a generator?
a coil of wire revolving in a magnetic field.
92
what is work?
the transfer of energy from 1 store to another.
93
what is a field?
an area of space in which a force is felt.

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