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Physics A level > Year 2 - A level > Flashcards

Year 2 - A level Flashcards

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1
Q

What are the two parts of internal energy of molecules?

A
  • Potential energy due to electrostatic attraction

- KE due to movement

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2
Q

Why can’t a body possess heat energy?

A

Heating is energy in transit from hot to cold regions.

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3
Q

Brownian motion

A
  • Jerky, random motion

- Large smoke particles collide randomly with invisible air particles

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4
Q

Diffusion

A

Spread of gas or liquid in space provided.

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5
Q

What is Boyle’s Law?

A

For a fixed mass of gas at constant temp. pressure is inversely proportional to its volume.

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6
Q

Explain kinetic theory and pressure.

A

-Molecules hit container, require force change momentum and rebound.
-Newton 3rd, equal and opposite force on wall.
-Force increases, collisions faster and more frequent. Both increase with speed.
Therfore, KE molecules is directly proportional to temp.

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7
Q

What is Charles’ Law?

A

For a fixed mass of gas at constant pressure, volume is directly proportional to its absolute (kelvin) temperature.

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8
Q

What is the pressure Law?

A

For a fixed mass of gas at constant volume, pressure is directly proportional to Kelvin temperature.

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9
Q

What is the equation with p1 v1 and t1?

A

(P1V1)/T1 = (P2V2)/T2

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10
Q

What unit is temperature measured in?

A

Kelvin 0K = -273 degrees C

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11
Q

What is the ideal gas equation?

A

pV = nRT

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12
Q

KE theory 1.
What is change of momentum of particle m,cx as it hits wall x? What is the time between impacts on wall x over distnace L?

A
  1. Change in momentum = m(-cx) x mcx = -2mcx.

2. t = 2L/cx - between wall x collisions is two lengths

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13
Q

KE theory 2.

What is the force on the particle? and therefore the wall?

A

Change in momentum / time = -mcx^2/L

Newton’s 3rd means wall is +mcx^2/L

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14
Q

KE theory 3.

What is the pressure of 1 molecule?

A

Force / area. mcx^2/L^3 = mcx^2/V

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15
Q

Assuming N molecules what is the equation for pressure?

A

pV = 1/3Nmc^2 - 1/3 move perpendicular to each side.

As Nm is total mass p = 1/3ρc^2

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16
Q

How do you find (root mean squared speed)?

A

Square all speeds, find their mean, square root all

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17
Q

What are the 5 assumptions of ideal gases?

A
  1. No inter particle forces - All KE
  2. All collisions with wall perfectly elastic
  3. Obey Newton’s Laws
  4. Time during collision is negligible
  5. Molecules occupy zero volume
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18
Q

What are the ideal gas eqn’s from theory and expt?

A

Theory: pV =1/3Nmc^2
Expt: pV = nRT
Therefore, RT = 1/3Nmc^2

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19
Q

What is boltzmann’s constant in terms of R and NvA

A

k = Univ. gas constant / avagadro

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20
Q

What is mean KE of a molecule and therfore a mole?

A

KE of molecule = 3KT/2 and of a mole 3RT/2

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21
Q

At given temp what do all molecules have?

A

Same KE.

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22
Q

What links rms speed and temp?

A

Root of temp is proportional to rms speed.

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23
Q

What is a fixed point?

A

A point such as the boiling point of water which can be used to calibrate two thermometers.

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24
Q

Why do objects move in a cirlce?

A

Due to a resultant force acting towards the centre of the circle.

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25
Q

What is the equation for centripetal acceleration?

A

a = v^2/r = rω^2, assuming t and theta are small

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26
Q

What is the equation for centripetal force?

A

F = ma = (mv^2)/r = mrω^2

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27
Q

What is angular velocity? and the equation

A

The velocity of something spinning. ω = v/r = 2π/T = θ/t. rads-1

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28
Q

What is the definition of an electric field?

A

A region where a charged particle will experience a force.

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29
Q

What are the two shapes of electric fields?

A

Point charge - forms radial charge arrows show direction positive charge would move, weaker further from point.
Parallel plates - uniform field, equally spaced lines, equal strength.

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30
Q

What is the equation for electric field strength, force and charge? (uniform)

A

Electric field strength = Force / charge

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31
Q

What is coulomb’s law equation? (radial)

A

Force between = k Qq/r^2

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32
Q

What shows if a force is repulsive or attractive/

A

the symbol. - means attractive, + means repulsive

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33
Q

What are equipotentials?

A

Lines that join points of equal potential. At right angles to the field, indicate how fast a particle might accelerate.

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34
Q

What is the equation linking Electric field strength, voltage and distance? (uniform)

A

Electric field strength = Voltage / distance

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35
Q

What is an equation for electric field strength in radial fields?

A

E.F.S = k Q/ r^2

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36
Q

What is an equation for potential in a radial field? (electric)

A

V = k Q/r

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37
Q

What is a capacitor/

A

Two plates separated by an insulator used to store charge. The amount of charge stored is in capacitance ‘C’ measured in Farads.

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38
Q

What equation links charge, voltage and capacitance?

A

Q = VC

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39
Q

What do capacitors in series have in common?

A

The same amount of charge flows across them all. Therefore, two with different capacitance will have different voltages across them to keep charge the same

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40
Q

What equation links energy stored by a capacitor, voltage and charge?

A

Energy stored = 1/2 VQ.

Can use Q=VC rearranged to replace V or Q.

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41
Q

What is thermionic emission?

A

The release of electrons pfrom metal’s surface due to it being hot.

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42
Q

What equation links potential, work done and charge in uniform electric field/

A

V = W/Q

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43
Q

For discharging capacitors, what equation links charge, initial charge, time, resistance and capacitance?

A

Q = Qo e^-t/RC

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44
Q

For discharging capacitors, what equation links current, initial current, time, resistance and capacitance?

A

I = Io e^-t/RC

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45
Q

For discharging capacitors, what equation links voltage, initial voltage, time, resistance and capacitance?

A

V = Vo e^-t/RC

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46
Q

What is time constant?

A

The resistance x capacitance. The V, I or Q will have fallen to 1/e after 2RC it will be 1/e^2.

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47
Q

After how many time constants are capacitors said to be fully charged or discharged?

A

5RC as 1/e^5 < 1%

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48
Q

What is the definition of gravitational field strength/

A

Force per unit mass. g = F/M

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49
Q

What is the equation for force in gravitational field?

A

F= GMm/r^2

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50
Q

What does G stand for?

A

Universal gravitational constant. 6.672x10^-11 Nm2Kg-2

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51
Q

When is the only time you can use GPE = mgh?

A

In uniform fields close to the Earth surface (few km at most)

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52
Q

What is the equation for grav. field strength using G, mass and radius?

A

g = -GMe/r^2

Negative means attractive force.

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53
Q

What is gravitational potential?

A

The work done moving 1kg from point of 0 potential to a point in the field. Always negative, lowest potential at surface.

54
Q

What is the equation linking grav. potential with G, m and r?

A

V = -GM/r

55
Q

What links potential, WD and mass

A

V = WD/m

56
Q

What links GPE, potential and mass?

A

GPE = Vxm = -GMm/r

57
Q

What does the gradient of a grav. potential against radius graph show?

A

Line is below x axis. Gradient is g.

58
Q

What two equations equal force for objects in orbits/

A

GMm/r^2 = mv^2/r

59
Q

What is escape velocity? and the equation?

A

The velocity needed to escape the Earth’s gravitational field. Change in KE = gain in GPE = WD.
v= √(2Gm/r)

60
Q

What might affect grav. field strength on Earth?

A
  1. Shape. g pole > g equator
  2. Type of rock. More dense = higher g.
  3. Rotation of Earth. Less g at equator as some of g is providing Centripetal acceleration.
61
Q

What are Keplar’s Laws?

A
  1. Orbit of a planet is an ellipse with sun at one focus.
  2. The area of each section is the same time
  3. T^2 is proportional to r^3
62
Q

What links v max, r/A and w

A

Vmax = rw

63
Q

What is the definition of Simple Harmonic Motion?

A

Motion of a body whose acceleration is directed towards a fixed point (equilibrium) and is proportional to distance from that point.

64
Q

What is true of time period?

A

Time period is constant and independent of amplitude.

65
Q

What links accleration, angular velocity and displacment?

A

a = -w^2x

66
Q

What does the graph of acceleration against displacement look like?

A

y = -x graph above and below axis.

67
Q

What does SMH require? and what is the equation

A

A restoring force F = -kx

68
Q

What is time period equation for a pendulum?

A

T = 2π√(L/g) with l as length of string and g as gravity

69
Q

What is time period equation for a mass on a spring

A

T = 2π√(m/k) with k as spring constant and m as mass

70
Q

What equation links angular velocity time and angle/

A

w = θ/t and 2π/T

71
Q

What equation links x, A, w and t?

A

x = Acos(wt)

72
Q

What equation links v, A, w and t?

A

v = -Aw sin(wt)

73
Q

What equation links a, A, w and t?

A

a = -Aw^2 cos(wt)

74
Q

What is total energy?

A

Kinetic energy and GPE continual transfer between these when oscillating

75
Q

What is resonance?

A

Creating maximum amplitude oscillations. When forcing frequency = natural frequency.

76
Q

What is damping?

A

Removing energy(amplitude) from a system. Usually as heat, frequency does not change

77
Q

What does a graph of critical damping look like? and overdamped and lightly damped systems

A

Critical damping - curve returns to equlibrium. 0 on y axis.
Overdamped - Doesn’t return to eq.
Light (Exponential) damping - oscillates and amplitudes form exponential curve.

78
Q

What is the equation linking amplitude, decay constant and time?

A

A = A0 e^-λt

79
Q

Name a natural and artificial damper?

A

Natural - air resistance

Artificial - shock absorber

80
Q

What does a resonance frequency graph look like with and without a graph?

A

Steep curve without damping, flatter wider curve with damping as less energy transfer.

81
Q

Where would we use light or critical damping?

A
  • Light to keep resonance in e.g. Pendulum clock.

- Critical damping to remove resonance e.g. bridges, cars

82
Q

Explain an-echoic chambers.

A

Ductile foam cones can deform a lot before breaking = energy transfer to heat.

83
Q

What size are the atom and nucleus?

A

Atom - 10^-10m

Nucleus - 10^-15m

84
Q

What are atomic mass unit and eV in standard units?

A 
u = 1.66x10^-27 kg
eV = 1.6x10^-19 J
85
Q

What links energy, mass and speed of light?

A

E = mc^2

86
Q

What is binding energy?

A

The energy needed to separate the nucleus into its nucleons.

87
Q

What is the equation for mass defect?

A

Mass defect = mass of nucleons - mass of nucleus

88
Q

What is the most stable element?

A

Iron

89
Q

Why do fission and fusion create more stable elements?

A

Energy is released

90
Q

What is an enegy level?

A

A discrete energy of an electron

91
Q

What is nuclear fusion?

A

Combining two lighter nuclei to get a heavier one and release energy (gamma photons and neutrinos)

92
Q

What does fusion require?

A
  • V high temps

- High densities and pressures (to overcome electrostatic repulsion)

93
Q

What is nuclear fission?

A

Splitting a heavy nucleus into lighter nuclei, releasing energy. (Fire a neutron at it)

94
Q

Name a problem and benefit of fusion and fission.

A

Fusion: Unharmful products, hard conditions, large energy input, releases lots of energy.
Fission: Radioactive products, hard to control(chain reaction), no large energy input, releases lots of energy.

95
Q

What is radioactivity?

A

The spontaneous decay of an unstable nucleus, releasing either alpha or beta particles + gamma photons if spare energy.

96
Q

What are alpha and beta particles?

A

Alpha is helium nucleus (2p, 2n). Beta is high speed electron.

97
Q

What equation links activity, decay constant and number of radio nuclei>

A

dN/dt = -λt

98
Q

What does the decay constant show?

A

The probability that a nuclei will decay per 1 second.

99
Q

What equation links no. nuclei, decay constant and time?

A

N = N0 e^-λt

100
Q

What equation links half life and decay constant?

A

t1/2 = ln2/λ

101
Q

Name two ways to detect radiation?

A
  • Geiger Muller tube

- Photographic plate

102
Q

What is a use for alpha radiation and why?

A

Medical tracers and tracing water leaks. Due to short half life and low ionising.

103
Q

What is a use for gamma radiation?

A

Fuel rods in nuclear reactors. Long half life and highly ionising (heat water to drive turbines)

104
Q

Definition of a black body radiator?

A

One which will absorb all wavelengths of radiation falling on it, at all temperatures.

105
Q

What equation links luminosity, area and temperature?

A 
L = σAT^4
σ = Stephan-Boltzmann's constant
106
Q

What range is the visible spectrum of light?

A

400nm(Violet) - 700nm(Red)

107
Q

What is Wein’s Law? Look at graphs

A

λmaxT = 2.90x10^-3

-In kelvin

108
Q

What are stars?

A

Stars are massive bodies which emit vast amounts of radiant energy from nuclear reactions within.

109
Q

What does observed brightness depend on?

A
  • Size
  • Surface temp.
  • Distance from observer to star
110
Q

What links intensity, luminosity and distance from observer?

A

I = L/4πd^2

111
Q

What is Luminosity and what is intensity?

A 
Luminosity = total power emitted(W)
Intensity = radiant flux = power per unit area(Wm-2)
112
Q

What are two methods of measuring distances to stars?

A

Parallax, Cepheid variable stars

113
Q

How does Parallax method work?

A

Note position of 1st Jan then 1st July. a = r/d as angle is very small.

114
Q

What is a parsec?

A

distance of a star with a parallax angle of a 1 second arc. 3.09x10^16m

115
Q

How does Cepheid variable method work?

A
  • Measure period over which the luminosity varies and you can find the luminosity of Cepheid from graph.
  • Then use I = L/4πd^2 to work out distance.
116
Q

What is a standard candle?

A

A star of known luminosity

117
Q

What is odd about the Hertzsprung-Russell diagram axis?

A
  • Temp. axis goes wrong way from 40,000 to 2500

- Logarithmic scales

118
Q

What equation links wavelength, recessional velocity and speed of light/

A

Δλ/λ = v/c

119
Q

What is redshift?

A

Redshift is due to doppler effect. Galaxies moving away look to have longer λ, so shift to red end of spectrum.

120
Q

Which galaxies show most redshift?

A

Farthest galaxies as highest recessional velocity. Must have highest v as all started at one point(big bang)

121
Q

What links recessional velocity, Hubble constant and distance?

A

V = H0d, 1/H0 = t

122
Q

What would lead to open universe?

A

-Open if av. density < critical value.

123
Q

What would lead to closed universe?

A

If av. density > critical value. GPE will be enough to reverse expansion (big crunch)

124
Q

What would lead to critical universe?

A

If av. density = critical value.

125
Q

Why can we not predict the future of the universe?

A

We can’t detect dark matter, therefore density is unknown. We think with dark matter it is about 1 as gravitational effects on galaxies show.

126
Q

What is the life cycle of a star similar to our sun size?

A

Main sequence –> Red Giant –> White Dwarf –> Black Dwarf.

127
Q

What is the life cycle of a star 3x size of sun?

A

Main sequence –> Super Giants –> Supernova –> Neutron star

128
Q

What is life cycle of a star 10x size of sun?

A

Main sequence –> Super Giant –> Black hole

129
Q

What are two equations for angular velocity to do with angle?

A

= θ/t = 2π/T

130
Q

What is the potential divider equation?

A

Vin = Vout x (R1/R1+R2)

131
Q

What does the overall resistance in parallel circuits depend on?

A

The lowest resistor as that is where the flow would go

Physics A level (3 decks)

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