Paper 1 Content Flashcards
(235 cards)
1
Q
Base units
A
m ,kg, s, A, K, mol
2
Q
Prefix order (descending)
A
Tera, Giga, Mega, kilo, centi, milli, micro, nano, pico, femto
3
Q
Scalar quantity definition
A
A quantity with magnitude but no direction
4
Q
Scalar quantity examples
A
Mass (kg), speed (ms^-1), p.d. (V), energy (kgm^2s^-2)
5
Q
Vector quantity definition
A
A quantity with both magnitude and direction
6
Q
Vector quantity examples
A
Displacement (m), velocity (ms^-1), force (N), acceleration (ms^-2), momentum (kgms^-1)
7
Q
How to find the direction of a perpendicular vector
A
Find the angle between the between the horizontal and diagonal line using trig^-1
8
Q
What does the gradient of a distance-time graph represent
A
Speed
9
Q
Instantaneous speed definition and how to find it on a graph
A
The speed of a car over a very short time interval. Found by drawing a tangent at one point on a distance-time graph.
10
Q
How do you find the velocity from a distance time graph
A
The gradient of the graph section. Using a tangent if it is a curved section
11
Q
How to find acceleration and displacement from a velocity-time graph
A
The gradient of a v-t graph is acceleration, using a tangent at a point if curved. Displacement can be found by finding the area under the graph.
12
Q
what will a velocity time graph look like with different acceleration types
A
The graph will be a straight, diagonal, line for constant acceleration or deceleration, a flat line for no acceleration and a curve for changing acceleration.
13
Q
Stopping distance definition
A
Thinking distance + braking distance
14
Q
Thinking distance definition
A
The distance traveled between when it’s first noticed that there’s a reason to stop and when they start braking.
15
Q
Braking distance definition
A
The distance travelled from when the brake is first applied until the vehicle fully stops
16
Q
How to find thinking distance
A
Speed of the vehicle x reaction time
17
Q
Experiment to find gravity
A
-hold a ball at a measured height above the ground using a clamp
-place two light gates below this with a measured distance between them
-release the ball from the clamp
-it will interrupt the light gates as it falls starting the timer at the first and ending it at the second
-plot a graph of distance against time^2 and find the gradient and x2 as s=1/2gt^2
18
Q
In projectile motion what is the general acceleration horizontally or vertically? What does this mean for the velocity?
A
Horizontal acceleration: 0
Vertical acceleration: 9.81 or -9.81
Horizontal velocity (u and v): remains constant
Vertical velocity (u and v): changes
19
Q
difference between energy and work done
A
Work is the transfer of energy when a force moves something. energy is the capacity to do work. (movement is required for work to be done)
20
Q
How to find the weight of an object in a lab
A
Using a newtonmeter or w=mg
21
Q
What is a centre of mass
A
A point on an object through which an external force produces motion but no rotation. It is a point where the entire weight of the object appears to act.
22
Q
How to find the centre of mass/gravity in a lab
A
It can be found as it is vertical below the point of suspension when the object if lifted. Create holes around the objects edge and hang it, draw vertical lines downwards from this point and repeat for other holes. Where the lines cross is the centre of mass
23
Q
How to find normal contact force of an object on a slope
A
-weight acts vertically downwards
-mgcos(x) can be used to find the force opposing the normal contact force (x is the angle between the slope and the horizontal)
-this is equal to the normal contact force
24
Q
What is drag
A
The frictional force acting on an object that opposes the motion of the object
25
Terminal velocity definition
When the drag of an object in motion is equal to the weight of the object. Acceleration is 0.
26
How does terminal velocity occur
-the object initially releases with no air resistance and is only acted on by weight. acceleration=9.81
-The drag of the falling object increases as the speed increases.
-The resultant force decreases.
-instantaneous acceleration becomes less than gravity
-The resultant force becomes 0 and acceleration now=0
27
How to show terminal velocity in a lab
-measure and record the mass (using a digital balance) and diameter (at 3 different places) of a metal ball
-drop the ball in a measuring cylinder full of a viscous liquid
-measure the time taken for the ball to sink to the bottom
-divide this time by 6 and drop the ball again marking where it reaches every 1/6 of the time it took to sink with a pen
-measure the displacements between each of these points with a ruler
-draw a displacement-time graph and see if it looks like it’s reached terminal velocity
28
Definition of a moment
The force on an object multiplied by the perpendicular distance of this force from the pivot
29
Principle of moments
For an object in rotational equilibrium, the sum of the clockwise moment = sum of the anticlockwise moment.
30
Torque definition for a couple
One of the forces in the couple multiplied by the perpendicular distance between the forces
31
Forces in equilibrium meaning
Net force and net moment acting on the object are both 0
32
How to show forces in equilibrium
A closed triangle with arrows going head to tail in a loop.
33
Density definition
The mass per unit volume of a substance
34
How to find density of a liquid in a lab
For liquids: find the volume from a measuring cylinder and mass from a digital balance
35
How to find density of an irregular solid in a lab
The volume can be found using the displacement of a liquid after putting the solid in it. It is the difference between the water levels before and after it is dropped in it using a measuring cylinder. Measure mass on a digital balance.
36
How to find the density of a regular solid in a lab
measure all three dimensions of the object using a ruler calliper or micrometer and multiply them for volume. Use a digital balance for the mass
37
What is special about pressure in a fluid
It acts in all directions
38
What is archimedes principle
The upthrust on a body in a fluid is equal to the weight of the fluid the body displaces
39
Why do some objects in a fluid float?
Their weight must be equal to the weight of the fluid displaced.
40
Light object such as wood is submerged in water. What happens?
-upthrust and weight immediately act on the object
-upthrust is greater than weight and weight is less than the weight of displaced water causing it to accelerate upward
-it exits at the waters surface
-weight and upthrust are now in equilibrium, less water is displaced
41
Newton’s first law definition
An object at rest or moving with constant velocity will remain that way unless acted on by a resultant force
42
How can you reduce random errors
Repeat the experiment many times
43
How do you find the combined uncertainty quantities being added or subtracted
always ADD the absolute uncertainties
44
How do you find the combined uncertainty quantities being multiplied or divided
Add the percentage uncertainties
45
How do you find the combined uncertainty quantities raised to a power
Multiply the percentage uncertainty by the power
46
How do you convert from absolute to percentage uncertainties
To find the percentage uncertainty: divide the absolute uncertainty by the measured value and x100
To find the absolute uncertainty:
Divide the percentage uncertainty by 100 and multiply by the measured value
47
How do you show uncertainties on a graph
Draw error bars at the measured points
48
How do you find the uncertainty using error bars on a graph
Top left to bottom right or top right to bottom left of the error bars draw a line of worst fit. The gradient of this is used to show the maximum possible error in the gradient of the data.
49
Newton’s third law definition
When two objects interact, they exert equal and opposite forces on eachother
50
What are the conditions for Newton’s third law to apply
-the forces must be of the same type
-they must act on two different objects
51
What is the resultant force on an object travelling at a constant velocity
0N
52
conservation of energy definition
the total energy in a closed system remains constant as energy cannot be created or destroyed but can only be transferred.
53
internal energy definition
the sum of the random kinetic energy and the random potential energy of atoms in a system
54
elastic deformation definition
a reversible change in the shape of an object due to a compressive or tensile force. when the force is removed it will return to its original shape
55
plastic deformation
an irreversible change to the shape of an object due to tensile or compressive forces. when the force is removed it will not return to its original shape.
56
hookes law
the extension on a spring is directly proportional to the force applied to it provided the limit of proportionality has not been exeeded.
57
how to show hookes law in a lab
-attach a spring to the end of a clamp suspended on a stand above a bench
-place a metre rule next to the spring
-add masses to the spring and check the extension for each mass added
-wear goggles and have it at eye level to reduce parallax error
-repeat experiment 3+ times
-plot F (mass x 9.81) against extension on graph
-hookes law is shown if line of best fit is proportional through 0
58
limit of proportionality definition
the force beyond which stress is directly proportional to strain
59
elastic limit definition
the force beyond which the material will no longer return to its original shape and will deform plastically.
60
what is the area under a force-extension graph equal to
work done
61
what happens to work done in plastic vs elastic deformation
elastic: the elastic potential energy is fully recoverable
plastic: energy has gone into moving atoms into new permanent positions so this part is not recoverable
62
what does a force-extension graph look like for a spring. draw it
look it up
63
what does a force-extension graph look like for rubber bands. draw it
look it up.
64
what does a force-extension graph look like for polythene strips. draw it
look it up
65
what is the area inside the hysteresis loop of a rubber force-extension graph equal to
the thermal energy released when the rubber is loaded and unloaded
66
what are yield points on a stress-strain graph
where the material extends rapidly
67
what does a stress-strain graph look like for a brittle material. draw it
a directly proportional line which does not curve at the top but abruptly stops (when it snaps)
68
what is the ultimate tensile strength of a material and what happens after this
the maximum stress a meterial can be stretched before it breaks after which it will become longer and thinner and snaps at its breaking point.
69
draw a stress-strain graph for a metal (ductile) and label: the limit of proportionality, elastic limit, yield points, ultimate tensile strength and breaking point
look it up
70
how to find young modulus on a stress-strain graph
the gradient of the linear region
71
stiffness definition
the ability of an object to resist deformation
72
how to compare the stiffness of objects
compare the young modulus. bigger young modulus=stiffer
73
how to find young modulus in a lab
-measure the initial length of a metal wire with a meter ruler and its diameter using a micrometer at at least 3 different points along it to find an average
-use this to find its cross sectional area
-clamp the wire to one side of a bench and put the other side over a pulley at the opposite end with a marked point on the wire above a ruler and note this point
-place known masses at the end of the wire
-each time analyse the distance the marked point has moved (extension)
-calculate the stress and strain of the wire
-plot a stress-strain graph and find the gradient of the straight part for the young modulus
74
draw a stress-strain graph of a polymer
look it up
75
what is the law of conservation of momentum
total momentum of a system remains the same before and after a collision provided no external forces act on the system
76
what happens when two objects collide
-some momentum is transferred from one object to the other
-some kinetic energy is transferred from one object to the other
-total momentum does not change
77
what is a closed system
an isolated system which has no interaction with outside influences or forces.
78
how to show momentum of a collision in a lab
-place a meter ruler next to a linear track
-find the masses of two trolleys with a digital balance
-place two trolleys (with magnets facing eachother if inelastic)on the linear track. one at 0m and one at 0.5m
-push one trolley so that it collides with the second
-time how long it takes to reach the second trolley at 0.5m and then how long it takes for the combined trolleys to reach 1m
-use this to find the velocity before and after the collision
-repeat for means
-use p=mv to find momentum before and after
79
what is conserved in a perfectly elastic collision
everything is conserved:
-momentum
-total energy
-total kinetic energy
80
what is/isn't conserved in an inelastic collision
-momentum
-total energy
-not total kinetic energy
81
newtons second law definition
the resultant force acting on an object is directly proportional to the rate of change of momentum and acts in the same direction
82
when can F=ma be used instead of newtons 2nd law
when the mass of the object is constant
83
impulse definition and equation
the product of the force and the time for which the force acts. Force x Δtime =Δmomentum
84
how do you find the impulse from a force-time graph
the area underneath it
85
how to resolve momentum
initial momentum in x direction=final momentum in x direction
initial momentum in y direction=final momentum in y direction
resolve the same way as any other vector
86
What are the conditions for an object to be in equilibrium
-resultant force must =0
-resultant moment must =0
87
What error is caused by looking at an experiment from the wrong angle? How to solve this?
Parallax error. Have the experiment at eye level
88
What is the triple point of a substance
A temperature and pressure where the three phases of matter can exist in thermal equilibrium.
89
Thermal equilibrium definition
When two objects have no net flow of thermal energy between them.
90
What does it mean for two objects to be in thermal equilibrium
They must be the same temperature
91
What is a zero-error
When measuring something, the equipment shows a non-zero reading when in reality it should be zero
92
Precision vs accuracy
Accuracy: how close a measurement is to its true, accepted value
Precision: how close a set of measurements are to eachother
93
How convert from Celsius to kelvin
+273 to the Celsius number it will always be a positive number in kelvin
94
Absolute zero definition
The lowest possible temperature at which the substance has minimal internal energy
95
When to use degrees vs when to use kelvin
always use kelvin when temp is shown as T. use either degrees or kelvin for θ (based on whats given in the question)
96
what is the structure of solids in terms of spacing, ordering and motion of atoms
-arranged in a uniform structure with strong electrostatic of attraction between atoms
-fixed position but can vibrate (more vibration if heated) and therefore have kinetic energy
-atoms are close together
97
what is the structure of liquids in terms of spacing, ordering and motion of atoms
-particles are free to move non-uniformly around eachother without a fixed shape
-more kinetic energy than solids
-still electrostatic forces between the atoms so still close together
98
what is the structure of gases in terms of spacing, ordering and motion of atoms
-atoms are far apart as there is almost no attraction
-move freely and non uniformly at high speeds
-no fixed shape
99
what is it called when a solid changes state to a liquid
melting
100
what is it called when a liquid changes state to a gas
boiling/evaporation
101
what is it called when a gas changes state to a liquid
condensation
102
what is it called when a liquid changes state to a solid
freezing
103
what is the kinetic model
all matter is made of tiny particles constantly moving.
104
what is Brownian motion
the continuous random motion of particles in a fluid (liquid or gas)
105
how is brownian motion shown in a lab
-fill a smoke cell with smoke particles by burning paper
-seal the cell to stop these particles escaping
-shine a bright light through the smoke cell after turning off main lights
-look through a microscope at the centre of the smoke cell
-tiny bright dots (smoke cells) will be seen jittering randomly
-this is because of their collisions with tiny air particles
106
what happens when the temperature of a substance is increased in terms of internal energy, KE and PE
-internal energy increases
-average kinetic energy of the atoms increases
-potential energy of the atoms remain the same
107
what happens when a substance changes phase in terms of temp, internal energy, KE and PE
-temp doesn't change
-kinetic energy doesn't change
-potential energy significantly increases
-internal energy increases
108
draw a graph for a solid being heated up until it becomes a gas and label where: KE changes, PE changes, the states of matter, the processes of the changes of state, the axis, internal energy
-temp on y-axis time on x-axis
-directly proportional line from 0 for solid where KE and temp increases but PE remains the same
-flat section where PE increases but temp and KE are the same (melting->, freezing<-)
-proportional line for liquid where KE and temp increases but PE remains the same
-flat section where PE increases but temp and KE are the same (boiling->, condensation <-)
-proportional line for gas where KE and temp increases but PE remains the same
-internal energy increases throughout
109
specific heat capacity definition
the energy required to change the temperature of 1kg of a substance by 1K
110
how to find the specific heat capacity of a solid in a lab
-find the mass of a solid using a digital balance with holes for a thermometer and electric heater
-place the solid in an insulating substance
-measure the current and p.d of the heater by connecting it to an ammeter and voltmeter
-set a timer for 10 minutes
-check the temp before and after the 10 mins on the thermometer by looking at eye level to reduce parallax error
-c = IVt/mΔθ
111
how to find the specific heat capacity of a liquid in a lab
-find the mass of a liquid using a digital balance
-pour the liquid in an insulating container
-place a thermometer in the liquid and measure the initial temp (at eye level to reduce parallax error)
-place an electric heater connected to a voltmeter and ammeter in the liquid
-time this for 10 mins whilst stirring to uniformly distribute the heat
-after 10 mins find the final temp on the thermometer
-c = IVt/mΔθ
112
what is the method of mixtures and what is needed
a way to find the specific heat capacity of a substance by mixing two substances at different temperatures: requires both known masses, the final temperature (when they are in thermal equilibrium), specific heat capacity of one of the substances.
113
specific latent heat definition
the energy required to change the phase of a substance per 1kg whilst at a constant temperature
114
how do you find the specific latent heat of fusion in a lab
115
how do you find the specific latent heat of vaporisation in a lab
116
what assumptions are made in the kinetic model for an ideal gas
-the atoms occupy a negligible volume compared to the volume of the gas
-atoms in the gas move in random directions at random speeds
-the collisions of particles with eachother and the container walls are perfectly elastic
-the time of collisions between atoms is negligible compared to collisions with the walls
117
how does the kinetic model of an ideal gas show newtons laws
-when atoms collide with the container wall, they exert a force on the wall which exerts an equal and opposite force on them (3rd law)
-this changes their momentum as they bounce off as a force is exerted over a short length of time (2nd law)
-this changes the atoms direction making its velocity change from 2mu to -2mu
-the atom travels to and collides with the other wall and repeats this
-as the atom collides with the wall, it causes pressure on the wall as P=F/A
118
Boyles law definition
the pressure of an ideal gas is inversely proportional to its volume provided that the mass of the gas and its temperature do not vary
P∝ 1/V
119
experiment to show boyles law in a lab
120
Charles law definition
for a constant pressure, the volume of a gas is directly proportional to the temperature.
V∝T
121
what is the relationship between pressure and temperature. what are the conditions for this?
provided that the volume and mass of the gas remains constant, pressure is directly proportional to temperature.
p∝T
122
what is absolute zero in kelvin
0K
123
what is absolute zero in celcius
-273°C
124
how do you estimate absolute zero in a lab
-place a water bath on a an electric heater and a thermometer in the water
-fill a flask with dry air, seal it and attach a pressure gauge
-watch the thermometer and pressure gauge as the water is heated at eye level to reduce parallax error
-plot a graph of temp against pressure and extrapolate to find absolute 0
125
draw and label a maxwell-boltzmann distribution. where is the most probable speed, mean speed, root mean square speed, axis and temperature of 2 curves
look it up
126
how do you convert from degrees to radians
angle in degrees x π/180
127
how to calculate root mean square speed
square each speed and add each speed, ignoring any negative signs (as it is a scalar) then divide by the number of of numbers. then root this
128
angular velocity definition
the rate of change of the angle per unit of time for an object moving in a circular path
129
what is the angle measured in for circular motion and oscillations
radians
130
centripetal force definition
a force which acts towards the centre of a circular path and is perpendicular to the direction of the objects displacement making it move in a curved path
131
how would someone feel at the top of a loop while in circular motion
light or weightless
132
where does the resultant force act towards for someone at the top of a loop whilst in circular motion
it acts towards the centre. this is the centripetal force
133
how is angular and linear velocity related
at any point on a circular path the linear velocity is at a tangent to the curve.
134
centripetal acceleration definition
the acceleration of an object travelling in a circular path at a constant speed (varying velocity)
135
experiment for circular motion in a lab
-attach known masses to the bottom of a string and a lighter mass (bung) at the opposite end of the tube+string
-thread this through a glass tube
-spin the glass tube horizontally, the bottom weight will remain stationary if mg=the centripetal force
-calculate the radius of the circular motion of the bung
-use equations to find the weight and therefore the centripetal force
136
what types of forces could be centripetal
gravitational force, tension, friction
137
what does greater speeds mean for the amount of centripetal force needed
more is needed to maintain the circular path
138
at the top of a wheel what is the relationship between weight and normal contact force? how to find net force?
normal contact force (N) is bigger than the weight(mg). net force= mg-N
139
displacement definition (oscillations)
the distance from the equilibrium position
140
frequency definition (oscillations)
the number of complete oscillations per unit time
141
period definition (oscillations)
the time taken for one full oscillation
142
amplitude definition (oscillations)
the maximum displacement from the equilibrium position
143
what unit is used to measure angles in circular motion
radians
144
how to convert joules (J) to electronvolts (eV)
divide joules by 1.6x10^-19
145
how to convert electronvolts (eV) to joules (J)
multiply eV by 1.6x10^-19
146
for 2 pendulums in antiphase, what will their displacements be at the same time
one will be at its maximum positive displacement whilst the other will be at its maximum negative displacement
147
for 2 pendulums in phase, what will their displacements be at the same time
they will both be at their maximum positive displacement
148
simple harmonic motion definition
oscillating motion where and objects acceleration is directly proportional to its displacement and acts in the opposite direction
149
what are the 2 key features for objects in simple harmonic motion
-its acceleration is directly proportional to its displacement
-the acceleration acts in the opposite direction to the displacement
150
what is the gradient of a acceleration-displacementt graph for simple harmonic motion
-angular velocity squared
151
how are the period (T) and amplitude (A) related in simple harmonic motion
they are independent of eachother/not related
152
in SHM what happens to the frequency of period of oscillation
they remain constant provided there is no energy lost from the system
153
what is an isochronous oscillator
an oscillator that takes the same amount of time for one oscillation regardless of the amplitude
154
experiment to show simple harmonic motion
-suspend a thread attached to a ball (weight) from a fixed point with a stand and clamp
-place a fiducial marker below the balls centre whilst it is at rest. this is the equilibrium position
-pull the ball to the side of the equilibrium position, measure this distance with a ruler and release it, starting a stopwatch at the same time
-count 50 oscillations with each one being when the ball passes the equilibrium position before stopping the timer
-repeat this, wear goggles and crouch to eye level to reduce parallax error
-plot a graph of results
155
what energy change is important for SHM
kinetic and potential energy stores (especially gravitational or elastic) transfer between eachother lots
156
for SHM what happens to total energy
it remains constant as there are no frictional forces (sum of PE and KE remains the same)
157
draw an energy-displacement graph for an object in SHM
look it up (pg 60 book 2)
158
damping definition
the reduction of the amplitude of oscillations when an external force acts on the oscillator
159
draw a graph of an oscillation undergoing light damping, heavy damping and very heavy damping
look it up (pg 63 book 2)
160
free oscillation definition
the motion of a system displaced from its equilibrium position, allowed to operate without any external forces
161
forced oscillation definition
an oscillation in which a periodic driver force is applied to an oscillator
162
driving frequency definition
the frequency at which the periodic driver force is applied to a system in forced operation
163
resonance definition
the increase in amplitude of an oscillation when the driving frequency matches the natural frequency of the system
164
natural frequency definition
the frequency of a free oscillation
165
what are 2 examples of forced oscillations
-a vibration generator attached to a string
-a hand lifting a spring up and down at a consistent rate
166
for a bridge, what could cause resonance and why?
the driving frequency of the wind is equal to the natural frequency of the bridge which causes a dramatic increase in amplitude making it oscillate/wobble and collapse
167
how do you prevent the effects of resonance
damping. it reduces the amplitude from its amplitude during resonance
168
gravitational field definition
an infinite field created around any object with mass which diminishes as distance from the centre of mass increases
169
gravitational field lines definition
lines of force used to map the gravitational field pattern around an object with mass
170
gravitational field strength definition
the gravitational force exerted per unit mass on a small object
171
draw the radial field lines around a sphere such as a planet or point mass
all pointed to the centre of mass at equal distances
172
how do gravitational field lines act near the earths surface? draw it
uniformly, acting downwards towards the equator. look it up (book 2 pg73)
173
what is newtons law of gravitation
the force between two point masses is directly proportional to the product of the masses and inverse to the square of the separation between them #
174
what type of quantity is gravity? how do you therefore combine them
a vector. addition and subtraction
175
what is keplars first law
the orbit of a planet is an ellipse with the sun at the centre of the two foci
176
how are most orbits of planets modelled. why
as a circle as their orbits have low eccentricity
177
what is keplars second law
a line segment joining a planet and the sun sweeps out equal areas during equal intervals of time
178
what is keplars third law
the square of the orbital period of a planet is directly proportional to the cube of its average distance from the sun
179
what does keplars laws apply to
any object in orbit around a larger object eg. the earth round the sun or a satellite round the earth
180
satellite definition
a body orbitting around a planet
181
geostationary satellite definition
a satellite that remains in the same position relative to a spot on the earths surface
182
what are the conditions for a satellite to be geostationary
-must be in orbit above the earths equator
-must rotate in the same direction as earth
-must have an orbital period of 24 hours
183
escape velocity definition
the minimum velocity at which an object has just enough energy to leave a gravitational field
184
what effect does the mass of an object have on its escape velocity
no effect. it is the same for all objects regardless of mass
185
aphelion definition
the furthest point from the sun in an elliptical orbit
186
big bang definition
the theory that at a moment in the past all matter in the universe was contained in a single point from which the universe rapidly expanded outwards
187
black hole definition
the remnant core of a massive star after its collapse with an escape velocity greater than the speed of light
188
blue shift definition
the shortening of an observed wavelength when a wave source moves towards the observer
189
chain reaction definition
a reaction in which the nuetrons from a fission stage are responsible for further fission causing exponential growth in reaction rate
190
chandraskar limit definition
the mass of a stars core beneath which the electron degeneracy pressure is sufficient to prevent gravitational collapse. limit is 1.44 solar masses
191
comet definition
a small, irregular body of mass made of ice, dust and rock which orbit the sun with high eccentricity
192
cosmological principle definition
the assumption that, the universe is homogeneous and isotropic and the laws of physics are universal
193
dark energy definition
a hypothetical form of energy that fills all of space and would explain the expanding universe
194
dark matter definition
a hypothetical form of matter that neither emits or absorbs light that could explain the difference between the predicted and observed velocities of stars
195
how do objects orbit stars and planets
in an ellipse with eccentricity depending on both masses
196
electron degeneracy pressure definition
a pressure created by electrons in the core of a collapsing star due to the Pauli exclusion principle
197
what is the chandraskar limit
1.44 solar masses
198
emission line spectrum definition
a set of specific frequencys of EM radiation visible as bright and dark lines as electrons transition between energy levels
199
expanding universe definition
the idea that space and time is expanding and the further the points are apart, the faster they move away from each other
200
fission definition
a process in which a nucleus splits into two smaller nuclei after absorbing a neutron
201
fusion definition
a process in which two smaller nuclei join to form one larger nucleus
202
galaxy definition
a collection of stars and interstellar dust bounded by gravitational attraction
203
gas pressure definition
the pressure of the nuclei in a stars core pushing outwards and counteracting the gravitational force
204
homogeneous definition
uniform in terms of the distribution of matter across the universe when viewed on a large scale
205
how to find the hubble constant on a speed-distance graph, what is the condition for this
the gradient. it must be recessional
206
hubbles law definition
the recessional speed of a galaxy is almost directly proportional to its distance from earth
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light year definition
the distance travelled by light in a vacuum in one year
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luminosity definition
the total radiant power output of a star
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main sequence definition
the main period of a stars life during which its stable
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parallax angle definition
the angle of the apparent shift in the position of nearby stars against a background of far away stars due to the earth orbitting the sun
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parsec definition
the distance at which a radius of 1AU subtends an angle of one arcsecond
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perihelion definition
the closest point in an orbit to the sun
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planetary nebula definition
the outer layers of a red giant that have drifted into space leaving the hot core as a white dwarf
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protostar definition
a very hot very dense sphere of condensing dust and gas prior to becoming a star (no fusion)
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red supergiant and giant definition
an expanding star at the end of its life which no longer fuses elements in its core but does in its outer with lighter elements (supergiant for large stars)
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red shift definition
the lengthening of observed wavelength that occurs when a wave source is moving away
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spectral line definition
a line in an emission or absorption spectrum at a specific wavelength
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spectroposy definition
a technique used to identify spectral lines to identify elements in stars
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supernova definition
the implosion of a red supergiant at the end of its life which leads to ejection of stellar matter into space leaving a remnant core
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universe definition
everything that exists within space and time
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white dwarf definition
a very dense star formed from the core of a red giant in which no fusion occurs
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wiens law
the maximum wavelength at which intensity of radiation is at its maximum from a black body is inversely proportional to the absolute temp of the body
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nebula definition
a cloud of dust and gas hundreds of times larger than our solar system
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formation of a main sequence star
-nabulae are formed by gravity pulling dust and gas towards eachother forming clouds
-this becomes increasingly hot and dense as the dust gets closer together until a protostar is formed within the nebula as a very hot, very dense sphere
-because of the very high temps of the core, the electrostatic repulsion of light elements up to iron is overcome through nuclear fusion which releases energy outwardly (when fusion starts it is a star)
-enters main sequence and expands as the radiation and gas pressure are larger than the gravity until they are in equilibrium (main sequence)
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life cycle of a normal mass star after main sequence
-when the hydrogen within the stars core is depleted and it is no longer hot enough to fuse helium nuclei, the shell of the star starts fusion causing expansion as a red giant
-the outer layers of the red giant drift into space forming a planetary nebula and leaving the core as a white dwarf at around 30000K due to electron degeneracy pressure caused by electrons being squeezed together
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life cycle of a massive star after main sequence
-because of the extreme heats of the core fusion is still able to happen for helium atoms and overcome the electrostatic forces making heavier atoms up to iron and causing the star to expand into a red supergiant
-the red supergiant implodes when its core is made of iron as there is not enough energy for more fusion ejecting the core materials into space (this is called a supernova)
-the remnant core is compressed either into a black hole or nuetron star (both at above the chandrascar limit of 1.44 solar masses but only a black hole if above 3 solar masses)
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what is the key feature of a black hole
the escape velocity is greater than the speed of light due to the extreme gravitational pull so photons can not escape
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draw a hertzprung-russel diagram labelling the axis, groups of star types (by circling) and the quantities on the axis
look it up (yr 2 pg 103)
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what is the correlation between luminosity and brightness of stars
they are generally proportional
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what are the observations for energy levels of electrons
-an electron cannot have a quantity of energy between two energy levels
-the energy levels are negative because external energy is required to remove them from the atom
-an electron with zero energy is free from the atom
-the most negative energy level is called the ground state
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what is it called when an electron moves up/down an energy level
exited (up), de-exited (down)
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what happens when an electron is de-exited
the electron loses energy but because energy is conserved, a photon is released
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what happens when a photon is absorbed by an electron
the electron temporarily gets exited before getting de-exited again. when it de-exites, it releases a photon of the same wavelength as the initial photon but in a random direction around the sphere
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how do you detect the elements within stars
if we know the line spectrum of a particular element, the spectral lines will appear as dark lines in the absorption line spectrum
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