Paper 1 Modelling Flashcards
State the Principle of Moments
Sum of clockwise moments is equal to sum of anti-clockwise moments
Features of geostationary satellite [3]
- Orbit above the equator / equatorial orbit
- Orbit same direction of orbit as Earth’s rotation
- Orbital period is 24 hours
- Orbit is above the same point on the Earth
conditions to be in stationary orbit
has to be equatorial and must move in the same direction as the rotation of the planet
Explain how a specific absorption line is produced in this type of spectrum in terms of
photons and electrons. [3]
Continuous spectrum
• Light / radiation / photons passes through cooler
gas/star’s atmosphere
• Photon(s) absorbed by electron(s)
• Electron(s) excited / jump / make transition to higher
energy level(s)
• Electron only promoted if energy of photon matches
energy gap between two given levels
• Photons remitted in different directions
• (so) idea of contrast with non-absorbed wavelengths
Describe the formation of the sun.
- (Sun/star formed from) dust cloud /nebula / (hydrogen) gas
- Gravitational collapse (AW)
- Temperature of (dust) cloud increases
- Fusion occurs (when the temperature is about 107 K)
- hydrogen nuclei combine to make helium (nuclei)
- Stable size star is produced when thermal / radiation pressure is equal to gravitational pressure
Two properties of a white dwarf
- very hot + low luminosity
- very dense
- mass less than 1.4 solar masses
- no fusion
Features of black hole [2]
- Black hole has higher density/gravitational field
strength/ stronger gravitational field - black hole absorbs light / does not emit visible light
- Has an escape velocity => c
- No fusion in a black hole
- Black hole has smaller mass / radius / size
Define gravitational potential energy of an object at a point in a gravitational field
GPE is the work done in bringing an object from infinity
to a point in the gravitational field
Show that the internal energy of the air in the oven is the same at all temperatures of the
oven. Support your answer with an explanation of the motion of the air molecules in terms of
kinetic theory.
pressure = force/area
* force is caused by air molecules colliding with oven walls
* Newton’s 2nd Law states force = rate of momentum change
* increased temperature means each molecule has greater KE
* hence greater velocity and hence greater momentum
* and more collisions with walls per second
* hence greater rate of momentum change on hitting walls.
* This would lead to greater pressure if N remained constant
* so number of molecules in oven must decrease (air escapes)
* so fewer but ‘harder’ collisions at higher temperatures giving
constant pressure.
* Rms velocity c increases with temperature but number N
decreases and so effects balance out to keep total KE
(½Nmc^2) constant
equate pV = NkT and E =3/2NkT to show E =3/2 pV
* in an ideal gas, all internal energy E is kinetic energy
* so E is independent of temperature
Explain why the horizontal force F between the floor and the tourist is necessary.
(For circular motion) there must (always) be a resultant force
towards the centre
The resultant force is not always vertical/sometimes has a
horizontal component
This can only be provided by friction/cannot be provided by R and W
The collision is perfectly elastic.
State two quantities that are conserved in this type of collision
momentum
kinetic energy / total energy
Describe and explain the motion of the person on the skateboard immediately after the ball
is thrown.
- Motion / speed / force / acceleration of person or
skateboard is in the opposite direction - momentum is conserved / momentum of person =
momentum of ball - total momentum is zero
Describe the motion of the atoms of the metal heater and of the water molecules.[3]
Atoms of metal vibrate (about fixed points)
Water molecules have translational KE
The motion of the water molecules is random
Metal atoms and water molecules have the same KE
Explain what is meant by an inelastic collision.
A collision in which kinetic energy is lost
State Archimedes’ principle.
The upthrust (on an object in a fluid) is equal to the
weight of fluid (it displaces)
Keplar’s first law
The orbit of a planet is an ellipse, with the Sun at one of the two foci
Keplar’s Second law
A line segment joining the Sun to a planet sweeps out equal areas in equal time intervals
Keplar’s third law
The square of the orbital time period T is directly proportional to the cube of the orbital radius r
Define gravitational potential.
Work done per unit mass to move an object from infinity
(to that point)
Describe and explain the next stages of evolution of our Sun.[4]
reduction in energy released by fusion
* gravitational force is greater than that from
radiation and gas pressure
* core collapses
* fusion no longer takes place in the core
* fusion continues in the shell around the core
* outer layers of star expand and cool
* outer layers are released
* reference to planetary nebula
* reference to white dwarf
Explain the role of fuel rods, moderators and control rods in a nuclear reactor
- Fuel rod: Contain the uranium (nuclei) / fissile material
- Control rods: Absorb (some of the) neutrons
- Controls rods prevent uncontrollable chain reactions, so reduce the number of reactions that take place
- Moderator: Slows down the (fast-moving) neutrons
- Slow-moving neutrons have a greater chance of causing
fission / of being absorbed (by U-235)
What is fusion, and the necessary conditions needed to take place in a star
- Fusion is the joining together of nuclei to make ‘heavier’ nuclei
- Mass decreases in the reaction and this is transformed into energy, OR the products have greater binding energy
- High temperatures
- High pressure is required in the core
- The protons/nuclei repel (each other because of their
positive charge) - The strong (nuclear) force comes into play when the
protons/nuclei are close to each other
Describe the evolution of a star much more massive than our Sun
- (When hydrogen / helium runs out) the outer layers of the star expands / a (super) red giant is formed
- The core (of the star) collapses (rapidly) / a supernova is formed
- (Depending on the initial mass of the star the remnant is either a) neutron star or a black hole
Describe the evolution of the universe from the big bang to the present day
Any six from:
1. (At the start, it was) very hot / extremely dense / singularity
2. All forces were unified
3. Expansion led to cooling
4. Quarks / leptons (soup)
5. More matter than antimatter
6. Quarks combine to form hadrons / protons / neutrons
7. Imbalance of neutrons and protons / (primordial) helium produced
8. Atoms formed
9. Idea of gravitational force responsible for formation of stars / galaxies
10. Temperature becomes 2.7 K / 3 K or (the universe is
saturated with cosmic) microwave background radiation
Explain why the energy levels are negative.
- electron must gain to leave the atom
- ionisation level defined as zero
What is meant by isotropic
universe looks the same in all directions
What is meant by homogenous
matter is uniformly distributed
state three assumptions of kinetic model of ideal gases
- particles move with rapid, random motion (WTTE)
- elastic collisions
- negligible (or zero) volume of atoms (compared with volume of container)
- no intermolecular forces (except during collisions)/all internal energy is KE
- collision time negligible (compared to time between collision).
use kinetic theory of gases to explain how a gas exerts a pressure
- molecules make collisions with walls/surface (WTTE)
- (hence) exerts a force on the wall (or each collision has a change of momentum)
- Pressure = force/area
State and explain useful applications of resonance
MUST INCLUDE: The driving frequency matches the natural frequency causing maximum amplitude
Cooking: micro waves cause water molecules to resonate (f = f of em radiation)
Woodwind: reed causes air column to resonate
Brass: lips cause air column to resonate
MRI: radio waves (in a magnetic field) cause nuclei/proton to
resonate
Radios: radio waves cause electrons/current to resonate
Person on swing: intermittent pushes cause swing to
resonate
State and explain nuisance application of resonance
MUST INCLUDE: The driving frequency matches the natural frequency causing maximum amplitude
Bridges: wind/walkers cause the bridge to resonate and increase amplitude of vibration of the bridge
Vehicles: engine vibrations cause panels/mirrors to
resonate / car suspension causes car to vibrate vigourously
Earthquakes: ground vibrating causes buildings to resonate
Define Resonance
- occurs when the frequency of the applied force to an oscillating system is equal to its natural frequency
- the amplitude of the resulting oscillations reaches a maximum
Explain why an object falling vertically through still air reaches a constant velocity.
gravity causes the object to accelerate, initially (1)
resistive forces increase as the object speeds up (1)
resistive forces eventually equals weight of the object(1)
resultant force is now zero (1)
therefore no more acceleration (1)
State Newton’s first law
an object tends to remain in constant motion or stationary unless a resultant force is acted on it
State Newton’s second law
force is proportional to the rate of change of momentum
State Newton’s third law
if object a exerts a force on object b, object b exerts a force of opposite but equal magnitude on to a
Boyle’s law
pressure is inversely proportional to volume for a fixed temperature and mass
Pressure-Temperature law
Pressure is proportional to temperature for a fixed volume
Charles law
Volume is proportional to temperature for a fixed pressure.
Boyles law experiment
Measurements:
Volume with the scale
pressure with a pressure gauge
Experiment:
Take a sealed tube of pressured gas with volume scale. Vary the pressure of the gas and record the volume of the gas
Plot graph of p against 1/v if graph is a straight line through origin then relationship is correct. Gradient is equal to nRT.
Vary pressure slowly so that temperature remains constant.
pressure-temperature law experiment
1) Submerge a round bottom flask of fixed volume in a water bath.
2)Place the water bath on a heater to heat the water.
3) vary the temperature and measure the pressure
Measurements:
pressure with pressure gauge
temperature with thermometer
Plot graph of P against T (degrees celsius)
- draw a line of best fit
- the graph should be a straight line, not through the origin.
- extrapolate to find x-intercept, which should be absolute zero
what happens to the boltzmann distribution when we increase the temperature (normal distribution curve)
At higher temperature the graph is flatter and we see a shift to the right.
state how observations of smoke particles in air lead to conclusions about the nature and properties of molecules of a gas
- movement of smoke particles caused by randomly moving air particles
- smoke particles are continuously moving because air molecules are continuously moving
- smoke particles are visible, but air molecules aren’t thus must be very small
- small movement of smoke particles is due to the large numbers of air molecules hitting from all sides
explain in terms of behaviour of molecules, how a gas exerts a pressure on wall of container
- many molecules collide with walls
- there is a change in momentum
- force is equal to the rate of change of momentum
- pressure = sum of forces/ area of wall
Explain why some helium molecules escape the earth
- helium atoms have a range of speeds
- some helium atoms have a speed higher than the escape velocity
assumptions for kinetic theory of gases
- perfectly elastic collision
- Volume of particles negligible compared to volume of container
- each particle travels in a straight line and has uniform velocity between collisions
- time of collision much smaller than time between collisions
- gas consists of a large number of particles moving randomly
Why is there an increase in temperature when you quickly compress a vessel
molecules collide with piston and rebounds with high speed/momentum
This increases its avg kinetic energy which is proportional to the temperature of system.
How to determine the time period/ frequency in SHM
[spring}
- displace the mass to initiate SHM
- measure 10T from the equilibrium position with the use of a fiducial marker
- Take all measurements from eye level to avoid a parallax error
- Divide your measurements by 10 to get the time period
- Take multiple measurements and then find the mean to improve accuracy
- Calculate frequency using f=1/t
define simple harmonic motion
- acceleration is proportional to the displacement
- acceleration always directed towards the equilibrium
state effects of damping on SHM
amplitude decreases at all points
time period remains constant (amplitude is independent of time period)
peak amplitude occurs at a lower frequemcy
free vs forced oscillation
free - system is disturbed initially but then oscillates with no external force
forced - driving force is applied during oscillation
what is damping
All oscillators experience friction. This frictional force will eventually reduce the amplitude of- the oscillations down to zero.
Investigating if period of oscillations of a simple pendulum is constant for different angles
- Vary the angle and measure the time period
- measure the time period with a stopwatch and angle with protractor
- major difficulty - angle decreases rapidly with each oscillation
- time half an oscillation with a video camera
- Plot graph pf time period against angle
Define internal energy
Sum of the randomly distributed kinetic and potential energy of molecules
Upthrust equation
U=ρgV
upthrust = density * volume displaced * acceleration due to gravity
State and explain a situation where a high SHC is useful
cooling system of a car, where it can absorb large amounts of energy for a small increase in temperature.
state newtons law of gravitation
force is proportional to the product of masses and inversely proportional to the square of the separation
define gravitational field strength
force per unit mass
Describe the pattern of gravitational field lines near surface
- perpendicular to earth’s surface
- parallel to one another
- uniformly spaced
conditions to move in a circular path and why object in orbit is always accelerating
- resultant force perpendicular to the direction of velocity/motion
- velocity is always changing; acceleration acts towards the centre of circle
equation linking orbital speed and radius
v^2=GM/r
state the cosmological principle
Universe is homogenous and isotropic
Huubles law
recessional speed of galaxy is proportional to distance ( fo
converting rpm to rad/s
1rpm=2π/60
red shift of spectral lines
the displacement of a line in the spectrum of a galaxy towards longer wavelengths because the galaxy is receding
Explain what is meant by the big bang and give two suggestions to support the theory
creation of the universe
CMBR ~ 3K
tiny ripples in background temperature
galaxies are moving apart the further away the galaxy the faster the speed of recession
properties of black hole
infinite density
light cannot escape
curves spaces/slows down time
what is fusion and conditions for fusion in star
- fusing together of lighter nuclei to get heavier nuclei
- high temperature so close enough that snf takes effect
- high pressure
- hydreogen nuclei fuse to form helium nuclei
why dont galaxies collapse
galaxies are receding
why is the star brightest at its coolest
Large surface area, therefore it radiates large amounts of energy eg red giant
state whats meant by the big bang and how it explains the origin of microwave background radiation (refer to cosmological principle)
- Creation of the universe
- the universe was hot and infinitely dense
- expansion led to cooling
- current temp is 2.7K due to the radiation present during the big bang
- gamma stretched out to form micorwaves
- CMBR is isotropic
absorption spectrum
when a very hot object emits all the visible wavelengths and then some are absorbed as the light passes through a gas, leaving black lines on the spectrum.
emission spectrum
when an object is heated to lower temperature causing it to emit certain wavelength photons as the electrons de-excite.
wiens law
wavelength emitted with hughest intensity by a black body is inversely proportional to temperature
Stefans law
total radiated power of a star is directly proportional to its temperature to the power of 4
Doppler effect
Objects moving a way from stationary observer will appear to be emitting longer wavelengths than they actually are
