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Physics Mock
Physics Spring Y13
| Question | Answer |
|---|---|
| 'Order' | Opposite of entropy. Order would reduce as temp increases. |
| Terminal velocity | Say at the end why resultant is zero. Also say *drag force*. Say the drag force is increasing at decreasing rate |
| 5cm + 0.5mm on the scale of a graph | Just be careful come on its not 5.5cm |
| Upthrust | Acts upon CoM of fluid displaced. |
| Calculating natural frequency of oscillations | F = -kx = ma a = -xw^2 Hence a = -kx/m = -xw^2 Hence w^2 = k/m w = sqrt(k/m) For given extension, work out force, then a. For that a, use a = -w^2 x to work out the frequency when no driving force |
| Forced oscillation axis titles | Preferably 'driving frequency' not just frequency |
| Damping effect on energy generation | Could argue less is good because more from waves so more available, or could argue more is good because the damping *possibly* transfers the energy |
| When doing 6 marker on amplitude for diff frequencies | Mention measuring frequency - Q doesnt assume you can freely know. Also discuss suitable frequency range i.e. a bit to the left and right of resonant. |
| Rod with unknown CoM from 2 strings, where one has double the force constant. In equilibrium. Find tension in string with the double force constant. | Extension constant so T1 = 2ke and T2 = ke T1 = 2*T2 Equilibrium so T2 + T1 = F 1.5T1 = F, so T1 = 2F/3 Or just think it through for a one marker. |
| Trying to calculate capacitance | Just do it with C = Q/V like come on here. You can get Q from I and t |
| Young's double slits with a white filament lamp | No fringes due to non-coherent source. |
| Calculating speed of sound in air with length of air column in tube and fundamental frequency | We know the shape at f0 so can calc wavelength for wavelength*frequency = speed |
| Scalar or vector: electric field strength | Vector Positive or negative depending on which direction acting |
| Scalar or vector: current | Charge/time Shown by lack of vector addition: diagonal current + horizontal current not weird sum |
| Explain why sound waves can't be plane polarised | Longitudinal, oscillation parallel to energy transfer Define plane polarisation: Polarisation is limiting the oscillations to only one direction which is perpendicular to energy transfer |
| Suggest how experiment making a capacitor and testing its values over time can be accurate and precise | Accuracy is reducing % uncertainty (not strong point) Greater resolution for accuracy e.g. datalogger. Repeat WITH CHANGE to sheets/voltage/area and *average/plot graph* to reduce uncertainty from random error |
| Spreadsheet for capacitor discharge | Not a practical. Instead compare answer to the graph. Calc time constant Split into each column and explain the equations for each, using e.g. B9 + C9 = B10 |
| How to determine count rate for beta | Radiation detector 1m away from source is very wrong. Always measure counts over long period of time |
| Completing graph to show variation of p.d. where it goes along zero at the end to meet back up | Draw the zero section or lose a mark |
| Points for describing particles as waves and evidence | Diffraction/interfere De Broglie = h/p Not localised like particle Electrons, graphite, atomic separate similar to wavelength Changing accel voltage changes wavelength so pattern Rings: construct/destruct Pattern even when very few: each is wave |
| Points for describing waves as particles and evidence | Light photons: quanta of EM e = hf Whole quanta not continuous Photoelectric needs threshold (LED/foil). Discrete frequencies of emission due to discrete energy levels. Intensity below threshold no effect - not continuous transfer like waves |
| Generator calculations | Check if it's a rectangle for the area: don't assume is a circular coil |
| Parallax angle between observations | Halve |
| State why energy passes into the tank (colder) | Not how: why. Say energy from hot to cold |
| 'In terms of particle energies' | Mention KE (mention for both solid and liquid phases), mention PE Mention IE = PE + KE |
| Differences and their meanings between two spectrums (where one has many more lines) | Different intensities of some, and has many more lines showing more elements, so Tau Ceti older as has more time to fuse heavier elements from hydrogen Not necessarily red shifted - these weren't |
| 'Until it crosses Earth's orbit' | When r = 1AU, not when the line stops |
| % uncertainty of emission line | The value on the denom of the equation is the width of the emission line (2.3nm), not the actual wavelength (654nm) |
| Star 50 million light years from earth. Suggest why may contradict Hubble's Law | (should have checked: previous part showed it is blue shifted) Hubble's Law assumes all moving away Blue shifted 'Gravitationally associated' with milky way % uncertainty more than the shift |
| How to show resistance ratio with length and area | R = resistivity*L/A resistivity constant |
| Gravitational potential ratio | /r not /r^2 |
| Faster way of working out % uncertainty for resistors in parallel for *multiple choice question* | Nathan did it by testing the lowest value and using it for the % uncertainty |
| Gas laws | Need to be in Kelvin |
| Finding absolute zero in celcius: finding the y intercept from a graph | When C = 0. It's not a fake y intercept |
| Careful with absorption spectrum multiple choice | Absorption is mostly light |
| How to make sure to place sun on H-R | Less than halfway up, and with arrow heads |
| Limitations of HR | Can't distinguish similar temp stars Need luminosity but not given |
| How temp increasing shifts intensity wavelength graph | Higher by Stefan's, while staying above at all points *peak* wavelength lower, not max |
| Light incident upon tank of water where depth given but not area. Working out total temp change | Use a 1m^2 column. Work out energy incident for the mass there, work out how much that mass will change temp. Will be same temp change for whole tank |
| r and r | Radius vs separation. Don't mess them up |
| Justifying that light is green | 'Middle wavelength' compared to the other ones Among other reasoning |
| How current may affect atmosphere | Electrons ionise electrons in atoms Heating effect |
| Mentioning stationary wave formation on wire in oscillating mag field | Oscillating *force* |
| Explain how electromagnetic induction can charge battery | RATE OF CHANGE OF FLUX LINKAGE causes emf driving current through battery WORK DONE |
| 'Discuss which system would be more appropriate, excluding financial' between gravity storage and thermal | Availability of terrain, scale of production, readiness for transferring energy, storage time possible |
| Part a had you conclude there is a zero error. Part b is a calculation using the graph | Account for the zero error. Write high s.f. in working so they can see you saw the zero error |
| Describing how x-rays produced | Also mention de-exciting in target (k-lines). mention accelerated by high pd before target |
| How gamma rays made | Following alpha or beta. Unstable nuclei. From de-excitation. From annihilation in x-ray production. |
| Gamma vs x rays | Similar energy and penetration X-ray source needs energy, equipment. X-ray can be turned off, can have energy controlled, and doesn't reduce over time like gamma sources |
| Define strain | Extension divided by original length |
| Orbital energy of two objects | The energy from gravity is shared by both aka only counted once. The KE is counted for both based on their speeds. So GPE = 1/2 (sum of both KEs) Then for getting marks mention grav force = centripetal, obviously |
| Why dielectrics good | Electric field polarises it, causing the dielectric to have positive pole and negative pole next to the opposite plates, effectively 'cancelling' some charge, meaning capacitor can store more before electrostatic = emf |
| Charges held on plates by emf | Also held on by the opposite plate |
| P = Fv | Needs resultant zero. F is the magnitude of the resistive/opposite force |
| W = Eq | Work done by power supply = emf * charge |
| Vout = R2/(R1+R2) * Vin | Remember because V kinda proportional to R2. The R1 + R2 is because Vin is based on both resistors Essentially is the resistance of the 'out' divided by the total resistance |
| v = H0 * d | Hubble’s Law |
| C = 4*pi*e*R | For sphere capacitor. This is of free space, as the electric field potential is not defined by its medium |
| W = ½ QV | for capacitors because the charge is increasing over time, so using average charge (aka how it looks when graphed) |
| Function of moderator extra point | Must not absorb |
| Reason why fuel rods stored in water for months | To cool down for processing. Water used to shield from (neutron) radioactivity |
| Water from cooling radioactive materials siphoned away and checked with geiger-muller. What result? | NOT ZERO - BACKGROUND |
| Weird spikes on the binding energy per nucleon graph | Don't sketch them Is of the 4/2 He nucleus and its multiples because it's so stable and so takes more energy to separate (also why alpha is He) |
| Simple explanation for what happens when rate of spinning ball on pendulum increased | One of (frequency, angular velocity, angle to vertical) increases so larger centripetal force Or could spiral into a bunch of factors but not for a two marker |
| Careful with giving value for question answers | Read Q and look at diagram to see exactly what it wants |
| Commenting on relative magnitudes | Mention if negligible |
Created by:
Pyrogearos2