Wrong Exam Questions Flashcards
A student uses the relationship f is proportional to sqrt T to predict much higher frequencies than the one in the experiment
Explain how the actual frequencies produced would be different from those that the student predicts
[2 marks]
f is proportional to sqrt T when l and mu are constant [f= 1/2l sqrt(T/mu)]
when tension is increased too much, the string will stretch out and hence have a smaller diameter hence there will be a lower mass per unit length so frequency higher.
Discuss the energy transfers that take place when a vehicle is decelerated in a gravel escape lane.
[2 marks]
The kinetic energy of the lorry is transferred to the kinetic energy of the gravel as it is moved.
Transfer to thermal energy as the gravel is heated up.
IGNORE REFERENCES TO FRICTION
Discuss whether an escape lane containing gravel or an escape ramp would provide the safer experience for the driver of the vehicle as it comes to rest.
[1 mark]
Ramp because:
-uniform deceleration
-travelling through gravel might make the vehicle unstable
Gravel because:
-if the brakes have failed, the lorry would roll backwards after stopping
Explain how the pattern produced on the screen of an an electron diffraction tube supports the idea that the electron beam is behaving as a wave rather than a stream of particles.
[3 marks]
Particle behaviour wouldn’t produce a patter, as they would scatter randomly.
Wave property is shown by diffraction and interference. Graphite causes electron beam to spread out. Bright rings occur where waves interfere constructively. Maxima when sin theta=n lambda/d .
Essentially marks for:
-explaining appearance of screen if particles
-identifying wave property
-explaining what happens when diffraction occurs
-explaining cause of bright rings
-similar to diffraction grating formula
Explain how the emission of light from the fluorescent screen shows that the electrons incident on it are behaving as particles.
[3 marks]
The energy transfer is a 1 to 1 interaction, hence, the electrons must instantly provide enough kinetic energy to cause excitation.
When electrons collide, electrons within the atoms move into higher energy levels.
The light emission is due to photons emitted when atoms de-excite.
Mention of photoelectric effect= no marks awarded
Explain how stationary wave is produced when a stretched string is plucked.
[3 marks]
-Waves travel to the boundaries and are reflected,
-two coherent waves travelling in opposite directions superpose.
-Nodes are created at fix ends as they cannot move, therefore, destructive interference occurs there.
State and explain the effect on the output pd when temperature of the thermistor is increased.
[2 marks]
As temperature increases, the resistance of the thermistor decreases.
The output pd will also decrease as pd is directly proportional to R and less pd will be supplied to the branch when resistance decreases.
Two acrobats of the same mass are suspended from ropes attached to opposite edges of a circular platform that is at the top of a vertical pole. A motor rotates the platform so that the acrobat move at constant speed in a horizontal circle on opposite sides of the pole. The centre of mass of each acrobat is 5m above the ground.
Discuss the consequences for the forces acting on the pole when one acrobat has a much greater mass than the other.
[3 marks]
Vertical compressive force on the pole increases.
If mass increases so does the weight and the tension as it counter acts weight.
Unbalanced horizontal forces on the pole which can cause it to sway to topple toward the most massive acrobat.
Centripetal force greater on more massive acrobat.
The force of gravity is considered negligible when discussing atomic interactions.
With reference to a property if subatomic particles explain why the gravitational force is negligible in the context of atomic interactions.
[3 marks]
Gravitational force is proportional to mass.
The mass of subatomic particles is extremely small, therefore, the gravitational force is negligible for subatomic masses.
Identify whether a bigger nucleus or smaller nucleus is more likely to be unstable and why.
[2 marks]
The bigger nucleus is more likely to be unstable, this is because unstable nuclei tend to have significant imbalance in the number of protons and neutrons.
Some subatomic particles are classified as hadrons. These are two classes of hadrons.
Discuss the nature of hadrons.
[6 marks]
Hadrons properties:
* Identifies hadrons as consisting of quarks
* May interact via the strong nuclear force
General structure:
* Two classes are mesons and baryons
* quark-antiquark: meson
* Quark, quark, quark: baryon
Stability of free hadron:
* Only stable free baryon is proton
* Example of decay of a free meson or baryon e.g. kaon decay into pions / states
neutron decays into a proton
For the conversion of a photon into an electron and positron, the photon must have an energy equal or greater than a certain amount energy.
[2 marks]
Energy of photon needs to provide at least the REST masses of the electron and positron.
A muon is an unstable particle.
State the names of the particles that are produced when a muon decays.
[1 mark]
electron+ electron antineutrino+ muon neutrino
In an experiment a speaker and receiver are two metres apart. A metal plate that reflects microwaves is parallel to the transmission and is moved further away from the speaker and the receiver.
Explains what happens to the signal detected by R as M is moved slowly towards X.
[4 marks]
Received signal goes through a series of maximal and minimal due to the reflected signals interfering with the direct ones.
Path length of the reflected waves increases as plate moves.
Phase difference between reflected and direct waves changes.
