As Exam Questions Flashcards
state and explain what feature of the graph shows that the car’s deceleration was uniform
the gradient respects the deceleration, the gradient is constant
state the difference between a scalar and vector quantity
vector quantise have direction and quality
two examples of vector quantity
displacement
velocity
state Hooke’s law
the amount of force is directly proportional to the extension up to the limit of proportional
explain what a stationary wave formed on the string
progressive waves travels from the centre to end
two progressive waves travel in opposite direction along the string
waves have same frequency (same amplitude)
explain why this light is totally internally reflected at the water surface
(critical angle)
angle of incidence exceeds critical angle
light passing through each slit spreads out. what is this effect?
diffraction
Explain the formation of the fringes seen on the screen
- inference
- where the light overlaps
- bright fringes are formed where the slits overlap
- dark fringes are formed when light cancel;s
- the light is coherent
- reinforcement occurs where light waves are in phase
- cancellation occurs when the waves are 180 out of phase
describe how the appearance of the fringes would differ if white light had been used instead of red light
-central fringe would be white
-side fringes of spetra
-dark fringes would be closer together
-bright fringe would be blue on the side nearest the centre
white fringes merge away from. the centre
-bright fringes wider
what is meant meant by an isotope
same number of proton but a different number of neutrons
explain what is meant by ground state of an atom and describe the process that is taking place in the atoms emitting photons.
Ground state is the lowest energy state. Photons are emitted when the atom is excited by gaining energy and when the atom dexcitates photons of different frequencies are emitted.
the electron moves down an energy level realising an proton
electron in atoms can only occupy certain energy levels
electrons collide with orbital electron
every particle will eventually decay to …
proton
state and explain the effect on the emitted electrons of increasing the frequency of the light
electron realised would have more kinetic energy and increasing the frequency of the protons increases
state and explain the effect on the emitted electrons of increasing the intensity of the light
more protons stake the metal surface so more electrons would be emitted
describe the procedure the student would follow in order to obtain an I-V curve for the semiconductor diode (6)
you would measure the current by using an ameter and the voltage through a voltmeter, you would plot the points on a graph with current on the x-axis and voltage on the y-axis. you would repeat the readings.
- make the circuit
- reverse the power supply to get negative readings
- vary the voltage
state and explain the effect on the oscilloscope trace if the time base is switched off
vertical line is formed
of length equal to twice peak voltage because the trace no longer moves horizontally
Write down one factor tyat could affect the drivers reaction time
Alchol
A fielder, as he catches the cricket ball he pulls his hand backwards
Explain why this action reduces the force on his hands
A cricketer lowers his hands while taking a catch to decrease the change of momentum, they increase the time by pulling in backwards
How does the resistance of a filament lamp change as the temperture of the filament change?
The resistance of the lamp increases as the temperature of filament increases so when the filament is hot then the resistance is high
Explain the difference between a transverse waves and longitudinal wave
Longtiudual waves
The vibrations are along the same direction as the direction of travel
Transverse waves
Osculate at right angel to the direction of movement
When the door is open, the person can hear the sound (from the TV) but cant see the television
Sound waves can diffract through the gap because the wavelength deceases
What happens during the process of nuclear fission
A nucleus hits the uranium nucleus which then splits realesing another neutron
Inside which part of the nuclear power station would molybdenum be produced
Nuclear reactor
What is meant by the term half-life
The amount of time needed for the number of nuclear atoms to half
Medical tracers are injected into the patients body. Explain the risk to the patient of using a radioactive substance as a medical tracer
The radioactive particles could ionise some cells in the body which could lead to cancer
What evidence is there that light is a wave
Light shows wave behaviour, it can be polarised, it diffracts and it can reflected and refracted
Does each meson consists of a quark and antiquark pair
True or false
True
Each baryon consist of three quarks.
True or false
True
The magnitude of the charge on every quark is 1/3
True or false
False
A particle consisting of a single quark has not been observed
True or false
True
Name the physical quantity that a particle must have to be acted on by an electromagnetic force
Must have a charge
Explain why mass isn’t necessarily conserved when particles interact and decay
Some of the mass is changed into energy
Name three other conservation laws that are obeyed in all nuclear interactions
Charge
Baryon number
Lepton number
State the type of interaction in which strangeness is conserved
Strong force
State the type of interaction in which strangeness is not conserved
Weak force
Under certain conditions a γ photon may be converted into an electron and a positron
Pair production
State the name of the antiparticle of a positron
Electron
State what would happen to the number of photoelectron ejected per second if the ultraviolet source were replaced by a source of red light of the same frequency but the less than the work function
No photoelectrons will be emitted
What would the wave theory of light predict about the effect of using the red light source instead of an ultraviolet source?
Photoelectron would be emitted because you would just use more than one which you cant do
Use the photon theory of light to explain the effect of using the red light source instead of an ultraviolet source
One photon of light can release one electron. A red light source doesn’t have enough energy to emit an electron, so nothing would happen when the photon hit the surface. The frequency is less than the work function
Give one example of each type of behaviour of electrons
Particle = photoelectric effect Wave = diffract
Explain how changes of electrons energies can produce a line emission spectrum
Dexcitation
Electrons must be excited to a higher energy state
Electron dexcitation producing an electron of specific wavelength
Must a specific colour
What is meant by ionisation
When an atom loses an electron
Name the constituent of an atom which has zero charge
Neutron
Name the constituent of an atom which has the largest specific charge
Electron
Name the constituent of an atom which has when remove leaves a different isotope of the element
Neutron
Explain why the photoelectric effect cannot be explained by the wave theory of light
Followed wave theory of light then the threshold frequency wouldn’t matter, the frequency wouldn’t effect if an electron could be emitted but it does
The teacher changes the metal to a sheet of glass. Then the reading on the sound meter when down. Why?
Some of the waves could go through the glass because it is less dense
Some of the microwaves transmitted by the speed gun are reflected form the moving ball towards the gun. Describe how the wavelength and frequency of the microwaves changes as they are reflected from the moving ball.
Wavelength decease
Frequency increase
What effect does the increases of ampltitude have on the loudness of the sound
Makes the sound louder
A fluorescent tube is filled with mercury vapour at low pressure. After mercury atoms have been excited they emit photons
Which part of the electromagnetic spectrum
UV
What is meant by an excited mercury atom?
An electron in atom is hit by another electron which gives the electron energy so it moves up a shell
How do the mercury atoms in the fluorescent tube become excited
Hits electrons in the atom
Transfer energy
Why do the excited mercury atoms emit photons of characteristic frequencies?
Fixed energy levels
specific amounts = specific frequencies
Explain how the coating on the inside of a fluorescent tube emits visible light
The uv light hits the coating which absorbs the photons and turns it into a lower frequency so it can be seen
Describe and explain one feature of the crane that prevents it from toppling over when it is lifting a container
The crane has a counterweight which creates an anticlockwise moment which contacts the clockwise moment if the container
Explain why the stopping distance is shorter than the value calculated
It would be should be slowed down by other resistive forces such as friction so the value would be less because energy is lost through heat
Which one of these are scalar A acceleration B force C momentum D energy
Energy (d)
Which of the following describe the properties of a vector
A vector has direction only
B vector has a value and direction
C vector has a value only
D vector is a quantity without units
B
Which one of the following is true about weight
A force measured in newtons
B measured in kilograms
C acts vertically upwards
D no forces that can balance the weight
A
Forces are in equilibrium when
A one force is bigger than a second force
B there are no force at all
C forces acting in random directions
D force all add up to zero
D
Which one of the following is not a force system is equilibrium
A a bridge carrying traffic across a river
B cricket ball being caught by a fielder
C aeroplane flying at a constant speed in level flight
D two tugs pulling a ship at a constant speed
B
State the principe of moments
The clockwise and anticlockwise moment equal each other provided its in equilibrium
Newtons first law states that
A every object continues in a state of test or uniform motion in a straight line unless acted on by an external force
B every object continues in a straight line regardless of what happens to it
C forces make object moves in circles
D no forces ever act on an object
A
A car reaches a maximum speed. The best explanation for this is that
A the engine has a limited speed it can run at
B the engine cannot exceed zero torque
C driving force from the engine is balanced by the weight of the car
D driving force from the engine is balance by drag and friction
D
Which one statement best describes newtons third law?
A forces act singly
B force act in pairs but only on a static body
C all forces have to add up to zero
D forces act in pairs, regardless of equilibrium or acceleration
D
What is meant by an ohmic conductir
Current is proportional to voltage
An experiment can be performed to determine whether a particular component is an ohmic conductor
- what measurements you would take
- how you would use your measurements
- how you would reach a conclusion
Vary the current ( variable resistance)
Regular intervals
Keep the temperature constant
You would measure both the ammeter and voltmeter. You would increase the voltage by 0.5v and measure the current. To find the resistance you would divid the voltage by the current. You would plot the voltage on the x-axis and current on the y-axis. The graph should be directly proportional I = V
What is meant by critical temperature
Temperature when the resistance is below zero
State the principal property of a superconductor
Zero resistance
State and explain what will happen to the reading on the voltmeter as the temperature of the thermistor increases
Increase
Temperature increase
Resistance decrease
State and explain what happens to the reading on the voltmeter if the intensity of the light incident on the LDR increase
The reading would increase because the resistance would decrease in the LDR so there would be more pd
Energy losses are estimated to reduce the output power for the turbine and generator to 60% of the value
State two reasons for this energy loss
Heat - electrical wires
Friction - turbine
The thrust on the car remains constant as the speed increases. Explain why the acceleration decreases and eventually reaches zero
The air resistance will keep increasing until they are equal, because it’s trying to overcome the force of the engine
Explain why air resistance is negligible in the vertical direction
The air resistance would mean that it wouldn’t go as far, air resistance in the vertical direction negligible because the air resistance blows horizontally not up and down
Explain how line spectra are produced
How the collisions of charged particles with gas atoms can cause the atoms to emit photons
How spectral lines are explained by the concept of discrete energy levels
Gas atoms can gain energy and excite
Causing it to move up an energy level
Electron in the outer shell will randomly dexcite
Energy emitted as a photon
The photons give off different energies
Discrete energy level means that they are specific amounts
State what happens to the momentum of the air as it passes through the engine
The velocity increasse
Explain using appropriate laws of motion, why the air exerts a force on the engine in the forward direction
Every action has an equal and opposite reaction
Firce acting on the air
Air exerts force on the engine of the same size
The speed of the air leaving b is the same as the speed of the deflected air. Explain why the momentum of the air changes
Momentum is a velocity
Change in air direction
Suggest why in practice the decelerating force provided by the deflector plates may not remain constant
The force might change because as you get lower there would be less wind so the amount would decrease.
Smaller rate of change of momentum
Explain why most microwave ovens contains a rotating turntable on which food is placed during cooking
Position of the antinode is constantly changing
What is meant by tensile stress
Amount of added force per area
What is meant by tensile strain
The amount if has stretched past its original length over the original
If the material is brittle then the line is …. Because there is no plastic deformation
Straight line
State and explain the effect on the current when the intensity of the electromagnetic radiation is increased
The current would increase because more photons would be released because there are more waves
The student increases the frequency of the electromagnetic radiation. Explain the effect this has on the stopping potential
The stopping potential would increase
Energy of the photons would be greater
Maximum kinetic energy of electrons
Explain why two photons are formed instead of a single photon when a helium nucleus annihilates with the anti-helium nucleus
Momentum must be conserved
So need two photons travelling in different directions
Explain why the ball wouldn’t travel this far before hitting the ground
Air resistance would slow the ball down so it wouldn’t reach so far
Define the moment of a force about a point
Force x distance between the line of action of the force to a point
explain
- in terms of photons why electrons are realised from the metals surface
- why the kinetic energy of the emitted varies up to a maximum value
if the photon has enough energy than it can realise a photoelectron from the surface of the metal. (This is called the photoelectric effect ). one photon can relate one electron. any excess energy is turned into kinetic energy. if where is less kinetic then photon lower in the metal wouldn’t be realised, so the work function is higher.
the exchange particle in this interaction was discovered by experiment with the rest mass that has been predicted. why is it important to test by experiment the prediction of a scientific theory?
if a reliable experiment does not support a hypothesis
the hypothesis must be changed
state what is meant by wave-particle duality of electrons
electrons can have wavelike properties and particle like properties
some materials exhibit the property of superconductivity under certain conditions
- state what is meant by superconductivity
- explain the required conditions for the material to become superconducting
- superconductivity means a material has zero resistivity/resistance
- resistivity decreases with temperature or idea of cooling
- becomes superconducting when you reach the critical/certain/transition temperature
state and explain what happens to the resistance of the cable when the embedded filament of wire are made superconducting
-the resistance decreases (to zero)
-copper still has resistance
-but this is in parallel with filaments (which have zero resistance)
-hence total resistance is zero!
current goes through filaments!
explain what is meant by the emf of the battery
work done (by the battery) per unit charge
explain what is meant by the internal resistance of the battery
the resistance of the materials within the battery
state and explain the effect of attempting to use a battery with a much higher internal resistance to start the car
car will probably not start
battery will not be able to provide enough current
state the class of particles to which w- belongs
exchange particle
name the only stable baryon
proton
explain in term of electron motion why the I-V characteristic for the filament lamp is a curve
the temperature increase so as more current goes through the lamp. the lattice ions vibrate more transferring energy making it more difficult for the electrons to pass.
explain how and why the maximum range of the wheelchair on level ground is affected by
- mass of the user
- speed at which the wheelchair travels
mass- more energy is needed to travel forwards so the range would decrease because the power is used for something else
speed- the wheelchair would reach terminal velocity. this means more energy is needed to overcome resistive forces so the range would decease
explain why the signal strength falls to a minimum between B and C and between C and D
path difference
creates a phase difference
destructive inference ( close to being 180 out of phase )
the intensity of the waves passing through each slit is the same
explain why the minimum intensity between C and D is not zero
the intensity of the diffracted waves decrease move over a further distance, so the wave from s1 would have a lower intensity between C and D as it has travelled further than the wave s2. so the waves would not be completely destructive
the vertical aerial is placed at position B and is rotated slowly through 90 (degrees) until it lies along the direction AE.
state and explain the effect on the signal strength as it is rotated
signal strength
light is polarised
signal is at a maximum at 0 then decreases and stops at 90
high winds produce large amplitudes of vibration of the aerial wire
explain why the wire may sag when the high wind stops
limit elasticity
wouldn’t reach to original shape
a) electrons are emitted in photoelectric effect experiments
b) electrons are released when atoms are ionised
c) electrons produce dark rings in diffraction experiments
d) electron transitions in atoms produce line spectra
c _ electrons produce sark rings in diffraction experiments
identify the state of an electron in the energy level labelled 0
ionisation
explain why the energy levels are negative
the amount of energy needed to release an electron
the student repeats her experiment using a wire of the same original length and metal but with a small diameter
discuss two way this change might affect the percentage uncertainty in the result for the young modulus
small diameter - might break - less readings- smaller range - larger uncertainties
stretched- bigger change in length- smaller percentage uncertainty
the scale on the meter has 50 divisions between zero and full-scale deflection
discuss why this meter is not suitable for carrying out the experiment
not a suitable scale because the maximum voltage measure would a tiny
before an earthquake occurs, the line being drawn on the graph paper is horizontal.
explain what happens to the line on the graph paper when an earthquake is detected and the frame of the seismometer accelerates rapidly downwards
pen would have up because pen accelerates less than the box
which one of following is not made of quarks a- kaon b-muon c-neuton c-pion
b
muon
in a diffraction-grating experiment the maxima are produced on a screen. what causes the separation of the maxima of the diffraction pattern to decrease ?
A using a light with a longer wavelength
B increasing the distance between the spacing and grating
C increasing the distance between the source and grating
D using a grating with a greater slit separation
D
white light passes through a single narrow slit and illuminates a screen. what is observed on the screen?
A-a set of equally spaced white fringes
B-a central maximum made up of a spectrum surrounded by white fringes
C-a white central maximum surrounded by coloured fringes
D-a single narrow white line
C
which of the following is correct when total internal reflection occurs?
A-the angle of incidence is less than the critical angle
B-the light meets an optically less dense medium
C-the light enters a medium with a higher refractive index
D- the angles that the incident and refracted rays make with the normal are the same
B
which is a scalar quantity? A-momentum B-weight C-power D-moment
Power (C)
can have a positive or a negative
a deep-space probe travelling forward at constant speed is briefly acted on by a force at right angles to its motion. what is the effect of this force on the forward speed and sideways speed of this probe?
A-forwards speed increases and sideways increase
B-forward speed decrease and sideways speed increase
C-forwards speed is unchanged and sideways speed increases
D-fowards speed decreases and sideways speed is unchanged
C
The mass of fuel in a racing car decrease during a race. As a result the lap time decrease. which of the following could explain this decrease?
A-there is less friction on the race track
B-maximum speed of the car has increased
C- maximum acceleration and deceleration are greater
D-engine is more efficient
C
What is represented by the area under a force-displacement graph? A-rate of change of kinetic energy B-change in momentrum C-work done D-acceleration
C
not momentum because force x displacement
a potential divider circuit consists of a battery connected across a thermistor and variable resistor in series. which of the following causes the potential difference (pd) across the thermistor to increase?
A-increasing the temperature of the thermistor
B-incraesing the resistance of the variable resistor
C-reducing the emf of the batter
D-adding a resistor across the variable resistor
D
