Original open focus revision; complete specification coverage remains unfinished.
1 · Motion graphs and acceleration
velocity · acceleration
edexcel_ial_physics:motion:open:1 · 2 баллов
What does area under a velocity-time graph represent?
- Вытеснение
- Ускорение
- Масса
Ответ и обоснование
Вытеснение
- The gradient of a displacement-time graph is velocity. The area under a velocity-time graph gives displacement. A constant-acceleration formula is valid only when its assumption is justified.
edexcel_ial_physics:motion:open:2 · 4 баллов
Velocity changes from 3 to 15 metres per second in 6 s. Find acceleration.
Ответ и обоснование
2 m/s²
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
Negative velocity indicates direction under the chosen sign convention; it does not necessarily mean slowing down.
2 · Forces, momentum and safe stopping
momentum · resultant force
edexcel_ial_physics:forces:open:1 · 2 баллов
For fixed momentum change, which reduces average stopping force?
- Longer stopping time
- Shorter stopping time
- Ignoring external force
Ответ и обоснование
Longer stopping time
- Impulse equals momentum change. Increasing stopping time for the same momentum change reduces average force. Identify external forces before applying momentum conservation.
edexcel_ial_physics:forces:open:2 · 4 баллов
A 2 kg trolley travels at 3 metres per second. Find its momentum.
Ответ и обоснование
6 kg·m/s
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
Balanced forces do not require the object to be at rest. Mass and weight have different units and meanings.
3 · Energy stores, work and efficiency
power · efficiency
edexcel_ial_physics:mechanical_energy:open:1 · 2 баллов
What happens to kinetic energy when speed doubles at fixed mass?
- It doubles
- It quadruples
- It stays constant
Ответ и обоснование
It quadruples
- Define the system and useful output before calculating efficiency. Doubling speed quadruples kinetic energy at constant mass. Power describes transfer per time, not total energy.
edexcel_ial_physics:mechanical_energy:open:2 · 4 баллов
A device receives 250 J and gives 150 J useful output. Find efficiency as a percentage.
Ответ и обоснование
60 %
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
Efficiency cannot exceed 100% for a properly defined energy balance. Energy dissipated by heating is still conserved.
4 · Waves, measurement and refraction
wavelength · frequency
edexcel_ial_physics:waves:open:1 · 2 баллов
When a wave enters a slower medium, what stays constant?
- Частота
- Длина волны
- Скорость
Ответ и обоснование
Частота
- At a boundary, frequency stays fixed by the source. A change of speed changes wavelength. Refraction follows from speed differences; angles are measured from the normal.
edexcel_ial_physics:waves:open:2 · 4 баллов
Frequency is 8 Hz and wavelength is 0.25 m. Find wave speed.
Ответ и обоснование
2 m/s
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
The wave frequency does not change simply because the medium changes. A longitudinal wave has oscillations parallel to propagation.
5 · Current, potential difference and resistance
current · potential difference
edexcel_ial_physics:circuits:open:1 · 2 баллов
How is a voltmeter connected to measure voltage across a resistor?
- In parallel with the resistor
- In series only
- Across the ammeter only
Ответ и обоснование
In parallel with the resistor
- Current is the same through components in series. Potential differences add around the series path. In parallel, branches share the same potential difference, while branch currents sum at a junction.
edexcel_ial_physics:circuits:open:2 · 4 баллов
A component has 12 V across it and carries 0.40 A. Find resistance.
Ответ и обоснование
30 Ω
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
Current is not used up by a lamp. A filament heats up, so its resistance need not remain constant as voltage changes.
6 · Photons and the photoelectric effect
photon · work function
edexcel_ial_physics:quantum:open:1 · 2 баллов
At fixed above-threshold frequency, increasing intensity mainly increases what?
- Энергия фотона
- The number of emitted electrons per time
- Work function
Ответ и обоснование
The number of emitted electrons per time
- Use photon energy = Planck constant × frequency. Maximum kinetic energy = photon energy - work function. Increasing intensity at fixed frequency increases photon arrival rate, not individual photon energy.
edexcel_ial_physics:quantum:open:2 · 4 баллов
Photon energy is 4.8 eV and work function 2.1 eV. Find maximum kinetic energy.
Ответ и обоснование
2.7 eV
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
Electrons do not accumulate many sub-threshold photons in the elementary single-photon model. Do not confuse photon number with photon energy.
7 · Uncertainty, gradients and model testing
uncertainty · systematic error
edexcel_ial_physics:uncertainty:open:1 · 2 баллов
Which is most likely a systematic error?
- A balance reads 0.20 g when empty
- Repeated values fluctuate either side of the mean
- Random differences in reaction time
Ответ и обоснование
A balance reads 0.20 g when empty
- For a product or quotient, adding fractional uncertainties is a common maximum-uncertainty approximation. For a difference, add absolute uncertainties. A nonzero intercept can reveal an offset or an incomplete model.
edexcel_ial_physics:uncertainty:open:2 · 4 баллов
A 40 cm reading has an absolute uncertainty of 1 cm. Find percentage uncertainty.
Ответ и обоснование
2.5 %
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
Repeating readings reduces random uncertainty in a mean but does not automatically remove a zero error. Do not quote more decimal places than your measurement can support.
8 · Fields, motors and induction
induction · transformer
edexcel_ial_physics:fields:open:1 · 2 баллов
Which gives a continuing emf in a coil?
- A constant unchanging flux
- A changing flux linkage
- A nearby stationary magnet in every situation
Ответ и обоснование
A changing flux linkage
- Changing field strength, coil area, orientation or relative motion can change flux linkage. Lenz law describes an induced effect opposing the change producing it, consistent with energy conservation.
edexcel_ial_physics:fields:open:2 · 4 баллов
An ideal transformer has Np=400, Ns=100 and Vp=20 V. Find Vs.
Ответ и обоснование
5 V
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
A transformer needs changing magnetic flux; a steady DC input does not provide continuous transformer action. Magnetic field direction is not automatically the direction of force.
9 · Gravitational fields and orbital motion
gravitational field · centripetal force
edexcel_ial_physics:gravitation:open:1 · 2 баллов
What direction is the net force in uniform circular motion?
- Toward the centre
- Along the velocity
- Always outward
Ответ и обоснование
Toward the centre
- For a point mass or outside a spherical mass, field strength follows an inverse-square distance dependence. Use distance from the centre, not height above the surface alone.
edexcel_ial_physics:gravitation:open:2 · 4 баллов
Field strength is 18 units at r. Find it at 3r for an inverse-square field.
Ответ и обоснование
2
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
Weightlessness in an orbiting spacecraft means apparent weight is small in free fall, not that there is no gravitational field.
10 · Thermal measurements and particle models
specific heat capacity · latent heat
edexcel_ial_physics:thermal:open:1 · 2 баллов
Why can temperature stay constant while a pure substance melts?
- No energy enters
- Energy changes particle arrangement
- The thermometer must be broken
Ответ и обоснование
Energy changes particle arrangement
- Temperature relates to particle motion in a model; internal energy includes kinetic and potential contributions. During a change of state, energy can change particle arrangements rather than temperature.
edexcel_ial_physics:thermal:open:2 · 4 баллов
A 2 kg sample with c=500 J per kilogram per degree warms by 3 °C. Find energy gain.
Ответ и обоснование
3000 J
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
A flat section of a heating curve can show a phase change, not absence of energy transfer. Do not substitute temperature for a temperature difference in E = mcΔT.
11 · Gas models and absolute temperature
absolute temperature · ideal gas
edexcel_ial_physics:gases:open:1 · 2 баллов
Which scale belongs in a gas-law temperature ratio?
- Celsius
- Kelvin
- Either scale without conversion
Ответ и обоснование
Kelvin
- At fixed amount and volume, pressure is proportional to kelvin temperature. At fixed temperature and amount, pressure is inversely proportional to volume. State which quantities are fixed before choosing a relationship.
edexcel_ial_physics:gases:open:2 · 4 баллов
At fixed volume, pressure is 120 kPa at 300 K. Find pressure at 350 K.
Ответ и обоснование
140 kPa
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
An ideal gas is a model with conditions of validity. Celsius zero is not zero molecular motion, and internal energy is not determined by pressure alone.
12 · Nuclear changes and radiation evidence
half-life · background radiation
edexcel_ial_physics:nuclear:open:1 · 2 баллов
Which count should be used for source activity?
- Raw source-plus-background only
- Measured count minus background over equal times
- The largest repeated count only
Ответ и обоснование
Measured count minus background over equal times
- Subtract background counts measured over the same time interval. Distinguish irradiation from contamination. Shielding, distance and reduced exposure time can reduce risk under a school-controlled procedure.
edexcel_ial_physics:nuclear:open:2 · 4 баллов
An initial source count is 160 per minute. Find it after three half-lives.
Ответ и обоснование
20 counts/min
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
An irradiated object is not automatically radioactive. A half-life does not predict the exact decay time of one nucleus.
13 · Oscillation, resonance and phase
resonance · damping
edexcel_ial_physics:oscillations:open:1 · 2 баллов
For ideal SHM, where is speed greatest?
- At equilibrium
- At maximum displacement
- At every point equally
Ответ и обоснование
At equilibrium
- Velocity is greatest near equilibrium for ideal SHM, while acceleration magnitude is greatest at extreme displacement. Resonance can occur near the natural frequency under periodic driving, with amplitude limited by damping.
edexcel_ial_physics:oscillations:open:2 · 4 баллов
30 cycles take 45 s. Find period.
Ответ и обоснование
1.5 s
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
Not every repeated motion is SHM. A force proportional to displacement but directed away from equilibrium does not produce SHM.
14 · Stars, radiation and scale
luminosity · flux
edexcel_ial_physics:space:open:1 · 2 баллов
At fixed luminosity, what happens to flux when distance doubles?
- It halves
- It becomes one quarter
- It doubles
Ответ и обоснование
It becomes one quarter
- For isotropic emission without absorption, flux follows an inverse-square relationship with distance. Observed brightness alone therefore cannot establish luminosity.
edexcel_ial_physics:space:open:2 · 4 баллов
A source gives flux 18 units. Find flux at three times the distance.
Ответ и обоснование
2
- Appropriate relation; consistent substitution; correct result; meaningful unit and interpretation.
The Sun is not expected to become a supernova. Redshift can support cosmological expansion; it does not mean every nearby object must move away from every observer.