AQA GCSE Physics Revision

120 kJ in total: 95 kJ in the water's thermal store plus 25 kJ in the kettle/surroundings' thermal stores.

175 ÷ 500 = 0.35, so the efficiency is 35%.

Ek = ½mv² = ½ × 2.0 × 3.0² = 9.0 J.

P = E/t = 900/30 = 30 W.

Lubrication reduces friction, so less input energy is dissipated as thermal energy and a larger fraction remains for useful movement.

Wind reduces fuel combustion and operational carbon dioxide, but its variable output means the grid needs storage, transmission or other flexible generation to maintain supply.

Equal starting temperatures make the comparison fair so the difference in cooling is due to the insulation rather than initial conditions.

ΔE = mcΔθ = 0.50 × 4200 × 10 = 21,000 J.

It reduces friction, so less input energy is transferred to unwanted thermal stores and a larger fraction becomes useful output.

I = V/R = 6.0/3.0 = 2.0 A.

At the junction the branch currents add to the incoming current, so the other current is 2.0 − 0.7 = 1.3 A.

Q = It = 0.4 × 5 = 2 C.

It decreases: an NTC thermistor has a negative temperature coefficient.

50 Hz.

If it melts, it disconnects the live supply from the appliance. A fuse in only neutral could leave the appliance internally connected to live and dangerous.

2 minutes is 120 s; E = Pt = 60 × 120 = 7200 J.

Electrical energy is transferred to the element’s thermal store as moving electrons collide with the lattice ions.

A becomes negatively charged and B becomes positively charged.

From the positive plate towards the negative plate.

Keep the wire at constant temperature; measure potential difference across and current through it, then calculate R = V/I.

Increasing current heats its filament, increasing resistance, so current no longer rises proportionally with potential difference.

Put the ammeter in series with the resistor and the voltmeter in parallel across it.

For the same power, a higher potential difference requires a lower current; the cable-heating loss depends on current squared, so the loss is reduced.

Its volume is 47 − 35 = 12 cm³; density = 30/12 = 2.5 g/cm³.

ΔE = mcΔθ = 0.50 × 4200 × 4.0 = 8400 J.

No. Melting is a physical change and mass is conserved in the sealed system.

The particles’ arrangement and potential energy change; the supplied energy drives the state change rather than raising average kinetic energy.

E = mL = 0.20 × 80 000 = 16 000 J.

Pressure increases because the particles move faster and collide with the walls more frequently and forcefully.

The moving plunger does work on the gas, transferring energy to its internal energy and increasing its temperature.

Weigh the empty container, weigh it again with the liquid, and subtract the empty-container reading.

p₁V₁ = p₂V₂, so p₂ = (100 × 0.020)/0.010 = 200 kPa.

23 − 11 = 12 neutrons.

Gamma is the most penetrating of the three; thick lead or concrete reduces its intensity.

A long half-life means radioactive nuclei remain and decay over a long period, so the material can remain hazardous for longer; the actual risk also depends on activity and radiation type.

In its tiny central nucleus.

A 2+ ion has lost two electrons, so it has 12 − 2 = 10 electrons.

A small, dense, positively charged nucleus can strongly repel an alpha particle that passes close to it.

No. Individual decay is random, although a large sample has a predictable statistical pattern.

Mass number decreases by 4 and atomic number decreases by 2.

No. They were irradiated, but exposure to X-rays does not make their body contain radioactive material.

95 − 12 = 83 counts/min above background.

The benefit for exploring an organ or treating unwanted tissue, and the potential harm or risk to the patient, supported by the supplied data and consequences.

They absorb neutrons, controlling the rate of the chain reaction.

It joins light nuclei to make a heavier nucleus.

12 minutes, because the activity takes 12 minutes to halve.

The fraction remaining is 1/32, so the net decline is 1 − 1/32 = 31/32.

a = (10 − 4)/2 = 3 m/s².

F = ma = 4 × 1.5 = 6 N in the direction of its acceleration.

Initial momentum is 2×3 = 6 kg m/s. Total mass after is 3 kg, so v = 6/3 = 2 m/s in the original direction.

Displacement is a vector because it includes direction as well as a distance from the start point.

It is non-contact; the magnets exert forces without touching.

W = mg = 5 × 10 = 50 N.

25 − 17 = 8 N to the right.

W = Fs = 15 × 3 = 45 J.

k = F/x = 4/0.08 = 50 N/m.

M = 20 × 0.30 = 6.0 N m.

p = F/A = 100/0.5 = 200 Pa.

It doubles because Δp = ρgΔh and only Δh changes.

Zero, because the final position is the same as the starting position.

150 ÷ 3 = 50 km/h.

Its velocity includes the westward direction; its speed is only 12 m/s.

Gradient = 30/6 = 5 m/s.

18 + 24 = 42 m.

Tiredness can lengthen the driver’s reaction time, so the car travels farther before the brakes are applied.

Water reduces tyre-road grip, lowering the available braking force so more distance is needed to remove the vehicle’s kinetic energy.

It increases the time over which the passenger’s momentum changes, reducing the average force on the passenger.

p = mv = 3 × 4 = 12 kg m/s east.

F = Δp/Δt = 24/0.40 = 60 N.

Total initial momentum = 6 kg m/s east; combined mass = 3 kg, so shared velocity = 2 m/s east.

The difference is the extension; Hooke’s law relates applied force to extension, not to total spring length.

It halves, because a = F/m when resultant force stays fixed.

There is less air above the higher surface, so fewer air molecules collide with it and the air's weight per area is smaller.

Zero: the driving force balances the resistive forces, so its velocity does not change.

No. It is the object's tendency to maintain its motion; no resultant force is needed for constant velocity.

The book's downward contact force on the table; the two equal and opposite forces act on different objects.

Its velocity is constant and its acceleration is zero because the resultant force is zero.

The diagonal is 5 cm, which represents 10 N on the stated scale.

Towards the centre of the orbit, because the satellite's direction of motion is continually changing.

Gradient = 12/3 = 4 m/s.

The rectangular area is 6 × 5 = 30 m, so it travels 30 m.

m = F/a = 12/3 = 4 kg.

F = ma = 1200 × 5.0 = 6000 N, opposite the car's motion.

v = fλ = 25 × 0.80 = 20 m/s.

Ultraviolet has the shorter wavelength because its frequency is higher.

Longitudinal: air particles oscillate parallel to the direction the sound wave travels.

No. Sound needs a material medium whose particles can vibrate.

Seismic S-wave observations help reveal the structure and size of Earth's core, including evidence that part of it is liquid.

They are absorbed more by bone than by soft tissue, creating contrast at a detector.

Magnification = image height ÷ object height = 5.0/2.0 = 2.5, with no unit.

The filter transmits green wavelengths and absorbs much of the other visible light.

Matte black is the more effective emitter.

The intensity and wavelength distribution of its emission.

The absolute reading uncertainty is a smaller fraction of the longer total distance, so the calculated average wavelength is more reliable.

From the normal, the line perpendicular to the surface at the point of incidence.

Keep surface area and starting temperature the same; also maintain equal distance and measurement time.

Reflection, absorption and transmission.

From the normal, the line at 90° to the boundary.

250 mSv = 0.250 Sv, because 1000 mSv = 1 Sv.

Its speed changes in the new medium; the part of the wavefront that crosses first changes speed first, turning the front and the wave's direction.

An alternating current with the same frequency as the radio wave.

Their transmission through soft tissue differs from absorption by denser bone, creating contrast in the detected image.

They are equal; if absorption becomes faster than emission, the body's temperature rises.

Increase the current or add an iron core; winding the conductor into a solenoid also increases the magnetic effect compared with a straight wire.

A shift to a longer wavelength (toward the red end of the spectrum) indicates red-shift and recession.

The collapsing gas and dust causes fusion reactions to begin. In a stable star, expansion due to fusion energy balances gravitational collapse.

No. It becomes a red giant, sheds its outer layers and ends as a white dwarf.

Gravity provides the force that maintains its orbit around the planet or other central body.

It indicates the galaxy is receding faster, within the relationship described by the specification.

The radius must change; for a stable orbit, speed and radius cannot change independently.

They repel.

Where field lines are closest together, typically near the poles.

It becomes stronger.

The force direction reverses.

It keeps the torque acting in the same rotational direction so the motor continues to turn.

Alternating current reverses the motor-effect force on the coil, making it and the cone vibrate.

It falls to zero after any transient because the magnetic flux is no longer changing.

An alternator generates ac; a dynamo generates dc.

The sound-driven coil moves through a magnetic field, changing flux and inducing a potential difference.

Vs = 4 × 240 = 960 V. Input power equals output power, so Ip = 480/240 = 2.0 A.

Draw a tangent at that point and calculate its gradient, using displacement and time units.

They are precise because they cluster closely, but not accurate because they are not close to the true/reference value; a consistent offset suggests systematic error.

AT 8, observing waves in fluids and solids to identify suitable apparatus for studying interactions with matter, is Physics-only; AT 6 concerns electrical measurements and component characteristics.

c = E/(mΔθ) = 6000/(0.40 × 15) = 1000 J/(kg °C).

Cause and effect: an unbalanced resultant force causes acceleration, changing the object's velocity.

E = Pt; energy is in joules, power in watts and time in seconds.

Is = VpIp/Vs = (12 × 0.50)/24 = 0.25 A.