GCSE physics - 6 markers

⚙️ Section 1 – Motion, Forces, and Conservation of Energy

Explain how Newton's three laws of motion apply to a rocket taking off from Earth.

Newton’s First Law (Inertia):

A stationary rocket remains at rest unless acted on by a resultant force.

Once engines fire and thrust > weight, the unbalanced force causes the rocket to accelerate upwards.

Newton’s Second Law (Force = Mass × Acceleration):

The acceleration of the rocket depends on its mass and the resultant force: F=maF = maF=ma.

As fuel is used, the rocket's mass decreases → acceleration increases if force remains the same.

Newton’s Third Law (Action-Reaction):

Rocket engines push exhaust gases downwards.

Gases exert an equal and opposite force upwards on the rocket → lift-off occurs due to this reaction force.

Describe how energy is transferred and conserved when a ball is thrown vertically upwards and falls back down.

Initial energy transfer:

Chemical energy (from muscles) is transferred to the ball as kinetic energy when it is thrown.

During upward motion:

As the ball rises, kinetic energy decreases.

Energy is converted into gravitational potential energy (GPE) as the ball gains height.

At the highest point:

Ball’s GPE is at its maximum.

Kinetic energy is zero (momentarily stationary).

During downward motion:

GPE converts back to kinetic energy as the ball accelerates downward.

Ball gains speed as it falls due to gravity.

Energy conservation:

Total energy is conserved throughout (no energy is lost).

Some energy is transferred to thermal energy due to air resistance, but this is still part of the energy system.

Explain how stopping distance is affected by speed, road conditions, and the reaction time of a driver.

Stopping distance = Thinking distance + Braking distance

Thinking distance:

Depends on reaction time of the driver.

Longer reaction time = longer thinking distance.

Influenced by:

Alcohol, drugs, tiredness, distractions (e.g. phone use).

Speed – higher speed = further distance travelled during reaction time.

Braking distance:

Depends on:

Speed (more kinetic energy to remove).

Road surface (wet, icy, or uneven increases distance).

Tyre and brake conditions (worn tyres or brakes reduce grip).

As speed increases, braking distance increases more than proportionally due to KE=12mv2KE = \frac{1}{2}mv^2KE=21​mv2.

Conclusion:

Stopping distance increases significantly with speed and worsens with poor road conditions or driver alertness.

Understanding this helps reduce risk of accidents.

Discuss how friction and air resistance influence the motion of a vehicle and how energy is dissipated.

Friction:

Acts between tyres and road and within mechanical parts of the car (e.g. engine, gearbox).

Opposes motion, converting kinetic energy to thermal energy.

Air resistance (drag):

Increases with the speed of the vehicle.

Opposes the forward motion by pushing back against the car.

Effect on motion:

Both forces resist the vehicle’s movement → require the engine to do work to overcome them.

Without enough force from the engine, the vehicle will decelerate.

Energy dissipation:

Energy from fuel is transferred into kinetic energy to keep the car moving.

Some energy is unintentionally transferred to surroundings as heat and sound due to friction and air resistance.

These are considered wasted or dissipated energy → reduce efficiency of the vehicle.

Efficiency link:

The more friction/air resistance, the more energy is needed → reduces fuel efficiency.

Section 2 – Waves and the Electromagnetic Spectrum

Compare how transverse and longitudinal waves transfer energy and give examples of each.

Wave types:

Transverse waves: Oscillations are perpendicular to the direction of energy transfer.

Longitudinal waves: Oscillations are parallel to the direction of energy transfer.

Examples:

Transverse: All electromagnetic (EM) waves (e.g. light, radio waves), water waves.

Longitudinal: Sound waves, seismic P-waves.

How energy is transferred:

Both types of waves transfer energy without transferring matter.

In transverse waves, energy moves as peaks and troughs (e.g. ripples on water).

In longitudinal waves, energy moves through compressions and rarefactions in the medium.

Medium requirement:

Longitudinal waves like sound require a medium (solid, liquid, gas).

EM waves (transverse) can travel through a vacuum (no medium needed).

Key difference:

Direction of oscillation relative to direction of wave travel.

Explain how the wave equation v = fλ applies to sound waves travelling through different materials.

Wave equation:

v=fλv = f \lambdav=fλ: wave speed = frequency × wavelength.

Sound wave behaviour:

Sound is a longitudinal wave that travels by particle vibration.

The speed of sound depends on the medium:

Fastest in solids, slower in liquids, slowest in gases.

This is because particles are more tightly packed in solids → vibrations transfer faster.

When changing medium:

Frequency stays the same (determined by source).

Wavelength changes depending on the speed of the wave in the new material.

So, if sound travels faster in a solid than in air, the wavelength increases.

Example:

If a sound wave enters water from air, speed increases → longer wavelength, same frequency.

Key understanding:

Wave speed changes with medium → affects wavelength, not frequency.

Describe how total internal reflection occurs and how this principle is used in optical fibres.

Total internal reflection (TIR):

Occurs when light travels from a more dense to a less dense material (e.g. glass → air).

If the angle of incidence is greater than the critical angle, the light is reflected entirely inside the material.

No refraction occurs → 100% reflection within the material.

Conditions for TIR:

Light must be in more optically dense medium.

Angle of incidence > critical angle for that material.

Use in optical fibres:

Light signals are sent down the fibre and bounce internally by total internal reflection.

Allows the signal to travel long distances with minimal energy loss.

Common in telecommunications and medical instruments (endoscopes).

Why TIR is useful:

Ensures clear, reliable transmission of data without scattering or loss.

Maintains signal strength and direction over long distances.

Compare visible light, ultraviolet, and X-rays in terms of wavelength, frequency, and their uses and dangers.

Wavelength & frequency (part of EM spectrum):

All three are electromagnetic waves.

X-rays: Shortest wavelength, highest frequency.

Ultraviolet (UV): Shorter wavelength than visible, but longer than X-rays.

Visible light: Longer wavelength, lower frequency than UV and X-rays.

Penetration ability:

X-rays: Very penetrating, pass through soft tissue but absorbed by bone → used in imaging.

UV: Less penetrating, can cause damage to skin cells (sunburn, cancer risk).

Visible light: Safe to human tissue, used for vision and illumination.

Uses:

X-rays: Medical imaging, security scanning.

UV: Sterilising equipment, detecting security markings, tanning beds.

Visible light: Photography, lighting, fibre optics.

Dangers:

X-rays and UV are ionising radiation → can damage DNA → lead to cancer or mutations.

Protection is needed (lead aprons for X-rays, sunscreen for UV).

Summary:

As frequency increases, so does energy and risk of ionisation.

Higher energy waves (UV, X-rays) have greater medical uses, but also greater hazards.

Section 3 – Radioactivity and Astronomy

Describe how the use of radioactive isotopes in medicine takes advantage of their properties.

Radioactive isotopes (tracers or treatment):

Used in diagnosis (tracers) and treatment (e.g. cancer therapy).

Medical tracers:

Radioisotope is injected or swallowed and travels through the body.

Emits gamma radiation, which is detected outside the body using a gamma camera.

Gamma rays are ideal as they penetrate tissue but are weakly ionising.

Isotopes used have short half-lives → reduce radiation dose to patient.

Cancer treatment (radiotherapy):

High-energy gamma or beta radiation is focused on tumour to kill cancer cells.

Careful planning limits damage to surrounding healthy tissue.

Sometimes radioactive implants (e.g. beta emitters) are placed inside the body.

Key properties used:

Type of radiation (gamma for detection, beta/gamma for treatment).

Explain what half-life means and how it can be used to determine the age of ancient objects.

Definition of half-life:

The time taken for half the radioactive nuclei in a sample to decay.

Alternatively, the time taken for the activity (count rate) to fall to half its original value.

Decay is random:

Individual decays cannot be predicted, but large numbers follow predictable half-life behaviour.

Carbon dating:

Living things take in carbon-14 while alive.

After death, carbon-14 decays and is not replaced.

Scientists measure the amount of carbon-14 remaining in a sample.

Comparing this to the original level gives an estimate of age, using the known half-life (~5730 years).

Why it's useful:

Used to date organic materials like wood, bone, or cloth.

Other isotopes (e.g. uranium) used for dating rocks and fossils with longer timescales.

Compare the processes occurring in stars of different sizes after they run out of hydrogen fuel.

All stars begin with hydrogen fusion in the core (main sequence stage).

Low-mass stars (like the Sun):

Hydrogen runs out → star expands into a red giant.

Helium and other elements fuse in the core.

Outer layers are ejected → form planetary nebula.

Core remains as a white dwarf → eventually cools to become a black dwarf.

High-mass stars:

Hydrogen runs out → expand into red supergiant.

Heavier elements fuse up to iron.

Core collapses → supernova explosion.

Core remnants form either a neutron star or a black hole (if very massive).

Key differences:

High-mass stars end in violent explosions (supernova), low-mass stars do not.

End products differ: white dwarf vs. neutron star or black hole.

Both pathways enrich the universe:

Supernovae spread heavier elements into space → essential for forming new stars and planets.

Explain how observations of redshift and cosmic microwave background radiation provide evidence for the Big Bang.

Redshift:

Light from distant galaxies is redshifted — wavelengths are stretched.

Shows galaxies are moving away from us → Universe is expanding.

Greater redshift = greater distance = faster movement → suggests space itself is stretching.

Hubble's Law:

Direct relationship between a galaxy’s distance and its speed → supports expansion theory.

Cosmic Microwave Background Radiation (CMBR):

Uniform radiation detected from all directions in space.

Remains of the heat from the Big Bang, now cooled to ~2.7K.

CMBR is only explained by a hot, dense early Universe — strong evidence for Big Bang theory.

Combined evidence:

Redshift shows current expansion.

CMBR shows past state of hot, dense matter.

Both support the Big Bang theory as the best model for the origin of the Universe.

Section 4 – Forces and Energy (Doing Work & Effects)

Describe an experiment to investigate how the extension of a spring depends on the force applied.

Apparatus:

Clamp stand, spring, metre ruler, weights, pointer or marker, mass hanger.

Method:

Measure the original length of the spring without any load.

Add weights one at a time (e.g. 1 N increments).

After each weight, measure the new length of the spring.

Calculate extension = new length – original length.

Repeat and record for each load.

Variables:

Independent variable: force (weight added).

Dependent variable: extension.

Control variables: type of spring, increments of weight, same measurement setup.

Analysis:

Plot a graph of extension vs. force.

Should get a straight line if within elastic limit (Hooke’s Law: F=kxF = kxF=kx).

Conclusion:

Extension is directly proportional to force until the limit of proportionality is exceeded.

Explain the difference between scalar and vector quantities and give examples of each.

Scalars:

Quantities that have magnitude only, no direction.

Examples: Speed, distance, mass, temperature, energy.

Vectors:

Quantities that have both magnitude and direction.

Examples: Velocity, displacement, acceleration, force, momentum.

Key difference:

Vectors need a direction to be fully described, while scalars don’t.

Illustration with motion:

A car travelling at 30 m/s (scalar) has speed.

A car travelling at 30 m/s north (vector) has velocity.

Two objects could have the same speed but different velocities if they’re moving in different directions.

Displacement vs. Distance:

Distance is the total path length (scalar).

Displacement is the straight line change in position (vector).

Describe how work is done when a person climbs stairs and how this relates to gravitational potential energy.

Work done definition:

Work is done when a force moves an object over a distance: W=F×dW = F \times dW=F×d.

Climbing stairs:

Person applies a force upwards equal to their weight (mass × gravity).

Moves a vertical distance (height) → work is done against gravity.

Energy transfer:

Chemical energy (from muscles) → kinetic energy (while climbing) → gravitational potential energy (GPE).

GPE gained:

GPE=mgh\text{GPE} = mghGPE=mgh, where:

mmm = mass,

ggg = gravitational field strength (9.8 N/kg),

hhh = vertical height climbed.

Conservation of energy:

The energy used to do work becomes stored GPE.

Some energy is also transferred to thermal energy due to inefficiencies (e.g. friction in joints, heat in muscles).

Explain how pressure in a liquid changes with depth and how this principle applies to submarines.

Liquid pressure:

Increases with depth due to the weight of water above.

Formula: P=hρgP = h \rho gP=hρg

hhh: depth,

ρ\rhoρ: density of the liquid,

ggg: gravitational field strength.

Why it increases:

More water above = greater weight pressing down.

So, deeper = more pressure.

Application to submarines:

Submarines experience higher pressure as they go deeper underwater.

Must be specially designed to resist large pressure differences.

If pressure inside isn’t balanced, structure could collapse (implosion).

Other uses of liquid pressure:

Dams are thicker at the base to withstand higher pressure at greater depths.

Hydraulic systems use liquid pressure to multiply force.

Section 5 – Electricity and Circuits

Explain how the resistance of a wire depends on its length, thickness, and the material it's made from.

Resistance Formula:

The resistance of a wire is given by the formula R=ρLAR = \rho \frac{L}{A}R=ρAL​, where:

RRR = resistance,

ρ\rhoρ = resistivity of the material,

LLL = length of the wire,

AAA = cross-sectional area (related to thickness).

Length of wire:

As the length increases, the resistance increases.

Longer wires have more atoms for electrons to collide with, increasing energy loss in the form of heat.

Thickness of wire:

As the thickness increases, the resistance decreases.

A wider wire allows more space for electrons to flow, reducing the chance of collisions and lowering resistance.

Material of wire:

Different materials have different resistivity (a property that indicates how much the material resists the flow of electrons).

Metals like copper have low resistivity → low resistance.

Materials like rubber have high resistivity → high resistance.

Conclusion:

Resistance is directly proportional to the length of the wire, inversely proportional to the thickness, and depends on the resistivity of the material.

Compare current and potential difference in series and parallel circuits and explain how they affect component performance.

Series Circuits:

Current: The same current flows through all components in a series circuit.

If one component breaks, the entire circuit is broken and no current flows.

Potential Difference (Voltage): The total voltage is shared between the components.

Vtotal=V1+V2+⋯+VnV_{\text{total}} = V_1 + V_2 + \dots + V_nVtotal​=V1​+V2​+⋯+Vn​.

Higher resistance components take a larger share of the voltage.

Effect on components:

Resistors in series: Each resistor gets a portion of the voltage, meaning the current stays the same but is divided based on resistance.

Parallel Circuits:

Current: The total current splits between the branches according to the resistance in each branch.

The branch with the lowest resistance gets the most current.

Potential Difference (Voltage): The same voltage is applied across each branch.

Vbranch=VtotalV_{\text{branch}} = V_{\text{total}}Vbranch​=Vtotal​.

Effect on components:

Each branch can have a different current depending on the resistance of that branch.

Adding more branches decreases the overall resistance of the circuit.

Summary:

In a series circuit, current is the same but voltage is shared; in a parallel circuit, voltage is the same but current is divided.

Series circuits are useful when you want all components to be powered equally (e.g., in Christmas lights).

Parallel circuits are preferred for electrical wiring in homes because if one component fails, others still work.

Describe how to investigate the relationship between current and voltage for a resistor and a filament lamp.

Apparatus:

Power supply, ammeter, voltmeter, resistor, filament lamp, variable resistor.

Method (for resistor):

Set up the circuit with the resistor, ammeter, and voltmeter in a series configuration.

Vary the voltage by adjusting the power supply or using a variable resistor.

Record the current and voltage for each setting.

Plot a current vs. voltage graph.

Expected result:

For a resistor, the graph will show a linear relationship, meaning Ohm's Law applies: V=IRV = IRV=IR, where the resistance remains constant.

Method (for filament lamp):

Set up the same circuit but replace the resistor with the filament lamp.

Repeat the process of varying voltage and measuring current.

Plot the graph of current vs. voltage.

Expected result:

For a filament lamp, the graph will show a non-linear relationship.

Initially, the current increases as voltage increases, but as the filament heats up, the resistance of the lamp increases, causing the current to rise at a slower rate.

The graph will curve and show that the resistance is not constant as with the resistor.

Conclusion:

For a resistor, resistance is constant (linear graph, Ohm's law).

For a filament lamp, resistance changes as the temperature of the filament increases (non-linear graph).

Explain how fuses and circuit breakers work to protect electrical appliances and users.

Fuses:

A fuse is a safety device made of a thin wire that melts when the current exceeds a certain level.

How it works:

If the current is too high (due to a fault or overload), the fuse wire melts, breaking the circuit and stopping the flow of electricity.

This protects appliances from damage caused by excess current (e.g., overheating).

Types of fuses:

Fuses come in different ratings (e.g., 3A, 5A, 13A) to protect different devices.

Circuit Breakers:

A circuit breaker is an electronic device that automatically switches off the circuit when an overload or short circuit occurs.

How it works:

Circuit breakers have a mechanical switch that is triggered by a magnetic or thermal mechanism when the current is too high.

When the switch is triggered, the breaker disconnects the circuit.

Advantages of circuit breakers:

Can be easily reset after being tripped (unlike fuses, which need to be replaced).

Faster response to electrical faults compared to fuses.

Key difference:

Fuses need to be replaced after use, whereas circuit breakers can be reset.

Summary:

Both fuses and circuit breakers are important safety devices that protect users and appliances from electrical damage caused by overcurrent. They work by breaking the circuit when the current exceeds a safe level.

Section 6 – Electric and Magnetic Fields

Explain how the motor effect is used to make an electric motor turn.

Motor Effect:

The motor effect occurs when a current-carrying wire is placed in a magnetic field and experiences a force.

This force is caused by the interaction between the magnetic field and the electric current (moving charges) in the wire.

How an Electric Motor Works:

An electric motor contains a coil of wire (armature) placed within a magnetic field.

When current passes through the coil, the motor effect causes the coil to experience a force, which makes it rotate.

The direction of rotation is given by the Fleming's left-hand rule:

Thumb: Direction of force (motion).

First finger: Direction of magnetic field (from north to south).

Second finger: Direction of current (conventional flow).

To keep the coil rotating continuously, a commutator is used to reverse the direction of current in the coil at the right moments, ensuring continuous rotation.

Key Features of the Motor:

The strength of the force depends on the current, magnetic field strength, and length of the wire in the magnetic field.

By increasing the current or using stronger magnets, the motor can turn faster or with more torque.

Conclusion:

The motor effect is the basis of electric motors, where a current-carrying wire experiences a force in a magnetic field, causing it to rotate.

Describe how electromagnetic induction is used in transformers and why they are important in the National Grid.

Electromagnetic Induction:

Electromagnetic induction occurs when a changing magnetic field induces an electric current in a conductor.

In a transformer, alternating current (AC) in the primary coil generates a changing magnetic field, which induces a current in the secondary coil through the process of electromagnetic induction.

How Transformers Work:

Primary coil: AC current flows through the primary coil, creating a changing magnetic field in the iron core.

Iron core: The magnetic field is concentrated and passed through the iron core, increasing the efficiency of the transformation.

Secondary coil: The changing magnetic field induces an alternating current in the secondary coil, which can be stepped up or stepped down depending on the number of turns in the primary and secondary coils.

Transformers and the National Grid:

Step-up transformers increase the voltage for efficient transmission over long distances.

High voltage reduces energy loss due to resistance in the wires (since P=I2RP = I^2RP=I2R, higher current results in more heat loss).

Step-down transformers decrease the voltage at the point of use, making it safe for consumers.

Transformers are essential in the National Grid to allow electricity to be transmitted over long distances at high voltages and then reduced to a safer level for domestic use.

Conclusion:

Transformers use electromagnetic induction to transfer electrical energy between two coils, stepping up or stepping down the voltage, and are crucial for efficient power distribution in the National Grid.

Explain how a charged object can attract neutral objects using electric fields.

Electric Fields and Charging:

A charged object creates an electric field around it. The direction and strength of this field depend on the type of charge (positive or negative).

Attraction of Neutral Objects:

A neutral object has equal numbers of positive and negative charges.

When a charged object is brought near a neutral object, the electric field of the charged object causes the electrons (negatively charged particles) in the neutral object to move.

If the charged object is positive, the electrons in the neutral object are attracted towards the positive charge, creating a region of negative charge near the charged object.

If the charged object is negative, the electrons are repelled, leaving a region of positive charge near the object.

This separation of charges creates an attractive force between the charged object and the neutral object, causing the neutral object to be attracted to the charged object.

Example:

A charged balloon can attract small pieces of paper, even though the paper is neutral, because the balloon’s electric field causes the paper's electrons to move and become temporarily polarized.

Conclusion:

A charged object can attract a neutral object by inducing a separation of charges within the neutral object, resulting in an attractive force due to the electric field.

Describe how the direction and strength of a magnetic field can be investigated using a compass and iron filings.

Using a Compass to Investigate Magnetic Fields:

A compass can be used to detect the direction of a magnetic field.

The needle of the compass is a small magnet and it aligns itself with the magnetic field lines.

By placing the compass at various points around a magnet, the direction of the magnetic field can be mapped out by observing the direction the needle points.

The field lines will point away from the north pole of a magnet and towards the south pole.

Using Iron Filings to Investigate Magnetic Fields:

Iron filings can be sprinkled around a magnet to visually represent the magnetic field lines.

When sprinkled over a sheet of paper with a magnet underneath, the iron filings align along the magnetic field lines, showing the shape and pattern of the magnetic field.

Strong magnetic fields are represented by densely packed lines, indicating stronger magnetic forces, while weaker fields are shown with more spread-out lines.

Investigating the Strength of the Field:

The strength of the magnetic field can be measured by the spacing of the lines: the closer the lines, the stronger the field.

The field strength is strongest at the poles of the magnet and weakest at the equator.

Conclusion:

The direction and strength of a magnetic field can be studied by using a compass to show direction and iron filings to reveal the pattern and strength of the field.