paper 2 !!!!! xxxxxx

what r vector quantities and how represented and example

Vector quantities have magnitude and an associated direction.

A vector quantity may be represented by an arrow. The length of the arrow represents the magnitude, and the direction of the arrow the direction of the vector quantity.

Force is a vector quantity.

what r scalar quantities

Scalar quantities have magnitude only.

what is weight and what dependent on

Weight is the force acting on an object due to gravity. The force of gravity close to the Earth is due to the gravitational field around the Earth.

The weight of an object depends on the gravitational field strength at the point where the object is.

what is weight directly proportional to and measured w

The weight of an object and the mass of an object are directly proportional.

Weight is measured using a calibrated spring-balance (a newtonmeter).

balanced forces result

Balanced forces

• Equal size

• Opposite directions

• Resultant force = 0 N

The object:

• stays still, or

• continues moving at a constant speed in a straight line.

unbalanced forces result

Resultant force is not zero.

The object will:

• speed up,

• slow down, or

• change direction.

what does an isolated system have

An isolated system has no external forces acting on it.

what can a force acting at an angle be split into

A force acting at an angle can be split into:

• a horizontal component,

• a vertical component.

• These two components together have the same effect as the original force.

• usually done using scale drawings.

what happens when a force causes an object to move

When a force causes an object to move through a distance work is done on the object.

So a force does work on an object when the force causes a displacement of the object.

joule to Nm

1 joule = 1 newton-metre

What is the difference between elastic and inelastic deformation? State Hooke's Law.

Elastic deformation

• Object returns to its original shape.

Inelastic deformation

• Object is permanently changed.

Hooke's Law

• The extension of an elastic object is directly proportional to the force applied.

• This is only true up to the limit of proportionality.

relationship between work done and elastic potential energy

A force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring.

Provided the spring is not inelastically deformed, the work done on the spring and the elastic potential energy stored are equal.

What is a moment, and how can forces cause an object to rotate?

Force can cause an object to rotate (turn) about a pivot.

• Opening a door.

• Using a spanner to turn a nut.

• A seesaw rotating about its centre.

⭐ The turning effect of a force is called the moment of the force.

Key idea:

• The further from the pivot the force is applied, the greater the moment.

What is the principle of moments, and how do levers and gears work?

If an object is balanced,

Total clockwise moment = Total anticlockwise moment.

✅ Levers

• Increase the turning effect of a force.

• The further from the pivot you apply the force, the easier it is to turn the object.

✅ Gears

• Transmit rotational forces from one gear to another.

• They can change the size of the force and the speed of rotation.

what is a fluid and what it causes

A fluid can be either a liquid or a gas.

The pressure in fluids causes a force normal (at right angles) to any surface.

How does pressure change in a liquid? What is upthrust, and what affects floating and sinking?

Pressure increases with depth in a liquid.

• The deeper you go, the greater the pressure.

⭐ Upthrust

• A submerged object experiences greater pressure on the bottom than on the top.

• This creates an upward resultant force called upthrust.

Floating and sinking:

• If upthrust = weight → the object floats.

• If weight > upthrust → the object sinks.

Factors affecting floating and sinking:

• The weight of the object.

• The upthrust acting on it.

• The density of the liquid (denser liquids provide more upthrust).

What is atmospheric pressure, and why does it decrease with height?

✅ The atmosphere is a thin layer of air surrounding the Earth.

✅ Air molecules collide with surfaces, creating atmospheric pressure.

⭐ As height increases:

• There are fewer air molecules above you.

• The weight of the air above decreases.

• Therefore, atmospheric pressure decreases.

✅ The atmosphere also becomes less dense with increasing altitude.

what is displacement

Displacement includes both the distance an object moves, measured in a straight line from the start point to the finish point and the direction of that straight line.

Displacement is a vector quantity.

what is distance

how far an object moves and a scalar quality

What is speed?

✅ Speed is how fast an object moves.

⭐ Speed is a scalar quantity, which means it has magnitude only and no direction.

✅ The speed of a moving object is rarely constant.

what are some typical values of speed and what they depend on

Typical speeds:

• 🚶 Walking ≈ 1.5 m/s

• 🏃 Running ≈ 3 m/s

• 🚴 Cycling ≈ 6 m/s

• 🔊 Speed of sound in air ≈ 330 m/s

✅ A person's speed can depend on:

• Age

• Terrain

• Fitness

• Distance travelled

✅ The speed of sound and wind can also vary.

What is velocity, and what is the difference between vectors and scalars?

✅ Velocity is speed in a given direction.

⭐ A scalar quantity has magnitude only.

• Examples: speed and distance.

⭐ A vector quantity has magnitude and direction.

• Examples: velocity and displacement.

✅ An object moving in a circle can have a constant speed but a changing velocity because its direction is continuously changing.

what happens to an object falling through a fluid

An object falling through a fluid initially accelerates due to the force of gravity.

Eventually the resultant force will be zero and the object will move at its terminal velocity.

State Newton's First Law and explain inertia.

⭐ Newton's First Law:

If the resultant force acting on an object is zero, it will remain at rest or continue moving at a constant velocity.

✅ If resultant force = 0 N:

• A stationary object stays stationary.

• A moving object continues at the same speed and in the same direction.

✅ An object's velocity (speed and/or direction) only changes if there is a resultant force acting on it.

⭐ Inertia

• Inertia is the tendency of an object to remain at rest or continue moving with uniform motion.

state newtons second law

The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.

F = Ma

what is inertial mass

Inertial mass is a measure of how difficult it is to change the velocity of an object.

• The greater the inertial mass, the harder it is to accelerate or slow the object down.

M=F/a

newtons 3rd law

Whenever two objects interact, the forces they exert on each other are equal and opposite.

What is stopping distance, and how does speed affect it?

✅ Stopping distance is the total distance a vehicle travels before it stops.

Stopping distance = Thinking distance + Braking distance

⭐ Thinking distance

• The distance travelled during the driver's reaction time.

⭐ Braking distance

• The distance travelled while the brakes slow the vehicle down.

✅ For the same braking force, the greater the speed of the vehicle, the greater the stopping distance.

typical reaction time values and what affected by

Typical reaction time values range from 0.2 s to 0.9 s.

A driver’s reaction time can be affected by tiredness, drugs and alcohol. Distractions may also affect a driver’s ability to react.

How do brakes stop a vehicle, and why can large decelerations be dangerous?

✅ When brakes are applied, friction between the brakes and the wheels does work.

• The vehicle's kinetic energy decreases.

• The temperature of the brakes increases.

✅ The greater the speed of the vehicle, the greater the braking force needed to stop it in the same distance.

✅ The greater the braking force, the greater the deceleration.

⭐ Large decelerations can be dangerous because they may:

• Cause the brakes to overheat.

• Lead to loss of control of the vehicle.

when does a change in momentum occur

When a force acts on an object that is moving, or able to move, a change in momentum occurs.

What is the principle of conservation of momentum?

⭐ Conservation of momentum states that:

In a closed system, the total momentum before an event equals the total momentum after the event.

✅ This applies to events such as collisions and explosions.

✅ A closed system is one where no external forces act.

⭐ Momentum can be used to describe and explain what happens during a collision.

How do safety features reduce injury using the idea of rate of change of momentum?

In a crash or impact, an object’s momentum changes very quickly.

The force depends on how fast momentum changes:

Force = rate of change of momentum

🛑 Safety features work by increasing the time taken for the momentum to change:

• Seat belts stretch slightly → increase stopping time → reduce force.

• Air bags compress → increase time and distance of stopping → reduce force.

• Crash mats (gym) compress → slow down landing more gradually.

• Cycle helmets absorb impact → increase collision time and reduce force on the head.

• Cushioned playground surfaces reduce impact force by slowing the stop.🛑 Safety features work by increasing the time taken for the momentum to change:

What is the difference between transverse and longitudinal waves? How do we know waves transfer energy, not matter?

⭐ Transverse waves

• The vibration is perpendicular to the direction of energy transfer.

• Example: water ripples.

• They have crests and troughs.

⭐ Longitudinal waves

• The vibration is parallel to the direction of energy transfer.

• Example: sound waves in air.

• They have compressions and rarefactions.

🌊 Key difference:

• Transverse = vibrations at right angles

• Longitudinal = vibrations in the same direction

📡 Evidence that waves transfer energy, not matter:

• In water ripples, a floating object moves up and down, but does not travel with the wave.

• In sound waves, air particles vibrate back and forth, but do not move from speaker to ear.

What are amplitude, wavelength, frequency and period in waves?

⭐ Amplitude

• The maximum displacement of a point on a wave from its normal (undisturbed) position.

• Bigger amplitude = more energy in the wave.

⭐ Wavelength (λ)

• The distance between identical points on adjacent waves.

• Example: crest to crest or trough to trough.

⭐ Frequency (f)

• The number of waves passing a point each second.

• Unit: hertz (Hz).

⭐ Period (T)

• The time taken for one complete wave to pass a point.

what can waves be at a boundary

Waves can be reflected at the boundary between two different materials.

Waves can be absorbed or transmitted at the boundary between two different materials.

How do sound waves make us hear

⭐ Sound waves are vibrations that can travel through solids, liquids, and gases.

👂 How we hear sound:

• Sound waves travel through air into the ear.

• They make the eardrum vibrate.

• These vibrations are passed through tiny bones in the ear.

• The vibrations are then converted into electrical signals sent to the brain.

• The brain interprets them as sound.

why is human hearing limited in frequency?

🚫 Why hearing is limited:

• The ear only responds to a limited frequency range.

• Very low or very high frequencies do not make the ear structures vibrate effectively.

⭐ Human hearing range:

• 20 Hz to 20 kHz

How can waves be used to detect hidden structures, including ultrasound and seismic waves?

Waves can be used to detect objects or structures that cannot be seen directly by using reflection, absorption, and changes in speed.

🔊 Ultrasound waves

• Have a frequency above 20 kHz (so humans cannot hear them).

• Partially reflect when they meet a boundary between different materials.

• The time taken for echoes to return is used to calculate distance.

📌 Used in:

• Medical scans (e.g. checking a baby in the womb)

• Industrial testing (finding cracks in materials)

• Echo sounding (measuring sea depth or locating objects underwater)

🌍 Seismic waves (earthquakes)

• P-waves (longitudinal):

  • Travel through solids and liquids

  • Change speed depending on material

• S-waves (transverse):

  • Travel through solids only

  • Cannot travel through liquids

📌 What they tell us:

• By studying how P-waves and S-waves move through Earth, scientists discovered:

  • The Earth has a liquid outer core

  • The structure and size of the Earth's interior

What are electromagnetic waves and how do they transfer energy n example?

Electromagnetic waves (EM waves) are transverse waves that transfer energy from a source to an absorber.

🌈 Key properties:

• They form a continuous spectrum.

• All EM waves travel at the same speed in a vacuum (and air).

• They differ in wavelength and frequency.

📡 EM spectrum (long wavelength → short wavelength):

⚡ Energy transfer examples:

• Microwaves heat food in a microwave oven.

• Infrared is felt as heat from the Sun.

• Visible light allows us to see objects.

• X-rays pass through soft tissue to image bones.

How do electromagnetic waves interact with different materials, and why do they refract?

⭐ Different materials can absorb, transmit, reflect, or refract electromagnetic waves, and this often depends on the wavelength of the wave.

🌈 Key interactions:

• Absorption → wave energy is taken in by the material.

• Transmission → wave passes through the material.

• Reflection → wave bounces off a surface.

• Refraction → wave changes direction when entering a new medium.

🌊 Why refraction happens:

• Refraction occurs because waves change speed when they move between different materials.

• This change in speed causes the wave to bend at the boundary.

📐 Ray diagrams:

• Show the path of a wave.

• When a wave enters a new medium, the ray changes direction (bends).

• The amount of bending depends on how much the speed changes.

🌊 Wavefront idea :

• Wavefronts are lines showing the crests of waves.

• When a wave enters a new medium:

  • One side of the wave slows down first.

  • This causes the wavefront to pivot and change direction.

• This explains refraction in terms of different speeds across the wavefront.

millisieverts into sieverts

1000 millisieverts (mSv) = 1 sievert (Sv)

How are radio waves produced and absorbed, and why can some electromagnetic waves be dangerous?

⭐ Radio waves:

• Produced by oscillations in electrical circuits (alternating current).

• When absorbed, they can induce an alternating current in another circuit with the same frequency.

• This is how radio signals are transmitted and received.

⚛ Origin of EM waves:

• Electromagnetic waves are produced when there are changes in:

  • Electrons in atoms

  • Nuclei of atoms

• Gamma rays come from changes in the nucleus and have very high energy.

☢ Hazards of high-energy radiation:

• Ultraviolet, X-rays, and gamma rays can damage human tissue.

• The risk depends on:

  • Type of radiation (higher frequency = more energy)

  • Size of the dose

⭐ Radiation dose is measured in sieverts (Sv):

It measures the risk of harm to the body from radiation exposure.

Electromagnetic waves have many practical applications

📡 Radio waves

• Used for TV and radio

• Long wavelength → can travel long distances and through obstacles easily

📶 Microwaves

• Used for satellite communication and cooking food

• Can pass through the atmosphere → good for satellites

• Cause water molecules to vibrate → heat food

🔥 Infrared

• Used in heaters, cooking, and thermal imaging

• Easily absorbed by skin/materials → felt as heat

💡 Visible light

• Used in fibre optic communication

• Can travel through optical fibres by repeated reflection

☀ Ultraviolet

• Used in energy-efficient lamps and tanning

• High energy → can cause chemical reactions (e.g. fluorescence, skin tanning)

🩻 X-rays and gamma rays

• Used in medical imaging and cancer treatment

• Very high energy → can pass through body tissue or kill cells

how does a lens form an image in convex lenses and concave

A lens forms an image by refracting light.

In a convex lens, parallel rays of light are brought to a focus at the principal focus.

The distance from the lens to the principal focus is called the focal length.

Ray diagrams are used to show the formation of images by convex and concave lenses.

The image produced by a convex lens can be either real or virtual.

The image produced by a concave lens is always virtual.

types of reflections

Reflection from a smooth surface in a single direction is called specular reflection.

Reflection from a rough surface causes scattering: this is called diffuse reflection.

how do colour filters work, how r colours of opaque objects determined and what happens to all wavelengths (reflected, absorbed etc)

Colour filters work by absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour).

The colour of an opaque object is determined by which wavelengths of light are more strongly reflected.

Wavelengths that are not reflected are absorbed.

If all wavelengths are reflected equally the object appears white.

If all wavelengths are absorbed the objects appears black.

Objects that transmit light are either transparent or translucent.

what do all bodies do and what happens as temp increases

All bodies (objects), no matter what temperature, emit and absorb infrared radiation. The hotter the body, the more infrared radiation it radiates in a given time.

what is a perfect black body

A perfect black body is an object that absorbs all of the radiation incident on it. A black body does not reflect or transmit any radiation.

Since a good absorber is also a good emitter, a perfect black body would be the best possible emitter.

what determines whether a body heats up or stays constant, earths temp and examples?

Energy balance:

If a body is at constant temperature:

Energy absorbed = energy emitted

• If a body absorbs more radiation than it emits:
  → temperature increases

• If a body emits more than it absorbs:
  → temperature decreases

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🌍 Earth’s temperature depends on:

• Absorption of radiation from the Sun

• Emission of infrared radiation back into space

• Reflection of radiation (e.g. by clouds, ice, atmosphere)

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🌡 Everyday examples:

• A black shirt gets hotter than a white shirt because it absorbs more radiation.

• A cold drink warms up because it absorbs more heat radiation than it emits.

attraction and repulsion poles

The poles of a magnet are the places where the magnetic forces are strongest. When two magnets are brought close together they exert a force on each other.

Two like poles repel each other. Two unlike poles attract each other. Attraction and repulsion between two magnetic poles are examples of non-contact force.

what is a permanent magnet and an induced magnet

A permanent magnet produces its own magnetic field. An induced magnet is a material that becomes a magnet when it is placed in a magnetic field.

Induced magnetism always causes a force of attraction. When removed from the magnetic field an induced magnet loses most/all of its magnetism quickly.

What is a magnetic field and how can we describe its direction and strength?

A magnetic field is the region around a magnet where a force acts on other magnets or magnetic materials (iron, steel, cobalt, nickel).

🧲 Key facts:

• The force between a magnet and a magnetic material is always attractive.

• The magnetic field is strongest at the poles of a magnet.

• The field gets weaker with distance from the magnet.

🧭 Direction of a magnetic field:

• Defined as the direction of the force on a north pole placed in the field.

Field lines go from:

North pole → South pole

🌍 Earth’s magnetic field:

• The Earth acts like a large magnet.

• A compass needle is a small bar magnet.

• The needle aligns with the Earth’s magnetic field and points north.

what happens as a current flow through a conducting wire, how to increase strength

When a current flows through a conducting wire a magnetic field is produced around the wire.

The strength of the magnetic field depends on the current through the wire and the distance from the wire.

Shaping a wire to form a solenoid increases the strength of the magnetic field created by a current through the wire.

The magnetic field inside a solenoid is strong and uniform.

The magnetic field around a solenoid has a similar shape to that of a bar magnet.

Adding an iron core increases the strength of the magnetic field of a solenoid.

An electromagnet is a solenoid with an iron core.

What is the motor effect, Flemings left hand rule and factors affecting size of force?

When a conductor carrying a current is placed in a magnetic field the magnet producing the field and the conductor exert a force on each other.

✋ Fleming’s Left-Hand Rule:

Used to show the relationship between:

• Thumb → Force (motion)

• First finger → Magnetic field (N → S)

• Second finger → Current

Factors affecting the size of the force:

• Stronger magnetic field → bigger force

• Larger current → bigger force

• More wire in the field (longer conductor) → bigger force

How do electric motors work using the motor effect?

⭐ Electric motors:

• A coil of wire carrying a current is placed in a magnetic field.

• Forces act on opposite sides of the coil.

• These forces cause the coil to rotate.

• This rotation is the basis of an electric motor.

➡ The direction of rotation is shown using Fleming’s Left-Hand Rule.

⭐ Why the coil rotates:

• One side of the coil is pushed up, the other down.

• This creates a turning effect (moment).

• The coil keeps rotating continuously if the current is maintained.

how loudspeakers and headphones work

• A varying current flows through a coil in a magnetic field.

• The coil moves back and forth.

• This makes a cone vibrate, producing pressure waves in air (sound).

What is electromagnetic induction (generator effect) and what affects the induced current?

⭐ Electromagnetic induction (generator effect) happens when:

• A conductor moves in a magnetic field, or

• The magnetic field around a conductor changes

➡ This causes a potential difference (voltage) to be induced across the conductor.

• If the circuit is complete → an induced current flows.

Movement or changing magnetic field → induced p.d. → induced current

📏 Factors affecting induced current / voltage:

• Speed of movement (faster → bigger induced p.d.)

• Strength of magnetic field (stronger → bigger induced p.d.)

• Length of conductor in field (more wire → bigger effect)

• Number of turns in coil (more turns → bigger induced p.d.)

🔄 Direction of induced current:

• Depends on:

  • direction of movement

  • direction of magnetic field

• Can be worked out using Fleming’s right-hand rule (generators)

what’s Lenz’s law

• The induced current creates its own magnetic field

• This field opposes the change that caused it
  (e.g. opposes motion or change in field)

How does an alternator produce AC?

⭐ A coil rotates in a magnetic field (generator effect).

• Uses slip rings

• As the coil rotates, the induced voltage changes direction every half turn

➡ Output = alternating current (AC)

• Voltage graph = wave that goes positive and negative

what is hookes law

applied force is directly proportional to the objects extension up to a limit of proportionality

How does a dynamo produce DC?

⭐ A coil rotates in a magnetic field (generator effect).

• Uses a split-ring commutator

• This reverses connections every half turn so current flows in one direction only

➡ Output = direct current (DC)

• Voltage graph = pulsing but always above (or below) zero

What does the voltage–time graph of AC look like?

• Smooth wave pattern

• Alternates between positive and negative values

• Shows current repeatedly changing direction

What does the voltage–time graph of DC from a dynamo look like?

• Pulses in one direction only

• Never goes negative

• Still varies in size but does not reverse direction

How does a moving-coil microphone work?

⭐ Sound waves cause a diaphragm to vibrate.

• The diaphragm is attached to a coil of wire.

• The coil moves in a magnetic field.

➡ This movement induces a varying potential difference (voltage) (generator effect).

What is the generator effect in a microphone?

⭐ When a coil moves in a magnetic field, a voltage is induced.

• Sound waves make the coil move back and forth.

• This creates a changing electrical signal.

What is sound converted into in a microphone?

⭐ Sound waves (pressure variations in air) are converted into:
➡ Electrical signals (varying current/voltage)

What is a transformer?

⭐ A transformer has:

• A primary coil

• A secondary coil

• Both wrapped around an iron core

➡ Iron is used because it is easily magnetised, helping transfer the magnetic field between coils.

What does a transformer do?

⭐ A transformer uses changing current in the primary coil to induce a voltage in the secondary coil (electromagnetic induction).

➡ It can:

• Increase voltage (step-up)

• Decrease voltage (step-down)

Why do transformers need AC?

⭐ Transformers only work with alternating current because:

• The current must be changing to create a changing magnetic field

• This induces a current in the secondary coil

➡ DC does not work properly in a transformer.