AQA GCSEs physics

Why do we keep the same person dropping the ruler?

Each person can have a different reaction time so we have to keep this factor the same

Why is it important that we drop the ruler without warning?

It would give the person catching the ruler an unfair advantage and reduce their reaction time

What is the value of acceleration due to gravity?

9.8 m/s2 (can also say the units are N/kg)

Why do we repeat an investigation?

So we can identify any anomalies and calculate a mean.

Describe breaking forces

When brakes are pressed, brake pads cause friction on the wheels. We say that work is done on the wheels which means that energy is transferred from the thermal store of the car to the kinetic store of the brakes. This makes the brakes get hot.

Faster vehicles need to transfer more energy from the kinetic store which can be dangerous. Brakes can overheat so they don’t work properly and the car might skid

What is momentum?

Momentum is a measurement of mass in motion: how much mass is in how much motion.

What is the momentum of an object which is not moving?

What is meant by the term ‘conservation of momentum’?

Why is momentum classed as a vector?

Zero

In a closed system, the momentum before an event/collision, is the same as the momentum after an event/collision.

It has both a magnitude (size) AND a direction.

What is the difference between the directions of their momentums before the collision?

What does it mean when we say that momentum is a vector?

Edgar’s momentum is to the right (in the positive direction), Manuel’s direction is to the left (in the negative direction)

Momentum has both a magnitude (size) and a direction.

Explaining momentum - The skateboard moves backwards as the skateboarder jumps forwards. Explain, using the idea of momentum, why the skateboard moves backwards.

This is because momentum is conserved, so the momentum before is zero and the momentum after is also zero.

After jumping, the skateboarder has forwards momentum.

Therefore the skateboard has equal momentum, but acting in the backwards direction: this is why the skateboard moves backwards.

explaining momentum - The bumper cars crash into each other and stop. Explain why both bumper cars stop after the crash.

The total momentum is zero after the collision because the bumper cars are stationary

As momentum is conserved, this means the momentum of the bumper cars was zero before the collision

This happens because the momentum of each bumper car before the collision was equal in magnitude (size) but opposite in direction.

What is a ‘medium’?

What is ‘matter’?

Give an example from everyday life which demonstrates the idea that waves transfer energy, but not matter?

Describe the movement of vibrations in a transverse wave

The material which the wave is travelling through

The stuff that makes up a substance

If you drop a twig in the water, the ripples spread out, but they don’t carry the water or the twig away with them

The vibrations are at right angles (perpendicular) to the direction of the wave movement/energy transfer

Describe the movement of vibrations in a longitudinal wave

Give examples of both type of wave

The vibrations are in the same direction as the direction of the wave movement/energy transfer

Transverse: light, ripples on water, waves on a string, all electromagnetic waves

Longitudinal: sound

What is meant by the amplitude of a wave?

What is meant by the wavelength of a wave?

What is meant by the frequency of a wave?

What units are used for frequency?

What is meant by the ‘period’ of a wave?

What units are used for the period?

The maximum displacement of the wave from the rest position. Measured in metres

The distance between one point on a wave and the same point on the next wave. Measured in metres

The number of waves passing a point in one second

hertz, Hz.

The time it takes for one wave to pass a point

seconds, s

MEASURING SPEED OF SOUND PRACTICAL Use the diagram to describe how 2 students are able to use this method to calculate the speed of sound.

Student A claps the pieces of wood together at the same time that student B starts the stopwatch

Student B stops the stopwatch when they hear the echo

The distance between the students and the wall is measured and multiplied by 2 (as the sound has travelled to the wall, then back again)

Use the equation: speed = distance ÷ time and calculate the speed of the sound

Measuring Speed of Sound follow up questions

What equipment will they need?

Why is this experiment not very accurate?

Pieces of wood to bang together, stop clock and tape measure

The times being measured are very short, so any inaccurate measurements have a big effect

Investigating Waves in solids - questions

Why do we use the signal generator?

What is the frequency of the wave?

How can you measure the wavelength of a wave accurately

How can you calculate the speed of the wave?

To set the frequency of the vibrations

The number of waves passing a point in a second

Count how many complete wavelengths are on the string. Measure the length of the whole string and divide by the number of wavelengths

Use the equation v = f λ to find the speed. The number for the frequency is the number that the signal generator is set to, and the number of wavelengths can be measured (see Q3).

INVESTIGATING WAVES IN LIQUIDS - Questions

How do we work out the frequency of the waves?

How can you measure the wavelength of a wave accurately

How can you calculate the speed of the wave?

Count the number of ripples that pass a point in 10 seconds then divide by 10 (number of waves per second = frequency)

Measure the distance across 10 gaps between the shadow lines. Divide this number by 10 to find the average wavelength. To make this easier, it can be easier to take a photograph

Use the equation v = f λ to find the speed.

what are the three things that can happen when a wave meets a boundary

• waves can be absorbed

• transmitted

• reflected

• WHAT IS REFRACTION?

Describe what happens in reflection?

• When a wave crosses a boundary between two materials, it can change direction.

A line can be drawn at 90° to the boundary. This is called the normal. If the wave hits the boundary after travelling along the normal, it is not refracted, but if it hits the boundary at an angle, it will be. The incident ray is the ray coming into a boundary and the refracted ray is the ray leaving it .The angle of incidence is the angle between the incident ray and the normal. The angle of refraction is the angle between the refracted ray and the normal

REFLECTION QUESTIONS

Explain what happens to the speed of a wave when it passes from the air into a glass block.

Explain what happens to the speed of a wave when it passes from a glass block into the air.

Describe what happens to the path of a wave as it enters a more dense medium at an angle.

Describe what happens to the path of a wave as it enters a less dense medium at an angle.

Describe what happens to the speed and the direction of a wave which enters a more dense material along the normal.

What happens to the wavelength of a wave when it is refracted?

What happens to the frequency of a wave when it is refracted?

The wave slows down because the glass block is more dense than the air.

The wave speeds up because the air is less dense than the glass block.

The wave will refract (bend) towards the normal.

The wave will refract (bend) away from the normal.

The speed of the wave decreases, but the angle does not change.

It changes (if the wave slows down, the wavelength decreases, and vice versa)

It remains the same.

DESCRIBE WAVE FRONT DIAGRAMS e.g 1

If a wave passes from a less dense material into a more dense material, it will slow down. This means the wavelength will decrease On the diagram, the wave fronts should be drawn closer together

WAVE FRONT DIAGRAMS e.g 2

If a wave passes from a more dense material into a less dense material, it will sped up This means the wavelength will increase. On the diagram, the wave fronts should be drawn further apart

Wave front diagrams e.g

When a wave crosses a boundary at an angle, only part of the wave front crosses at first. If a wave passes from a less dense material into a more dense material, the part that crosses first will travel slower than the rest of the wave front. By the time the whole wave crosses the boundary, the faster part of the wave front will have travelled further than the slower part. This difference in the distance travelled makes the wave refract. Because the wave has slowed down, the wave fronts have moved closer together

WAVE FRONT DIAGRAM e.g 4

When a wave crosses a boundary at an angle, only part of the wave front crosses at first. If a wave passes from a more dense material into a less dense material, the part that crosses first will travel faster than the rest of the wave front. By the time the whole wave crosses the boundary, the faster part of the wave front will have travelled further than the slower part. This difference in the distance travelled makes the wave refract. Because the wave has sped up, the wave fronts have moved further apart

Electromagnetic Spectrum

What type of waves are electromagnetic waves?

What do all electromagnetic waves have in common?

What is different about each part of the electromagnetic spectrum?

Describe the 2 changes in atoms which can make electromagnetic waves be absorbed or emitted

Which part of the EM spectrum has the longest wavelength?

Which part of the EM spectrum has the shortest wavelength?

Which part of the EM spectrum has the highest frequency?

Which part of the EM spectrum has the lowest frequency?

Transverse

They travel at the same speed in a vacuum

They all have different frequencies and wavelength

Electrons can move between energy levels. Changes in the nucleus can also take place.

Radio waves

Gamma rays

Gamma rays

Radio waves

DESCRIBE THE USES OF THE ELECTROMAGNETIC WAVES:

• radiowaves

• microwaves

• infrared

• visible light

radiowaves -

• communication: radio and TV signals

microwaves -

• communication: satellite TV and mobile phones

• Cooking food - water in the food absorbs energy from the microwaves and heats the food up

infrared -

• Infrared cameras detect IR radiation and create a picture - thermal imaging is used by police

• IR radiation heats things up (eg an electric heater) and can be used to cook food

visible light -

• Used to carry data over long distances in optical fibres

DESCRIBE THE USES OF THE ELECTROMAGNETIC WAVES:

• ultraviolet

• x-rays

• gamma

USES

ultraviolet

• Security pens can be used to invisibly mark possessions. The ink will glow under UV light to the police can track property.

• UV lamps can be used for tanning on sunbeds

x-rays

• Used to create x-ray images to check for broken bones.

• Can be used to treat cancer by killing cancer cells

Gamma

• Used to sterilise medical equipment as the rays will kill the bacteria

• Can be used to treat cancer by killing cancer cells

• Used as medical tracers in the body as they can be tracked as they move around the body.

DESCRIBE THE DANGERS OF THE ELECTROMAGNETIC WAVES:

radiowaves

microwaves

infrared

visible light

radiowaves - none

microwaves- none

infrared - Low danger -Can cause skin burns

visible light - Low danger

DESCRIBE THE DANGERS OF THE ELECTROMAGNETIC WAVES:

ultraviolet

x-rays

gamma

ultraviolet

• Damages surface cells of the body causing sunburn and skin aging.

• Can also cause blindness and skin cancer

x-rays

• Ionising radiation which can destroy cells and damage genes.This can cause cancer.

Gamma

• same as x-rays - Ionising radiation which can destroy cells and damage genes.This can cause cancer.

Explain how electrical signals in the transmitter produce a signal in the receiver. (radio waves)

An alternating electrical current flows in the transmitter. Electrons oscillate (vibrate) at the same frequency as the A.C. This produces radio waves which are absorbed by the receiver. This causes electrons in the receiver (aerial) to oscillate and produce an alternating current with the same frequency as both the radio wave and the current in the transmitter.

Electromagnetic Spectrum

Why are longer wavelength radio waves used for international radio stations?

Why are shorter wavelength radio waves also used for radio transmission?

Why are microwaves used to heat up food? (Talk about water molecules in your answer).

Why are microwaves suitable for satellite communication?

Describe the changes in energy stores when an object absorbs infrared radiation. What effect will this have on the object’s temperature?

They can diffract around the curved surface of the Earth.

They are reflected from the ionosphere

Microwaves transfer energy to the food and water molecules easily absorb this energy. The energy is transferred to the food via the heating pathway.

Microwaves can pass through the atmosphere easily to reach the satellites in space.

Energy is transferred into the thermal store of the object from the radiation pathway. The object will heat up.

Electromagnetic Spectrum

How can visible light be used to transmit information?

Why is visible light suitable for transmission in this way?

How do UV security pens work?

Why are x-rays suitable for looking at broken bones?

The light rays are reflected back and forth along the optical fibre from one end to the other.

It is easy to reflect light enough that it remains inside a narrow fibre. Light in not easily absorbed or scattered as it travels along the fibre.

Property can be invisibly marked. If stolen property is found, the police will shine UV light in it and any ink from the security pen will glow. This means property can be returned to owners.

They can pass through flesh but not through bone

Electromagnetic Spectrum

How can x-rays and gamma rays be used to treat cancer?

What is a ‘medical tracer’?

Why is gamma radiation suitable for use as a medical tracer?

Why are sunbeds dangerous?

What does ionising radiation do to atoms?

They can kill cells. They are aimed at cancer cells to kill them

A radioactive substance is put into the body which will give out radiation. This radiation can be detected on the outside, so it is possible to see how the substance is moving around the body

It can pass out of the body to be detected on the outside.

They give out UV radiation which is a type of ionising radiation. It can cause skin cancer.

When the radiation hits the atom, it can make the atom lose or gain electrons.

Electromagnetic Spectrum

What are the 3 types of ionising radiation?

What is the link between the frequency of a wave and the damage that it causes?

UV light, x-rays and gamma rays

The higher frequency that a wave has, the more energy it has, so it can do the most damage. This means that gamma rays are the most damaging.

What is radiation dose?

Explain why a radiographer wears a lead apron and leaves the room when taking x rays.

It is a measure of the risk of harm of being exposed to some radiation. (It is measured in sieverts (Sv))

The radiographer takes multiple x rays a day and could be exposed to a high dose, giving a higher risk of cancer. The lead apron and walls will absorb the radiation, reducing the dose.

Investigating Infrared Radiation questions

What is a Leslie cube?

Why do we use a cap?

Why might we use a heat proof mat?

Why do we make sure we measure it at the same distance?

Which side was the best emitter of infrared?

Which material was the best absorber of infrared?

Which material is the worst absorber of infrared?

A metal cube that can be filled with hot water

To reduce heat loss by convection through the air

To prevent heat loss by conduction through the table

To make sure our experiment is a fair test and nothing other than the type of surface is affecting the results

Matte black materials

Matte black materials

The shiny material

DESCRIBE MAGNETS

All magnets have a north and a south pole. Magnets put a non-contact force on each other. This means that they do not have to touch . Two of the same poles will repel each other, whereas different poles will attract There are 3 metals which are magnetic. These are iron, cobalt and nickel. The area around a magnet is called the magnetic field

DESCRIBE DRAWING FIELD LINES - magnets

The direction of the lines go FROM north TOWARDS south. When lines are close together it means the magnetic field is strong. The magnetic field is strongest at the poles Field line must not touch or cross

name the two types of magnets

permanent and induced

Right Hand Grip Rule QUESTIONS

Describe how to use the right hand grip rule.

What happens when a current flows through a wire?

How can you see this effect?

What shape is the field around a wire?

What happens if you reverse the direction of the current?

Where is the magnetic field the strongest?

Point your thumb in the direction of the current. Curl your fingers. The direction of your fingers is the direction of the field

A magnetic field forms around the wire

Place a compass close to the wire

Circles around the wire

you reverse direction of the magnetic field

Closest to the wire

ELECTROMAGNETS QUESTIONS

What is a solenoid?

Describe the magnetic field inside a solenoid

How can we turn a solenoid into an electromagnet?

How do we increase the strength of a solenoid?

A coil of wire

Strong and uniform

Add an iron core

More coils of wire, add an iron core or increase the current through the wire

THE MOTOR EFFECT

How does this situation cause the wire to move?

When is the force zero?

Describe the direction in which the force on the wire acts.

How can we make the force stronger?

When a wire carrying current is put between the poles of a magnet, the magnetic field around the wire interacts with the magnetic field of the magnet. The wire and the magnet will exert a force on each other which causes the wire to move.

When the wire is parallel to the magnetic field

The force acts at right angles to the magnetic field and the direction of the current.

A stronger magnet will give more force. The force also increases if more current passes through the wire.

Fleming’s Left Hand Rule

What do we use Fleming’s Left Hand Rule for?

Write a method to use Fleming’s Left Hand Rule.

We use fleming’s left-hand rule to work out the direction of the force which causes the motion.

• Use your left hand

• Place thumb and first two fingers at right angles to each other

• Point your First finger in the direction of the Field

• Point your seCond finger in the direction of the Current

• Your thuMb points in the direction of the Motion (caused by a FORCE)

Fleming’s Left Hand Rule

What happens if the direction of either the current or the field is reversed?

What happens if they are both reversed?

The direction of the force will also be reversed.

The direction of the force will stay in the original direction.

D.C. Electrical Motors - Explaining how they work

• As the current flows through the coil, a magnetic field is produced around the wire. This field interacts with the magnetic field of the permanent magnets and a force acts on the coil.

• The force will act upwards along one side of the coil, and downwards along the other side.

• These opposite forces cause the coil to rotate on the spindle.

• the split ring commutator reverses the direction of the current every half turn, which keeps the forces acting the same way so the coil keeps spinning.