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AQA Additional Science. Physics 2. A slideshow that covers the entire AQA 2006 Syllabus Physics 2 Module. W Richards. Distance, Speed and Time. Speed = distance (in metres) time (in seconds). D. S. T. Seb walks 200 metres in 40 seconds. What is his speed?

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Aqa additional science

AQA Additional Science

Physics 2

A slideshow that covers the entire AQA 2006 Syllabus Physics 2 Module

W Richards


Distance speed and time

Distance, Speed and Time

Speed = distance (in metres)

time (in seconds)

D

S

T

  • Seb walks 200 metres in 40 seconds. What is his speed?

  • Lucy covers 2km in 1,000 seconds. What is her speed?

  • How long would it take Freddie to run 100 metres if he runs at 10m/s?

  • Sue travels at 50m/s for 20s. How far does he go?

  • Hannah drives her car at 85mph (about 40m/s). How long does it take her to drive 20km?


Speed vs velocity

Speed vs. Velocity

This car is travelling at a speed of 20m/s

This car is travelling at a velocity of 20m/s east

Speed is simply how fast you are travelling…

Velocity is “speed in a given direction” (a “vector quantity”)…


Acceleration

Acceleration

V-U

Acceleration = change in velocity (in m/s)

(in m/s2) time taken (in s)

A

T

  • A cyclist accelerates from 0 to 10m/s in 5 seconds. What is her acceleration?

  • A ball is dropped and accelerates downwards at a rate of 10m/s2 for 12 seconds. How much will the ball’s velocity increase by?

  • A car accelerates from 10 to 20m/s with an acceleration of 2m/s2. How long did this take?

  • A rocket accelerates from 1,000m/s to 5,000m/s in 2 seconds. What is its acceleration?


Velocity time graphs

Velocity-time graphs

  • 1) Upwards line =

  • 4) Downward line =

  • 2) Horizontal line =

  • 3) Upwards line =

80

60

40

20

0

Velocity

m/s

T/s

10 20 30 4050


Aqa additional science

80

60

40

20

0

Velocity

m/s

T/s

10 20 30 4050

  • How fast was the object going after 10 seconds?

  • What is the acceleration from 20 to 30 seconds?

  • What was the deceleration from 30 to 50s?

  • How far did the object travel altogether?


Balanced and unbalanced forces

Balanced and unbalanced forces

Reaction

Consider a camel standing on a road. What forces are acting on it?

These two forces would be equal – we say that they are BALANCED. The camel doesn’t move anywhere.

Weight


Balanced and unbalanced forces1

Balanced and unbalanced forces

Reaction

What would happen if we took the road away?

The camel’s weight is no longer balanced by anything, so the camel falls downwards…

Weight


Introduction to forces

Introduction to Forces

A force is a “push” or a “pull”. Some common examples:

Air resistance/drag – a contact force that acts against anything moving through air or liquid

Weight (mg) – pulls things towards the centre of the Earth

_____ – a contact force that acts against anything moving

Upthrust – keeps things afloat


Air resistance

Air Resistance

Air resistance is a force that opposes motion through air. The quicker you travel, the bigger the air resistance:

The same applies to a body falling through a liquid (called “drag” or “upthrust”).


Balanced and unbalanced forces2

Balanced and unbalanced forces


Balanced and unbalanced forces3

Balanced and unbalanced forces

1) This animal is either ________ or moving with _____ _____…

2) This animal is getting _________…

3) This animal is getting _______….

4) This animal is…


Resultant force

Resultant Force

Calculate the resultant force of the following:

500N

100N

700N

600N

50N

700N

700N

800N

800N

200N

100N


Force and acceleration

Force and acceleration

F

M

A

If the forces acting on an object are unbalanced then the object will accelerate, like these wrestlers:

Force (in N) = Mass (in kg) x Acceleration (in m/s2)


Force mass and acceleration

Force, mass and acceleration

F

M

A

  • A force of 1000N is applied to push a mass of 500kg. How quickly does it accelerate?

  • A force of 3000N acts on a car to make it accelerate by 1.5m/s2. How heavy is the car?

  • A car accelerates at a rate of 5m/s2. If it weighs 500kg how much driving force is the engine applying?

  • A force of 10N is applied by a boy while lifting a 20kg mass. How much does it accelerate by?


Terminal velocity

Terminal Velocity

Consider a skydiver:

  • At the start of his jump the air resistance is _______ so he _______ downwards.

2) As his speed increases his air resistance will _______

3) Eventually the air resistance will be big enough to _______ the skydiver’s weight. At this point the forces are balanced so his speed becomes ________ - this is called TERMINAL VELOCITY

Words – increase, small, constant, balance, accelerates


Terminal velocity1

Terminal Velocity

Consider a skydiver:

  • 4) When he opens his parachute the air resistance suddenly ________, causing him to start _____ ____.

5) Because he is slowing down his air resistance will _______ again until it balances his _________. The skydiver has now reached a new, lower ________ _______.

Words – slowing down, decrease, increases, terminal velocity, weight


Velocity time graph for terminal velocity

Velocity-time graph for terminal velocity…

Parachute opens – diver slows down

Speed increases…

Terminal velocity reached…

On the Moon

New, lower terminal velocity reached

Diver hits the ground

Velocity

Time


Stopping a car

Stopping a car…

Thinking distance

(reaction time)

Braking distance

Tiredness

Too much alcohol

Too many drugs

Poor visibility

Wet roads

Icy roads

Tyres/brakes worn out

Driving too fast


Momentum

Momentum

Momentum = Mass x Velocity

P

(in kgms-1)(in kg)(in ms-1)

M

V

Any object that has both mass and velocity has MOMENTUM. Momentum (symbol “p”) is simply given by the formula:

  • What is the momentum of the following?

  • A 1kg football travelling at 10ms-1

  • A 1000kg Ford Capri travelling at 30ms-1

  • A 20g pen being thrown across the room at 5ms-1

  • A 70kg bungi-jumper falling at 40ms-1


Force and momentum

Force and momentum

mv

Force = Change in momentum

(in kgm/s)

(in N)

Time

(in s)

F

T

Also called “impulse”

Newton’s second law of motion says that the force acting on an object is that object’s rate of change of momentum. In other words…

  • For example, David Beckham takes a free kick by kicking a stationary football with a force of 40N. If the ball has a mass of 0.5kg and his foot is in contact with the ball for 0.1s calculate:

  • The change in momentum of the ball (its impulse),

  • The speed the ball moves away with


Example questions

Example questions

  • Ben likes playing golf. He strikes a golf ball with a force of 80N. If the ball has a mass of 200g and the club is in contact with it for 0.2s calculate a) the change in momentum of the golf ball, b) its speed.

  • Nick thinks it’s funny to hit tennis balls at Tom. He strikes a serve with a force of 30N. If the ball has a mass of 250g and the racket is in contact with it for 0.15s calculate the ball’s change in momentum and its speed.

  • Dan takes a dropkick by kicking a 0.4kg rugby ball away at 10m/s. If his foot was in contact with the ball for 0.1 seconds calculate the force he applied to the ball.

  • Simon strikes a 200g golf ball away at 50m/s. If he applied a force of 50N calculate how long his club was in contact with the ball for.


Safety features

Safety features

mv

F

T

Let’s use Newton’s Second Law to explain how airbags work:

  • Basically:

  • The change in momentum is the same with or without an airbag

  • But having an airbag increases the time of the collision

  • Therefore the force is reduced


Weight vs mass

Weight vs. Mass

W

M

g

Earth’s Gravitational Field Strength is 10N/kg. In other words, a 1kg mass is pulled downwards by a force of 10N.

Weight = Mass x Gravitational Field Strength

(in N) (in kg) (in N/kg)

  • What is the weight on Earth of a book with mass 2kg?

  • What is the weight on Earth of an apple with mass 100g?

  • Dave weighs 700N. What is his mass?

  • On the moon the gravitational field strength is 1.6N/kg. What will Dave weigh if he stands on the moon?


Stopping a car1

Stopping a car…

Thinking distance

(reaction time)

Braking distance

Tiredness

Too much alcohol

Too many drugs

Poor visibility

Wet roads

Icy roads

Tyres/brakes worn out

Driving too fast


Work done

Work done

W

F

D

When any object is moved around work will need to be done on it to get it to move (obviously).

We can work out the amount of work done in moving an object using the formula:

Work done=Forcexdistance moved

in J in N in m


Example questions1

Example questions

  • Bori pushes a book 5m along the table with a force of 5N. He gets tired and decides to call it a day. How much work did he do?

  • Alicia lifts a laptop 2m into the air with a force of 10N. How much work does she do?

  • Martin does 200J of work by pushing a wheelbarrow with a force of 50N. How far did he push it?

  • Chris cuddles his cat and lifts it 1.5m in the air. If he did 75J of work how much force did he use?

  • Carl drives his car 1000m. If the engine was producing a driving force of 2000N how much work did the car do?


Elastic potential energy

Elastic Potential Energy

Elastic potential energy is the energy stored in a system when work is done to change its shape, e.g:


Kinetic energy

Kinetic energy

Any object that moves will have kinetic energy.

The amount of kinetic energy an object has can be found using the formula:

Kinetic energy = ½ x mass x velocity squared

in J in kg in m/s

KE = ½ mv2


Example questions2

Example questions

  • Nicole drives her car at a speed of 30m/s. If the combined mass of her and the car is 1000kg what is her kinetic energy?

  • Shanie rides her bike at a speed of 10m/s. If the combined mass of Shanie and her bike is 80kg what is her kinetic energy?

  • Dan is running and has a kinetic energy of 750J. If his mass is 60kg how fast is he running?

  • George is walking to town. If he has a kinetic energy of 150J and he’s walking at a pace of 2m/s what is his mass?


Random questions

Random questions…

  • Sophie tries to run 100m in 12 seconds and succeeds. How fast did she run?

  • Tommy accelerates at a rate of 2m/s2 for 3 seconds. If he started at 10m/s what was his final speed?

  • Charlie decides to lift his book up into the air. His book has a mass of 100g and he lifts it 50cm. Calculate the work done.

  • Lewis accelerates from 0 to 10m/s in 5 seconds. If his mass is 70kg how much force did his legs apply?

  • Rachel rides 1km at a speed of 20m/s. How long did the journey take?

  • Claire thinks it’s funny to push James with a force of 120N. If James has a mass of 60kg calculate his acceleration.

  • Lauren slams on the brakes on her bike and her brakes do 20,000J of work. If the combined mass is 100kg what speed was she travelling at?

  • Tom has a mass of 75kg. If he accelerates from 10 to 20m/s in 2s how much force did he apply?


Random questions1

Random questions…

  • Georgina amuses herself by throwing things at Sarah. If she throws a ball with a speed of 20m/s and the distance between her and Sarah is 5m how long will it take to reach her?

  • Mr Richards throws calculators around the room with a force of 20N. If each calculator has a mass of 200g calculate the acceleration.

  • Sam has a mass of 70kg. What is his weight on Earth, where the gravitational field strength is 10N/kg?

  • Zak does some work by pushing a box around with a force of 1N. He does 5J of work and decides to call it a day. How far did he push it?

  • On the moon Matt might weigh 112N. If the gravitational field strength on the moon is 1.6N/kg what is his mass? What will he weigh on Earth?

  • Dan likes bird watching. He sees a bird fly 100m in 20s. How fast was it flying?

  • How much kinetic energy would Richard have if he travelled at a speed of 5m/s and has a mass of 70kg?


Momentum1

Momentum

Momentum = Mass x Velocity

P

(in kgms-1)(in kg)(in ms-1)

M

V

Any object that has both mass and velocity has MOMENTUM. Momentum (symbol “p”) is simply given by the formula:

  • What is the momentum of the following?

  • A 1kg football travelling at 10ms-1

  • A 1000kg Ford Capri travelling at 30ms-1

  • A 20g pen being thrown across the room at 5ms-1

  • A 70kg bungi-jumper falling at 40ms-1


Conservation of momentum

Conservation of Momentum

Speed = 50ms-1

Speed = 20ms-1

Speed = ??ms-1

In any collision or explosion momentum is conserved (provided that there are no external forces have an effect). Example question:

Two cars are racing around the M25. Car A collides with the back of car B and the cars stick together. What speed do they move at after the collision?

Mass = 1000kg

Mass = 800kg

Mass = 1800kg

Momentum before = momentum after…

…so 1000 x 50 + 800 x 20 = 1800 x V…

…V = 36.7ms-1


Momentum in different directions

Momentum in different directions

Speed = 20ms-1

Mass = 1000kg

Mass = 800kg

Speed = 50ms-1

What happens if the bodies are moving in opposite directions?

Momentum is a VECTOR quantity, so the momentum of the second car is negative…

Total momentum = 1000 x 50 – 800 x 20 = 34000 kgms-1

Speed after collision = 34000 kgms-1 / 1800 = 18.9ms-1


Another example

Another example

α

241

237

Am

Np

4

95

93

2

Consider the nuclear decay of Americium-241:

If the new neptunium atom moves away at a speed of 5x105 ms-1 what was the speed of the alpha particle?


More questions

More questions…

  • A white snooker ball moving at 5m/s strikes a red ball and pots it. Both balls have a mass of 1kg. If the white ball continued in the same direction at 2m/s what was the velocity of the red ball?

  • A car of mass 1000kg heading up the M1 at 50m/s collides with a stationary truck of mass 8000kg and sticks to it. What velocity does the wreckage move forward at?

  • A defender running away from a goalkeeper at 5m/s is hit in the back of his head by the goal kick. The ball stops dead and the player’s speed increases to 5.5m/s. If the ball had a mass of 500g and the player had a mass of 70kg how fast was the ball moving?

  • A gun has a recoil speed of 2m/s when firing. If the gun has a mass of 2kg and the bullet has a mass of 10g what speed does the bullet come out at?


Force and momentum1

Force and momentum

mv

Force = Change in momentum

(in kgm/s)

(in N)

Time

(in s)

F

T

Also called “impulse”

Newton’s second law of motion says that the force acting on an object is that object’s rate of change of momentum. In other words…

  • For example, David Beckham takes a free kick by kicking a stationary football with a force of 40N. If the ball has a mass of 0.5kg and his foot is in contact with the ball for 0.1s calculate:

  • The change in momentum of the ball (its impulse),

  • The speed the ball moves away with


Example questions3

Example questions

  • Ben likes playing golf. He strikes a golf ball with a force of 80N. If the ball has a mass of 200g and the club is in contact with it for 0.2s calculate a) the change in momentum of the golf ball, b) its speed.

  • Nick thinks it’s funny to hit tennis balls at Tom. He strikes a serve with a force of 30N. If the ball has a mass of 250g and the racket is in contact with it for 0.15s calculate the ball’s change in momentum and its speed.

  • Dan takes a dropkick by kicking a 0.4kg rugby ball away at 10m/s. If his foot was in contact with the ball for 0.1 seconds calculate the force he applied to the ball.

  • Simon strikes a 200g golf ball away at 50m/s. If he applied a force of 50N calculate how long his club was in contact with the ball for.


Safety features1

Safety features

mv

F

T

Let’s use Newton’s Second Law to explain how airbags work:

  • Basically:

  • The change in momentum is the same with or without an airbag

  • But having an airbag increases the time of the collision

  • Therefore the force is reduced


Static electricity

Static Electricity

+

-

-

+

Static electricity is when charge “builds up” on an object and then stays “static”. How the charge builds up depends on what materials are used:

+

+

-

-

+

+

+

-

-

-

+

+

-

+

-

-


Static electricity1

Static Electricity

-

-

+

-

-

+

+

-

-

-

-

-


Van de graaf generators

Van de Graaf generators


Uses of static smoke precipitators

Uses of Static – Smoke Precipitators

Chimney

Negatively charged plates

-

-

-

-

-

-

Positively charged grid

+

+

+


Uses and dangers of static electricity

Uses and dangers of Static Electricity

Find out how static electricity is used in the following:

1) Photocopiers

2) Paint sprayer

Find out how static electricity is dangerous in the following situations:

1) Fuel pipes

2) Hospitals


Circuit symbols

Circuit Symbols

Variable resistor

A

V

Diode

Switch

Bulb

Ammeter

Voltmeter

LDR

Resistor

Cell

Fuse

Thermistor

Battery


Electric current

Electric Current

Note that electrons go from negative to positive

+

-

e-

e-

Electric current is a flow of negatively charged particles (i.e. electrons).

By definition, current is “the rate of flow of charge”


Basic ideas

Basic ideas…

Electric current is when electrons start to flow around a circuit. We use an _________ to measure it and it is measured in ____.

Potential difference (also called _______) is how big the push on the electrons is. We use a ________ to measure it and it is measured in ______, a unit named after Volta.

Resistance is anything that resists an electric current. It is measured in _____.

Words: volts, amps, ohms, voltage, ammeter, voltmeter


More basic ideas

More basic ideas…

If a battery is added the current will ________ because there is a greater _____ on the electrons

If a bulb is added the current will _______ because there is greater ________ in the circuit


Current in a series circuit

Current in a series circuit

If the current here is 2 amps…

The current here will be…

The current here will be…

And the current here will be…

In other words, the current in a series circuit is THE SAME at any point


Current in a parallel circuit

Current in a parallel circuit

Here comes the current…

Half of the current will go down here (assuming the bulbs are the same)…

And the rest will go down here…

A PARALLEL circuit is one where the current has a “choice of routes”


Current in a parallel circuit1

Current in a parallel circuit

And the current here will be…

The current here will be…

The current here will be…

The current here will be…

If the current here is 6 amps


Some example questions

Some example questions…

3A

6A


Voltage in a series circuit

Voltage in a series circuit

V

If the voltage across the battery is 6V…

…and these bulbs are all identical…

V

V

…what will the voltage across each bulb be?

2V


Voltage in a series circuit1

Voltage in a series circuit

V

If the voltage across the battery is 6V…

…what will the voltage across two bulbs be?

V

4V


Voltage in a parallel circuit

Voltage in a parallel circuit

If the voltage across the batteries is 4V…

What is the voltage here?

V

V

And here?

4V

4V


Summary

Summary

In a SERIES circuit:

Current is THE SAME at any point

Voltage SPLITS UP over each component

In a PARALLEL circuit:

Current SPLITS UP down each “strand”

Voltage is THE SAME across each”strand”


An example question

An example question:

6V

A3

3A

A1

V1

A2

V2

V3


Another example question

Another example question:

10V

A3

3A

A1

V1

A2

V2

V3


Resistance

Resistance

Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me.

Georg Simon Ohm 1789-1854

V

Resistance = Voltage (in V)

(in )Current (in A)

I

R

The resistance of a component can be calculated using Ohm’s Law:


An example question1

An example question:

Ammeter reads 2A

A

V

Voltmeter reads 10V

  • What is the resistance across this bulb?

  • Assuming all the bulbs are the same what is the total resistance in this circuit?


More examples

More examples…

3A

3A

2A

4V

2V

1A

6V

12V

What is the resistance of these bulbs?


Resistance1

Resistance

Resistance (Ohms, ) = Potential Difference (volts, V)

Current (amps, A)

Resistance is anything that opposes an electric current.

  • What is the resistance of the following:

  • A bulb with a voltage of 3V and a current of 1A.

  • A resistor with a voltage of 12V and a current of 3A

  • A diode with a voltage of 240V and a current of 40A

  • A thermistor with a current of 0.5A and a voltage of 10V


Resistors bulbs and diodes

Resistors, bulbs and diodes


Current voltage graphs

Current-Voltage Graphs


Current voltage graphs1

Current-voltage graphs

I

I

I

V

V

V

3. Diode

1. Resistor

A diode only lets current go in one direction – it has very high resistance in the other direction

Current increases in proportion to voltage

2. Bulb

As voltage increases the bulb gets hotter and resistance increases


Ldrs and thermistors

LDRs and Thermistors


Two simple components

Two simple components:

Resistance

Resistance

Amount of light

Temperature

1) Light dependant resistor – resistance DECREASES when light intensity INCREASES

2) Thermistor – resistance DECREASES when temperature INCREASES


Wiring a plug

Wiring a plug

1.

4.

5.

2.

6.

3.

Earth wire

Live wire

Fuse

Neutral wire

Cable grip

Insulation

The neutral wire of a plug stays at a potential close to zero relative to the Earth

The live wire of a plug alternates between positive and negative potential relative to the Earth


Dc and ac

DC and AC

V

DC stands for “Direct Current” – the current only flows in one direction:

Time

1/50th s

AC stands for “Alternating Current” – the current changes direction 50 times every second (frequency = 50Hz)

230V

T

V


Using an oscilloscope

Using an oscilloscope

This number tells you how many seconds each square on the horizontal axis represents

This number tells you how many volts each square on the vertical axis represents

Q. What is the voltage and frequency of this supply?


Fuses

Fuses

Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____.

Words – large, harm, safety, melt, live, circuit, fuse


Power and fuses

Power and fuses

P

V

I

Power is “the rate of doing work”. The amount of power being used in an electrical circuit is given by:

Power = voltage x current

in W in V in A

Using this equation we can work out the fuse rating for any appliance. For example, a 3kW (3000W) fire plugged into a 240V supply would need a current of _______ A, so a _______ amp fuse would be used (fuse values are usually 3, 5 or 13A).


Power and fuses1

Power and fuses

Copy and complete the following table:


Energy and power

Energy and Power

E

P

T

The POWER RATING of an appliance is simply how much energy it uses every second.

In other words, 1 Watt = 1 Joule per second

E = Energy (in joules)

P = Power (in watts)

T = Time (in seconds)


Some example questions1

Some example questions

  • What is the power rating of a light bulb that transfers 120 joules of energy in 2 seconds?

  • What is the power of an electric fire that transfers 10,000J of energy in 5 seconds?

  • Farhun runs up the stairs in 5 seconds. If he transfers 1,000,000J of energy in this time what is his power rating?

  • How much energy does a 150W light bulb transfer in a) one second, b) one minute?

  • Shaun’s brain needs energy supplied to it at a rate of 40W. How much energy does it need during a physics lesson?

  • Damien’s brain, being more intelligent, only needs energy at a rate of about 20W. How much energy would his brain use in a normal day?


Earth wires

Earth wires

Earth wires are always used if an appliance has a _____ case. If there is a _____ in the appliance, causing the live wire to ______ the case, the current “_______” down the earth wire and the ______ blows.

Words – fuse, fault, metal, surges, touch


Charge q

Charge (Q)

Q

I

T

As we said, electricity is when electrons move around a circuit and carry energy with them. Each electron has a negative CHARGE. Charge is measured in Coulombs (C). We can work out how much charge flows in a circuit using the equation:

Charge = current x time

(in C) (in A) (in s)


Example questions4

Example questions

  • A circuit is switched on for 30s with a current of 3A. How much charge flowed?

  • During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for?

  • A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed?


Energy and charge

Energy and charge

E

V

Q

The amount of energy that flows in a circuit will depend on the amount of charge carried by the electrons and the voltage pushing the charge around:

Energy transferred = charge x voltage

(in J) (in C) (in V)


Example questions5

Example questions

  • In a radio circuit a voltage of 6V is applied and a charge of 100C flows. How much energy has been transferred?

  • In this circuit the radio drew a current of 0.5A. How long was it on for?

  • A motor operates at 6V and draws a current of 3A. The motor is used for 5 minutes. Calculate: a) The motor’s resistance, b) the charge flowing through it, c) the energy supplied to it

  • A lamp is attached to a 12V circuit and a charge of 1200C flows through it. If the lamp is on for 10 minutes calculate a) the current, b) the resistance, c) the energy supplied to the bulb.


Random questions2

Random questions

  • A battery has a voltage of 12V and it puts a current of 3A through a bulb. What is the bulb’s resistance?

  • Another bulb transfers 120C of charge in 2 minutes. What was the current through it?

  • A powerpack transfers 2,000J to a motor. If the motor ran on a voltage of 50V how much charge was transferred?

  • A hairdryer runs on a 50Hz power supply. If it has a power rating of 200W what fuse should it have?

  • An electric fire transfers 3MJ of energy. If it has a power rating of 2KW calculate how long it was on for, the current it ran on (assuming it was connected to the mains supply) and the amount of charge it transferred.


Structure of the atom

Structure of the atom

A hundred years ago people thought that the atom looked like a “plum pudding” – a sphere of positive charge with negatively charged electrons spread through it…

Ernest Rutherford, British scientist:

I did an experiment (with my colleagues Geiger and Marsden) that proved this idea was wrong. I called it the “Scattering Experiment”


The rutherford scattering experiment

The Rutherford Scattering Experiment

Alpha particles (positive charge, part of helium atom)

Thin gold foil

Most particles passed through, 1/8000 were deflected by more than 900

Conclusion – atom is made up of a small, positively charged nucleus surrounded by electrons orbiting in a “cloud”.


The structure of the atom

The structure of the atom

ELECTRON – negative, mass nearly nothing

PROTON – positive, same mass as neutron (“1”)

NEUTRON – neutral, same mass as proton (“1”)


The structure of the atom1

The structure of the atom

MASS NUMBER = number of protons + number of neutrons

4

He

SYMBOL

2

PROTON NUMBER = number of protons (obviously)


Isotopes

Isotopes

Notice that the mass number is different. How many neutrons does each isotope have?

16

O

17

18

O

O

8

8

8

Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.

An isotope is an atom with a different number of neutrons:

A “radioisotope” is simply an isotope that is radioactive – e.g. carbon 14, which is used in carbon dating.


Background radiation

Background Radiation

13% are man-made

Radon gas

Food

Cosmic rays

Gamma rays

Medical

Nuclear power


Types of radiation

Types of radiation

New nucleus

1) Alpha () – an atom decays into a new atom and emits an alpha particle (2 protons and 2 ______ – the nucleus of a ______ atom)

Unstable nucleus

New nucleus

Alpha particle

2) Beta () – an atom decays into a new atom by changing a neutron into a _______ and electron. The fast moving, high energy electron is called a _____ particle.

Beta particle

Unstable nucleus

3) Gamma – after  or  decay surplus ______ is sometimes emitted. This is called gamma radiation and has a very high ______ with short wavelength. The atom is not changed.

Words – frequency, proton, energy, neutrons, helium, beta

Unstable nucleus

New nucleus

Gamma radiation


Nuclear fission

Nuclear fission

More neutrons

Neutron

Unstable nucleus

Uranium or plutonium nucleus

New nuclei (e.g. barium and krypton)


Chain reactions

Chain reactions

Each fission reaction releases neutrons that are used in further reactions.


Nuclear fusion in stars

Nuclear Fusion in stars

Proton

Neutron


Aqa additional science

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