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Educational resources: Sample model answers

Describe the steps for producing a drawing that shows form

by Wendy Fewtrell

Background

Success in drawing depends on following a simple, clear order in the approach to the subject. If this discipline is adopted, it is possible for anyone to achieve a reasonable degree of success.

Full answer

The first step is to choose an object to draw. It is best to make this a very simple object to start with. When aiming for success in capturing form, it is important to choose an object that is not too complicated. For example, an apple without any markings or colour change would be a good choice.

lighting the object

In lighting an object, the following guidelines are important:

• the object should be placed on white paper – this will help show how the light is falling on the object itself and will also clearly show the cast shadow
• the object should be lit from one side, either by natural light (for example, by putting it on a windowsill) or artificial light (for example, with a lamp)
• sit in a position where the object can be viewed clearly
• have the drawing equipment to hand
• look carefully at the object.

the next stages

sketching

• lightly sketch the shape of the apple, trying to keep the drawing reasonably large
• use an HB pencil – this will give a faint, pale outline; if the pencil has accidentally been pressed too hard, the rubber can be used to make the outline paler; the outline should not show on a drawing that is concerned with form – outlines flatten the effect trying to be achieved.

shading – the cast shadow

• sketch the shape of the shadow – notice the shadow has depth
• the cast shadow is always darkest, tucked well in, near to the object – this darkest part should be drawn first, using a 2B pencil
• change to a B pencil and gradually continue to shade the shadow outwards, finishing with the HB on the outside edge – this edge should be very pale indeed, dissolving away to nothing on the white paper
• no evidence of the original sketched outline of the shadow should be seen.

At this point in the drawing, a fair amount of form should have been achieved already.

shading on the object

• begin on the darkest side away from the light source, using a 2B to begin to shade
• in order for the drawing to be effective, it is important to differentiate between the darkest part of the object and the darkest part of the cast shadow – if they are the same, the object will merge into the shadow; the differentiation can be achieved either by shading the object so that it is considerably darker than the dark part of the shadow, or by making it paler
• continue to shade, changing the grade of pencils as the lighter side of the apple is drawn – it is important to keep looking at how the light and shade change as they fall on the apple
• no outline should be visible around the edge of the object when the drawing is finished.

Look critically at the completed work – it should have achieved a good range of shades and contrast (some parts of the shading may need to be reworked to achieve this fully).

In short

In creating a drawing that demonstrates form, it is important to:

• choose a simple object to start with
• remember the aims – the goal is to make the drawing appear three-dimensional
• use a wide range of shades to create contrast
• use different grades of pencil to achieve different effects
• make sure that no outlines are visible when the drawing is finished
• always include any cast shadow.

How are the teeth of mammals adapted to a carnivorous, herbivorous, and omnivorous diet?

by Keith Lawn

Background

The teeth of mammals are used to begin the process of digestion. Food is bitten into small pieces and chewed to increase its surface area (and to allow swallowing). It is then acted on by enzymes. The shapes of a mammal's teeth are closely related to its diet.

Full answer

carnivores

These animals, for example lions and dogs, catch live prey and kill it using their teeth. They bite the meat into chunks, so that it can be swallowed. They do not need to grind their food, as most digestion is carried out in the stomach by protein-digesting enzymes.

Carnivores' dental features include:

• incisors – small, chisel-shaped teeth used to tear flesh away from the bone
• canines – large, slightly curved, and pointed teeth used for piercing, killing, and holding struggling prey and for tearing off larger pieces of flesh
• premolars and molars – featuring prominent ridges, these teeth act as powerful shears, cutting flesh into manageable pieces, and cracking bones; the largest are called carnassial teeth.

herbivores

These animals, for example rabbits and sheep, eat vegetation. They use their teeth for cutting through tough grass and stems. They then grind open the cellulose cell walls to expose the cell contents. This process wears away herbivores' teeth, so their teeth grow continually.

Herbivores have the following dental features:

• incisors – sharp teeth that snip off vegetation
• in sheep and cows a horny pad against which lower incisors bite has replaced upper incisors
• no canine teeth
• a diastema – a gap between incisors and premolars that allows the tongue to manipulate freshly cut vegetation
• premolars and molars – interlocking teeth with sharp enamel ridges to grind through the tough cellulose walls of vegetable matter.

omnivores

These animals, for example pigs and humans, eat both plant and animal food. Their teeth show no special adaptations.

Omnivores' dental features include:

• incisors – sharp teeth that allow flesh or vegetables to be cut
• canines – pointed but small teeth used for cutting
• premolars and molars – flat teeth with rounded cusps used for chewing rather than for grinding.

In short

Mammals' teeth are adapted for different diets:

• carnivores catch and kill live prey and tear it into edible pieces using their teeth
• herbivores cut and grind vegetation with their teeth
• omnivores use their teeth to cut and chew both plant and animal food.

Plastics possess many special properties. Describe how plastics are made, their characteristics, and the different types of plastics available

by Joyce Shorrock

Full answer

The raw materials for plastics are organic molecules that come from oil. Without crude oil plastics would be very difficult to produce. The small units that are put together to form plastics are called monomers. Monomers join into long chains called polymers (plastics).

how plastics are made

Many plastics are made by addition reactions. These require an alkene monomer (containing a carbon-to-carbon double bond). The double bond opens up and the monomer units join. Styrene is an alkene monomer – it polymerizes to form polystyrene. Ethene is the monomer that polymerizes to form polyethene (or polythene).

general characteristics of plastics

Plastics have the following characteristics:

• non-conducters of electricity – used as insulators, around electrical cables and in plugs
• not affected by acids and alkalis – used in the laboratory for containers
• non-biodegradable – used where a non-rotting material is required
• combustible, giving off toxic gases when burning.

types of plastics

Thermosoftening plastics can be heated and formed into a particular shape. They can be reheated and reshaped a number of times: the plastic can be softened repeatedly.

Thermosetting plastics are different. Once the polymer has been formed, heated, made into a particular shape, and cooled, it cannot be reheated and reshaped. The plastic is set into a particular structure.

plastics and bonds

The polymer units that make up a plastic can be held together with bonds. This gives the plastic some strength. The presence, number, and type of these cross-linking bonds determine whether the plastic is thermosetting or thermosoftening.

Initially a thermosetting plastic has no cross-linking bonds, so the plastic can be heated and softened. Once the plastic has been cooled and formed into a particular shape, covalent cross-link bonds are made, which hold the polymer chains together. These bonds are difficult to break so continue to hold the plastic in its set shape. Thus the plastic cannot be melted and softened again.

The long-chain polymers in thermosoftening plastics have no such cross-links between them. The polymer chains are only relatively loosely attracted to each other. When heated the polymer chains can be separated from each other and the plastic melts. Once cooled, the weak forces are re-formed so the solid plastic has some strength.

why polythene stretches

Polythene is made up of polymer strands that are only weakly attracted. When the polythene is pulled the chains are separated from each other. As they slide past each other, the plastic stretches.

In short

Plastics are made from substances extracted from crude oil:

• the small units that make up a plastic are called monomers; they join together to form polymers
• polymers can be made by addition reactions
• plastics have properties that are characteristic of their covalent bonds
• plastics are resistant to acids and alkalis
• plastics burn to form toxic compounds
• plastics are of two types: thermosoftening and thermosetting
• if there are only weak bonds between the polymer strands then the plastic is thermosoftening
• if there are cross-links between the polymer strands then the plastic is thermosetting
• thermosetting plastics cannot be remodelled
• thermosoftening plastics can be remodelled
• polythene can stretch as there are no cross-link bonds present.

How does the law affect young people?

by Mary Myatt

Background

Countries have laws to protect their citizens and keep order. Everyone is subject to the law and must pay the penalty if they break it. However, they are also entitled to its protection.

Full answer

Laws exist to ensure children are not exploited at work or home, and that children and young people have opportunities in life. In the UK, children must be in full-time education until 16. A 'child' in law is anyone under 16; a 'young person' is someone over 16 but under 18.

what does the law say about children working?

If children want to earn money they can, but there are laws to stop exploitation. A child cannot be employed:

• under the age of 12
• during school hours
• before 7 a.m. or after 7 p.m.
• for more than two hours on a school day
• for more than two hours on a Sunday
• in an industrial setting or where there could be injury from lifting or moving heavy items.

who checks on children's employment?
Local education authorities can restrict or prohibit some types of employment, even if not illegal, if children are believed to be in danger.

are there laws about what children can buy?

Laws exist regarding what children are allowed to buy and do at different ages. A child can buy a pet at 12, tobacco and fireworks at 16, have a bank account from birth, and withdraw money from 7. A child can go into a bar with an adult, but not buy or drink alcohol, from 14. They can buy alcohol at the age of 18.

what other laws affect young people?

Everyone in the UK (apart from the mentally ill or impaired in institutions, peers, and those in prison) has the right to vote from 18. A young person can ride a moped (with an engine up to 50cc) from 16, drive a car with a provisional licence from 17, and stand for election as a local councillor or MP at 21.

what happens when young people break the law?

A child can be convicted of a criminal offence from the age of 10. From the age of 14 they can be fingerprinted if they agree or if a magistrate orders it. A young person can be jailed for a criminal offence from 17. It is important to understand the law, because ignorance of it cannot be used as an excuse.

In short

• laws ensure young people have fair opportunities
• in law, a child is someone under the age of 16; a young person is someone over 16 but under 18
• there are laws to protect children from exploitation and to set basic standards for their employment
• there are laws about what young people can buy and what they are allowed to do at different ages
• a child can be convicted of breaking the law from the age of 10
• a young person can be sent to prison from the age of 17.

Ergonomics has become a standard design consideration over the last decade or so, as consumers have become more discerning and manufacturing technology more flexible. Using examples from daily life, consider how ergonomics has played a part in their design

by Ruth Stafford

Background

Ergonomics is about people, objects, and environments, and how they interact. Questions such as:

• is it safe?
• is it comfortable?
• is it easy to use?
• are all concerned with ergonomics.

Full answer

Anthropometrical data is often used to help designers make a product or environment more ergonomic. Anthropometric data is information about people's body sizes, for example, height or distance from floor to knee. Designers also take into account physiological factors, such as people's strength and range of movement, and psychological aspects, such as feelings and reactions associated with different smells, colours, and sounds.

ergonomics in the workplace

Ergonomics is becoming more and more important in workplace design as people are suffering from illness and injury as a result of poor design.

One example is repetitive strain injury (RSI), which occurs when the same movement is repeated over a long period of time, causing strain on a particular body part. Using a computer keyboard and mouse has been one common cause of RSI. Today, computer keyboards have front panels to rest the wrist on and the design of the mouse has changed over the years to make it more comfortable for the hand.

ergonomics in the home

Everyday objects, such as the plug, have been affected by ergonomics. Plugs now have moulded handles on the back to make it easier for them to be pulled out of the socket. This means that a wider range of people can comfortably use them.

The designs of objects such as the telephone, hairdryer, and kettle have all taken ergonomics into consideration. For example, some telephones have large buttons for the poorly sighted; hairdryers have moulded grip handles to make them easier to hold with damp hands; kettles are cordless to make pouring easier and can even be made to change colour when boiling, which acts as a safety indicator.

ergonomics in public facilities

Shopping halls are carefully designed and laid out to suit a wide range of people. They incorporate facilities for disabled people and people with small children. Psychological aspects of colour, smell, and noise are taken into account, with fountains and seating areas for taking breaks.

Public toilets are becoming more accessible to all. The large plastic door latches are now as easy for 4- and 5-year-olds to open (whose fingers are not yet as dextrous as adults'), as they are for the older person whose fingers are restricted by arthritis.

the benefits of ergonomic design

The old phrase 'one size fits all' now has a more applicable meaning. Instead of having to make do with one size, people are now better able to use the one size because more ergonomic thought is going into the design of products and environments.

In short

• ergonomics is to do with how people interact with their environments and the products they use
• anthropometrics is the data collected on people's body sizes and proportions
• physiological aspects to be considered in design include people's range of movement and strength
• psychological aspects include people's reactions and feelings associated with smell, colour, sound, taste, and texture.

How are apostrophes used?

by Sue Williams

Background

Many people find apostrophes difficult to use and tend to guess when they are needed. This answer will explain how to use apostrophes correctly by showing when they are and are not needed. There are definite rules for using apostrophes – unlike much of English, there is a right and wrong way of using them.

Full answer

when are apostrophes not needed?

Apostrophes are not needed when simply using a plural. The plural form of a word is used when there is more than one of something. For most words this means adding an 's' to the end of the word. The following words are all plural: handbags, fingers, televisions, computers, chocolates, and cats. There are also many English words that have more complicated ways of being made plural. But an apostrophe is never used to make words plural.

when are apostrophes needed?

Apostrophes are needed when you are showing that a person or thing belongs to someone or something. For example, to show that the cat belongs to Sarah, you would write 'Sarah's cat'. Similarly, to show that the room belongs to Kamaljit, you would write 'Kamaljit's room'. Here are more examples:

• the desk belongs to Owen – Owen's desk
• these cakes belong to George – George's cakes
• Jane owns this scooter – Jane's scooter
• this dress belongs to Angela – Angela's dress.

If the word already ends in 's', apostrophe 's' is still added. For example, the dogs belonging to James – James's dogs.

To show that several people own something, the rule is slightly different. For example, if the teachers own the books, this becomes 'the teachers' books'. In this case, the apostrophe is placed after the 's'.

If the apostrophe is put before the 's' the phrase becomes: 'the teacher's books'. This changes the meaning by indicating only one teacher. 'The teacher's books' means the books of one teacher only, not a whole group of teachers. This is why the rule exists – to show who owns what. Some more examples:

• the books that Robert has – Robert's books
• the socks being worn by the twins – the twins' socks
• the car being driven by Mr Long – Mr Long's car
• the houses owned by the sisters – the sisters' houses
• the lives of the princesses – the princesses' lives.

using apostrophes to shorten words

An apostrophe can also be used to shorten a word. For example, 'isn't' is short for 'is not'. 'Can't' is short for 'can not'. 'It's' is short for 'it is', 'John's catching the train' is short for 'John is catching the train'. The apostrophe replaces the missing letter or letters. The way to know if a word is being shortened is to sound out the full version.

In short

Apostrophes are used to:

• show belonging
• shorten words.

Apostrophes are not used to:

• make a plural.

What are the main coastal features resulting from erosion and deposition?

by Steve Dann

Background

Coastal landforms are a result of marine processes, weathering, and human activities. The type of landform produced varies according to geology and weather conditions. Some landforms, such as beaches, can change quickly, for example after a single storm event, while others, like chalk headlands, erode at a very slow rate. Average rates of erosion can be misleading as some coastlines wear away constantly, while others collapse suddenly.

Full answer

features resulting from erosion

cliffs
Cliffs result from hydraulic action, abrasion, and corrosion undercutting the rock and forming a notch. As this notch is enlarged into a cave, the supporting strength of the cliff face is reduced and it eventually collapses. As the cliff retreats inland, it leaves a wave-cut platform at the low tide level.

The angle of the cliff depends on:

• the type of rock
• whether or not the rock has been folded by tectonic movements
• the rate of weathering.

If marine processes are powerful, the cliff is likely to be very steep; if weathering erodes the top of the cliff rapidly then it will take on a gentler profile.

bays and headlands
These are the result of erosion taking place at different rates along a coastline. Less resistant rock types, such as clays, will retreat more quickly than more resistant ones, such as limestone, resulting in an uneven coast.

• discordant coasts have bands of different types of rock lying at right angles to the shoreline, creating wide bays and prominent headlands
• concordant coastlines have bands of rock running parallel to the shoreline, usually resulting in narrow-mouthed, protected bays, such as Lulworth Cove in Dorset.

arches, stacks, and stumps
Wave refraction concentrates erosive forces on to a headland, where the sea will attack the weakest points such as fault lines or joints. These faults can be widened to form caves. As a cave is further eroded, a natural arch may develop through the headland. Continued attack will cause the roof of the arch to collapse, leaving a column of rock isolated from the mainland. This is known as a stack and will be reduced to a stump over time. A series of stacks and stumps, for example the Needles off the Isle of Wight, can become a major tourist attraction.

features resulting from deposition

beach
The main coastal feature resulting from deposition is the beach. Beaches come in many shapes and sizes depending on the nature of the material they are made of and the waves that form them. Larger material, such as pebbles, tends to form steeper beaches than sand.

Beach profiles (cross sections) are often made up of a series of ridges, or berms, corresponding to the different tide levels. The highest ridge, called the storm ridge, will contain the largest pebbles as only the biggest waves have the power to throw them that far.

spits
Spits are sand or pebble beaches joined to the land at one end. They result from longshore drift transporting material away from the shore due to a change in the shape of the coastline across a river mouth or bay. The seaward end of the spit is often recurved or hooked due to a change in wave direction. Salt marshes or mud flats are sometimes found in the protected calmer water behind the spit. Spits give a good indication of the direction of longshore drift.

If a spit grows right across a bay it is known as a bay bar and may have a lagoon behind it. Spits that link the mainland to an island are known as tombolos. Chesil Beach to the Isle of Portland in Dorset is the best known example of a tombolo.

In short

The sea can erode material from one area of the coastline and deposit it at another. Coastal features resulting from erosion are:

• cliffs
• bays and headlands
• arches, stacks, and stumps.

Deposition leads to the formation of:

• beaches
• spits.

How did the Bolsheviks manage to win the Russian civil war of 1918–21?

by Stephen Drew

Background

The Bolsheviks seized power in Russia in October 1917 when they were still a relatively small group. Opponents of the Revolution made a series of military attacks that lasted from 1918 to 1920. At the end of 1919 the Bolsheviks were in control of less than one quarter of the country. However, by the end of 1920 the Bolshevik Red Army had defeated their enemies, the Whites, and the Bolsheviks went on to rule Russia for the next 70 years.

Full answer

the Bolsheviks had many advantages

• the Bolsheviks were a united, organized, and efficient revolutionary force
  The party organization was set up for revolutionary struggle. The Bolsheviks were loyal to the party leadership and prepared to make huge sacrifices in the name of the revolution. They were also well-organized, efficient, and able to control dissent very effectively.
• they had a committed revolutionary army
  The Bolsheviks established a revolutionary army, the Red Army. It involved committed revolutionaries fighting for what they perceived to be Russia's freedom.
• the Red Army had effective leadership and was strongly united
  The Red Army was led by Leon Trotsky, a highly effective leader, who managed to motivate his men even when they were suffering major defeats in 1918. The Red Army was also strongly united in its cause.
• the Bolsheviks had great resources of materials and manpower
  Russian industry was centred on Moscow and Petrograd (St Petersburg). These cities were under the control of the Bolsheviks. Moscow was also the centre of Russia's railway network – this enabled the Bolsheviks to transport soldiers and supplies easily.
• the Bolsheviks could claim to be truly Russian
  The Red Army claimed to be fighting for the freedom of Russia from foreign domination. The Bolsheviks had no outside support, and relied totally on the efforts of Russians. In this way they could present their struggle as one for the soul of Russia and themselves as the true defenders of Russia's rights.

the Whites had major disadvantages

• the Whites were disunited
  It was easier for the Bolsheviks to target the White armies one by one and destroy them because the White armies were not united.
• the Whites were not coordinated
  There was no single commander of the anti-Bolshevik White forces and attacks were not coordinated. White army leaders, such as Admiral Alexander Kolchak and General Anton Denikin, often had different aims or ideas about the future of Russia, so actively refused to work together.
• the Whites relied on foreign aid
  World War I was still going on in 1918. The UK, France, and the USA wanted Russia to re-enter the war against the Germans, and saw the Whites as a way to get Russia to do this. Therefore they gave them support. Money, supplies, and even some soldiers were sent to Russia.
  However when the war ended in November 1918, this support soon ended too. The Whites were left without the vital supplies of weapons and ammunition that had sustained their initial campaigns.
• the Whites' leaders were unpopular
  The leaders of the Whites were unpopular with many Russians because they were nobles and officers of the old regime. The generals of the Whites tried to reimpose the old tsarist system on Russia in areas they controlled.
• the Whites were not seen as patriotic
  The Whites were allied with foreign powers – so patriotic Russians turned to the Bolsheviks because they were seen as truly Russian.

the Bolsheviks were ruthless in their pursuit of victory

The Bolsheviks took the strongest possible measures to ensure victory. These policies were called war communism:

• workers in factories were forced to support the war effort
• workers' rights were restricted even more than they had been under the tsarist system
• the Bolsheviks forced the peasants to give them their grain supplies – without grain, the workers would leave the cities and the Red Army would not be able to fight
• peasants who refused to help the Bolsheviks were heavily punished, with whole villages killed as examples to other peasants.

In short

The Bolsheviks won the Russian civil war because:

• they were a strong and united revolutionary group
• the Red Army was effectively led and united in the pursuit of its cause
• the Bolsheviks controlled the majority of Russia's industry and population
• the Bolsheviks controlled the railway network
• the Bolsheviks presented their struggle as a patriotic cause
• the Whites were disunited
• the Whites relied too heavily on foreign aid
• White leaders pursued unpopular policies in the areas they controlled
• the Bolsheviks were ruthless in their pursuit of victory.

Explain what is meant by system security

by Gina Patterson

Full answer

system security

System security is the protection of information, systems, and services against disasters, mistakes, and manipulation, so that the likelihood and impact of security incidents is minimized.

confidentiality

Unauthorized users should not have access to sensitive data.

integrity

Controls are required when accessing the computer system to ensure that the data remains reliable and does not become corrupted.

availability

Controls are required to ensure that the data is available in the computer system as and when required.

threat

Threats are a danger that could have an effect on the computer system's data and performance in the future.

improving security

Steps that can be taken to assist in the security of the computer system include:

• knowing what data and processes need to be protected
• recognizing potential threats, and then working out possible impacts
• analysing the risks, and then deciding what risks are acceptable
• creating a strategy to reduce the risk to an acceptable level, then implementing, testing, and tuning the strategy
• keeping it simple; if security is very complicated, it is unlikely to be effective and likely to be expensive
• keeping it consistent; it is better to have a minimum level of security across all systems rather than have some systems highly protected and other dependent systems wide open
• keeping to industry standards if possible; it will make choosing and evaluating systems easier and will allow easier definition of inter-company standards

In short

System security is the protection of data, systems, and services against disasters, mistakes, and manipulation so that the likelihood and impact of security incidents is minimized.

Areas to consider include:

• confidentiality
• integrity
• availability
• threat.

Steps that can be taken to assist in the security of the computer system include:

• knowing the data and processes
• recognizing threats
• analysing the risks
• creating a strategy
• keeping it simple
• keeping it consistent
• keeping to industry standards.

A school carried out a survey to find out what pupils would most like as the prize for a fund-raising raffle. The choices were a mobile phone, hi-fi equipment, or a cash prize. When the votes were counted they were in a ratio of 5:4:3. All pupils voted in the survey and 350 pupils voted for the mobile phone. (a) How many pupils are there at this school? (b) How many pupils voted for the cash prize?

by Wilf Hodgson

Background

A ratio is a way of comparing two or more amounts. The ratio is expressed as a:b, where a and b are integers (whole numbers). If a and b can be divided by the same whole number then the ratio can be expressed in a simpler form and if this is continued until no further division is possible, then the ratio is expressed in its lowest terms.

For example, a class has 18 girls and 12 boys in it. The ratio of girls to boys is 18:12.

This can be simplified by dividing by 2 to get a ratio 9:6. This can be further simplified by dividing by 3 to get the ratio in its lowest terms of 3:2. This means that when comparing the number of girls to the number of boys in this class, for every three girls in the class there are two boys.

Ratio can also be thought of as a way of sharing an amount among two or more people. For example, Andy, Bernice, and Carol share 36 chocolate bars in the ratio 2:3:4. How many chocolate bars would each one receive? (If you can, picture them sitting with a pile of chocolate bars in front of them and sharing them as, 'two for Andy, three for Bernice, four for Carol, two for Andy, three for Bernice, four for Carol', and so on until all of the bars have gone from the pile.)

We can see that every time there is a 'share' we need 2 + 3 + 4 = 9 chocolate bars. Since there are 36 chocolate bars, we can have 36 ÷ 9 = 4 shares. Every time there is a share, Andy gets 2 bars, Bernice gets 3 bars, and Carol gets 4 bars. So Andy will get 4 × 2 = 8 bars, Bernice gets 4 × 3 = 12 bars, and Carol gets 4 × 4 = 16 bars.

We can work from a given share and a given ratio to find the total amount and the value of other shares by 'working backwards' using this method. For example, Anna, Bill, and Carl are given an amount of money to be shared in the ratio of their ages. Anna is 12, Bill is 14, and Carl is 20 and Carl receives £138. How much would the others expect to receive? The ratio of their ages 12:14:20 can be simplified to 6:7:10 by dividing each age by 2.

From this we can see that every time there would be a share, Anna would get £6, Bill would get £7, and Carl would get £10. This tells us that for every share we need a total of 6 + 7 + 10 = £23. At the end of the sharing Carl has got £138 and every share gave him £10 so there must have been 138 ÷ 10 = 13.8 shares. This is not very practical in terms of how it could have happened with them sitting around a pile of money but mathematically it is nothing to worry about. Every share needed a total of £23, so the total amount of money can be calculated by 13.8 × 23 = £317.40. Each share gives Anna £6 so she gets 13.8 × 6 = £82.80, and Bill gets 13.8 × 7 = £96.60.

Full answer

(a) finding how many pupils there are at this school

There were 5 + 4 + 3 = 12 votes needed in every share of the votes. We are told that for every share the mobile phone got 5 votes and a total of 350 votes tells us that there were 350 ÷ 5 = 70 shares. We can now work out the total number of pupils as it is the same as the total number of votes. 70 shares each with 12 votes gives 70 × 12 = 840.

answer: 840 pupils

(b) finding how many pupils voted for the cash prize

For every share the cash prize received 3 votes. Therefore after 70 shares the cash prize would have got 70 × 3 = 210 votes.

answer: 210 pupils

In short

• a ratio is a way of comparing two or more amounts or shares, expressed as a:b
• if a and b can be divided by the same whole number then the ratio can be expressed in a simpler form
• when no further division is possible, then the ratio is expressed in its lowest terms.

What is ragtime music?

by Marian Tomkinson

Background

Ragtime is a style of music that originated in the USA during the early 1900s. It was rooted in the music brought to the country by African slaves. Because of ragtime's African roots, the music was predominantly composed and favoured by black Americans; some of the music made fun of white Americans.

Full answer

characteristics of ragtime music

Ragtime music was mostly written to be played on the piano, but occasionally it used other instruments, including the banjo.

Most ragtime piano music had a steady left-hand part, which essentially kept the beat throughout the piece, as well as providing a chordal accompaniment.

The right-hand part would usually be more complicated. It tended to be spiky and jerky in sound, often twice the speed of the left-hand part, and syncopated, which means 'off beat', where one part is accented against the steady beat of the other part. The 'ragged time' of the right-hand part led to the term ragtime.

dancing

Many people are tempted to play ragtime music at great speed, but much of it is intended to be fairly steady in tempo, particularly as it was often composed to be used as dancing music.

composers

There are several famous composers of ragtime, but the most famous of all is probably Scott Joplin (1868–1917), who composed well-known pieces such as The Entertainer and Maple Leaf Rag.

Claude Debussy (1862–1918), noticed the popular trend of ragtime music and composed the Golliwog's Cakewalk using some of the key characteristics of the music.

ragtime today

Ragtime was extremely popular during the 1900s and, although few people still dance to it, many pianists enjoy learning the challenging parts and memorable melodies. Ragtime music is frequently used in films, such as The Sting (1973), and in television programmes.

In short

• ragtime originated in the USA in the early 1900s from music brought to the continent by African slaves
• most ragtime was written for the piano, usually with a steady left-hand part and a complicated, syncopated right-hand part
• ragtime music often accompanied dancing
• one of the most famous ragtime composers was Scott Joplin.

What is an electromagnet? What are the uses of electromagnets?

by Richard Gill

Background

A compass is a magnet. When allowed to swing freely, one end will point to the north, the other end will point to the south. This is because the Earth has a magnetic field around it. A magnet usually has two poles, a north pole and a south pole. When suspended freely the north pole will point northward and the south pole will point southwards.

Materials that can be made into magnets include iron and steel. Nonmagnetic materials include plastic, copper, wood, and aluminium. A magnet can be made from an iron bar by continually stroking it in the same direction with another magnet, so that the domains are all facing the same way.

Full answer

making an electromagnet

When an electric current flows through a wire, a weak magnetic field is produced around it. To increase the strength of the magnetic field, the wire can be made into a solenoid (a long coil). When a current passes through a solenoid it creates a magnetic field that has the same shape as the magnetic field around a bar magnet. If the direction of the current flowing through the solenoid is reversed, the direction of the magnetic field is also reversed. If a soft iron bar is placed inside the coils, the magnetic effect is increased. This combination of solenoid and soft iron core is called an electromagnet.

The strength of an electromagnet can be increased by:

• increasing the number of coils of wire
• increasing the current flowing through the wire.

uses of electromagnets

Electromagnets are useful because they are not permanently magnetized and can be switched on and off. They have many uses, including:

• magnetic cranes
  Electromagnets are used in scrapyards to move large amounts of heavy iron and steel about. An electromagnet fitted onto the crane makes this easier.
• relays
  These are used when a smaller current is used to switch on a larger current. When the smaller current is switched on, it activates an electromagnet, which attracts an iron bar, which presses against contacts in the other circuit, switching it on.
• telephone earpieces
  Signals in the form of varying electric currents enter an earpiece. They travel through a coil creating a magnetic field which varies in strength. Next to the coil is an iron disc. The changing magnetic field causes it to vibrate and produce sounds.
• electric bells
  When the switch on the bell is pushed, it activates the electromagnet, causing a hammer to hit the bell. The movement of the hammer breaks the circuit, deactivating the electromagnet. The hammer is attached to a springy piece of metal so moves back to its original position, reconnecting the circuit and reactivating the electromagnet, causing the whole process to be repeated. This continues until the switch is no longer pushed.

In short

• an electromagnet is made by placing a soft iron core inside a coil of wire (solenoid)
• the magnetic field produced is the same as that around a bar magnet
• the strength of the electromagnet can be increased by increasing the number of turns of wire around the core and by increasing the current
• electromagnets can be used in magnetic cranes, relays, telephone earpieces, and electric bells.

What are the different methods of contraception?

by Richard Gill

Background

When an ovary releases an egg cell, it passes along the oviduct(Fallopian tube) towards the uterus. If sperm cells are present in the oviduct as the egg cell is passing down it, one of the sperm cells may join with the egg cell. This is called fertilization.

When the fertilized egg reaches the uterus it attaches itself to the uterus lining. This is called implantation. The woman is now pregnant or is said to have conceived. Contraception is a method of preventing conception.

Full answer

There are three main methods of contraception:

• preventing the sperm reaching the egg
• preventing eggs being produced
• preventing the fertilized egg implanting in the uterus.

preventing the sperm reaching the egg

The following methods prevent the sperm from reaching the egg:

withdrawal:

• the penis is removed before ejaculation
• fluids released before ejaculation may contain sperm and great control is needed for withdrawal
• this is a very unreliable method of contraception.

rhythm method:

• intercourse only takes place when there is no egg present to be fertilized
• this requires careful monitoring of the menstrual cycle
• this can be unreliable if the woman's menstrual cycle is irregular.

condom:

• this is a rubber sheath that fits over the penis and traps the sperm when ejaculation occurs
• it is often coated with a spermicide to help kill the sperm
• this is a reliable method if used correctly.

diaphragm:

• this is a rubber diaphragm that fits over the cervix, preventing sperm from entering the uterus
• this is a reliable method as long as it is fitted correctly and is used with a spermicide.

sterilization:

• in males the sperm ducts are cut and tied (vasectomy), while in females the oviducts are cut and tied (tubal ligation)
• this is a reliable method but cannot be reversed easily.

preventing eggs being produced

The following methods prevent the eggs being produced:

oral contraception (the Pill):

• this is a tablet taken daily by the female
• it prevents eggs being produced by the ovaries
• this is a reliable method if the pills are taken correctly, although there may be some side effects, such as high blood pressure.

injectable contraceptive:

• this an injection that will stop ovulation for about three months
• this is a reliable method although there are some health concerns.

preventing the fertilized egg implanting in the uterus

intra-uterine device (IUD):

• this is a plastic or metal device placed in the uterus to prevent the embryo implanting
• this is a reliable method.

morning-after pill:

• this is a tablet that can be taken up to three days (72 hours) after intercourse
• this is a reliable method, although it may cause some nausea
• it is normally only used in emergency contraception.

In short

Contraception is a method of preventing the conception of a baby. There are three main methods:

• preventing the sperm reaching the egg, for example condom, diaphragm
• preventing eggs being produced, for example oral contraceptive
• preventing the fertilized egg implanting in the womb, for example IUD, morning-after pill.

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