Yr-9 Eoy Review Ver 2

Name:

Science Class:

Score: [

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MULTIPLE CHOICE SECTION ************************************************

Which electrical appliance uses the most energy in 10 minutes of operation? A. stove

B. stereo

C. computer

D. television

If the drinking water in a particular area is naturally low in minerals, sodium fluoride can be added to the water supply in order to help children develop healthy teeth. The following passage is adapted from a magazine article on fluoridation of drinking water. The pro-fluoride lobby tends to be passionate about fluoridating water supplies because they believe the benefits — in reducing caries1 — are so self-evident. The anti-fluoride brigade can be just as forceful in putting their concerns, which often reflect mistrust of scientific assurances about the safety of fluoridation. Ironically, public support for fluoridation seems to have fallen at the same time as caries rates in children have declined — in 1977, 90% of 12-year-old Australian children had caries, compared with 46% in 1994. Water fluoridation can’t take all the credit for this improvement, but a comparison of caries rates in Brisbane (the only capital city not to fluoridate water) with fluoridated Townsville highlights its important role. You have been asked to set up a new science project team for a biochemical company to manufacture a new wonder drug.

A. 6 minutes minutes

B. 8 minutes

C. 10 minutes

D.

11

SHORT ANSWER SECTION

LOW

Part Number Part Name

Advantage Nuclear Solar

Disadvantage

Fossil Fuels Hydro Electricity

marine environment and shoreline habitats Technology and the athlete: advances in designing racing bicycles Athletes can out race other mammals by using machines. Modern racing cycles can reach speeds of over 100 km/h. Technological advances in bicycle manufacture and increased understanding of air resistance and drag have enabled cyclists to reach new record speeds. A cycling race depends as much on the machine as it does on the athlete. One of the earliest bicycles was invented by Karl von Drais in Germany in 1817. It was called a Swiftwalker or Draisen. The frame was a wooden beam, the two wheels were wooden with leather tyres, and it had no pedals. The only time it picked up much speed was going downhill. In 1858 a bicycle with pedals was made. These pedalled bicycles became popular. Because they gave such a bumpy ride, due to their wooden or iron wheels, they were called boneshakers. In 1869 a slightly less bumpy bicycle was made with solid rubber tyres. A great breakthrough came in 1888-1889 when pneumatic (air-filled) rubber tyres were invented by John Dunlop. This made cycling more comfortable and faster. In the late 1800s, penny-farthings were popular. A penny-farthing had one large wheel at the front and a much smaller back wheel. The larger the front wheel, the longer the distance the cyclist would go with each turn of the pedals. They could go very fast over flat surfaces, but riding uphill was much harder. In the 1880s the safety bicycle was developed. It had a metal frame and two wheels of the same size. It was much safer and more stable than the penny-farthing. It had a chain-drive mechanism connecting the pedals to the back wheel. Today's racing bicycles have lighter frames and they are also more streamlined to increase aerodynamic efficiency. The standard spoked wheel creates a lot of drag. It behaves rather like an egg beater, making lots of small eddies (turbulence) as the tyre goes round. Disc wheels produce less drag and turbulence, but they are slightly heavier. When choosing material to make a bike frame inventors need to consider: Density-the heavier the material, the more force it will take to move. Elasticity-if something returns to its original shape after being bent or stretched it is said to be elastic, or have high elasticity. Yield strength-this is the amount of force required to bend a material so it is permanently bent (does not return to its original shape). Ultimate strength-the amount of force needed to break a material. The ultimate strength of materials used to make bicycle frames should be high in order to prevent the frame breaking during strenuous rides. Cost and availability. The materials used today are steel, aluminium, titanium and carbon fibre. Steel is cheapest, but heavy. A steel frame will bend well before it breaks but its yield strength is much lower. Also the

steel used for bikes is fairly elastic. Aluminium is light but brittle, and will only bend slightly before breaking. An aluminium frame breaks easily compared with a steel frame. Carbon fibre and titanium are light and fairly elastic, with a high ultimate strength and relatively low yield strength. They are also very expensive. Scientists are still searching for materials to make bike frames that are light, strong, cheap and fairly elastic. % abundance

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