What invisible force holds you onto the earth, so that you don't simply fall off?
Answer: A
Gravity holds you to the earth - the mutual attraction between any two masses.
At the surface it gives everything an acceleration of about 9.8 m/s² towards the centre, and your weight is simply that acceleration multiplied by your mass.
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Glass is made of the mixture of
Answer: A
Glass is made from sand and silicates - silica fused with sodium carbonate and limestone.
The soda lowers silica's melting point from about 1,700°C to a workable temperature, and the lime stops the product dissolving in water. The mixture cools to a rigid but non-crystalline solid.
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Persons with which blood group are called universal donors?
Answer: C
People with blood group O negative are called universal donors.
Their red cells carry neither A nor B antigen, so they provoke no reaction in a recipient of any group. Group AB is the universal recipient for the opposite reason: it has no anti-A or anti-B antibodies in the plasma.
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Which one of the following types of laser is used in laser printers?
Answer: A
Laser printers use a semiconductor laser - a laser diode.
It is small, cheap, efficient and can be switched on and off millions of times a second, which is what is needed to write a page of dots onto the photosensitive drum.
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Which of the following is not an intensive property?
Answer: A
Weight is not an intensive property. It depends on how much material there is, which makes it extensive.
Density, refractive index and melting point are intensive: they are the same for a drop of water as for a lake of it.
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Plants mainly receive their nutrients from
Answer: B
Plants take their mineral nutrients from the soil, absorbing nitrogen, phosphorus, potassium and the micronutrients in solution through the root hairs.
Sunlight provides energy and chlorophyll captures it, but neither is a nutrient; the carbon comes from the air as carbon dioxide.
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The first synthetic fibre made by man was ____ ?
Answer: D
Nylon was the first fully synthetic fibre, developed by Wallace Carothers at DuPont and put on sale in 1938.
It is built from small molecules rather than from a natural polymer. Rayon came earlier but is regenerated cellulose, so it is not fully synthetic.
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The hardest material available on earth is
Answer: B
Diamond is an allotrope of carbon. Every atom is bonded to four others in a rigid tetrahedral network, which is what makes it the hardest natural substance.
Graphite, charcoal and the fullerenes are the other allotropes; they differ only in how the same atoms are arranged.
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Which of the following metals forms an amalgam with other metals ?
Answer: A
Mercury forms amalgams. An amalgam is simply an alloy of mercury with another metal, and mercury will dissolve gold, silver, zinc, sodium and many others at room temperature.
Dental amalgam is mercury with silver and tin; extracting gold by amalgamation exploits the same property.
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A man who is a specialist in wine making is called
Answer: C
A specialist in wine-making is an oenologist, from the Greek oinos, wine.
Oenology covers everything after the grapes are picked - fermentation, ageing and blending. Growing the vines is viticulture.
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