Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
Archimedes’s Principle is a law of physics that states that when an object is totally or partially immersed in a fluid, it experiences an upthrust equal to the weight of the fluid displaced. The principle is most frequently applied to the behaviour of objects in water, and helps to explain floating and sinking, and why objects seem lighter in water. It also applies to balloons.
The key word in the principle is “upthrust”, which refers to the force acting upward to reduce the apparent weight of the object when it is under water. If, for example, a metal block with a volume of 100 cm3 is dipped in water, it displaces an equal volume of water, which has a weight of approximately 1 N (3.5 oz). The block therefore seems to weigh about 1 N less.
An object will float if its average density is less than that of water. If it is totally submerged, the weight of the water it displaces (and hence the upthrust on it) is greater than its own weight, and it is forced upward and out of water, until the weight if water displaced by submerged part is exactly equal to the weight of the floating object. Thus a block of wood with a density six tenths that of water will float with six tenths of its volume under water, since at that point the weight of fluid displaced is the same as the blocks’s own weight. If a dense material is made into a suitable shape, it will float because of Archimedes’s principle. A ship floats, whereas a block of iron of the same mass sinks.
It is also because of Archimedes’s principle that ships float lower in the water when they are heavily loaded (more water must be displaced to give the necessary upthrust). In addition, they cannot be so heavily loaded if they are to sail in fresh water as they can if they are to sail in the sea, since fresh water is less dense than sea water, and so more water must be displaced to give the necessary upthrust. This means the ship is lower in the water, which can be dangerous in rough weather.
A ship floats, whereas a block of iron of the same mass sinks because the ship
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Lời giải:
Báo saiThông tin: In a raid, several thousand Polyergus workers will travel up to 500 feet in search of a Formica nest, penetrate it, drive off the queen and her workers, capture the pupal brood, and transport it back to their nest.
Dịch nghĩa: Trong một cuộc đột kích, hàng ngàn kiến thợ Polyergus sẽ di chuyển lên đến 500 feet để tìm kiếm một tổ Formica, thâm nhập nó, bắt hoàng hậu và công nhân của cô, bắt nhộng, và vận chuyển nó trở lại tổ của chúng.
Như vậy phương án B. Raid another nest = đột kích một tổ kiến khác là phương án chính xác nhất.
A. Look for food = tìm thức ăn
Care for the young = chăm sóc con trẻ
Clean its own nest = làm sạch tổ của chúng