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.
Ships cannot be so heavily loaded if they want to sail in fresh water as they sail in the sea, because .
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Lời giải:
Báo saiThông tin: The true extent of the Polyergus ants' dependence on the Formica becomes apparent when the worker population grows too large for existing nest. Formica scouts locate a new nesting site, return to the mixed- species colony, and recruit additional Formica nest mates. During a period that may last seven days, the Formica workers carry to the new nest all the Polyergus eggs, larvae, and pupae, every Polyergus adult, and even the Polyergus queen.
Dịch nghĩa: Mức độ thực sự của sự phụ thuộc của kiến Polyergus đối với kiến Formica trở nên rõ ràng khi dân số lao động trở nên quá lớn cho tổ hiện có. Kiến do thám Formica xác định vị trí làm tổ mới, trở về lãnh địa của hỗn hợp các loài, và tuyển dụng thêm bạn cùng tổ Formica. Trong thời gian có thể kéo dài bảy ngày, các công nhân Formica mang về tổ mới tất cả các trứng của Polyergus, ấu trùng và nhộng, mỗi kiến trưởng thành Polyergus, và thậm chí cả nữ hoàng Polyergus.
Phương án D. The Polyergus and the Formica move to a new nest = Kiến Polyergus và Formica di chuyển đến một tổ mới, là phương án chính xác nhất.