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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.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

The word “volume” in the passage refers to ______.

A. loudness

B. quantity

C. frequency

D.  lenght

1
27 tháng 3 2018

Đáp án B

B. quantity: từ “quantity” có nghĩa là “số lượng”.

Cụm từ “a volume of water” trong đoạn hai có nghĩa là “một lượng nước”.

Câu A “loudness” có nghĩa là “độ lớn của âm thanh”.

Câu C “frequency” có nghĩa là “tần suất”.

Câu D “length” có nghĩa là “độ dài”.

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....
Đọc tiếp

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 cmis 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.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

Archimedes’ Principle explains why ____

A. all objects will float

B. Archimedes became 

C. objects seem lighter in water

D. humans can swim

1
22 tháng 6 2019

Đáp án C

C. objects seem lighter in water: Định lí Archimedes giải thích tại sao: các vật thể có thể nhẹ hơn nước.

Chúng ta có thể tìm thấy ý này trong câu hai của đoạn một : “The principle is most frequently applied….and why objects seem lighter in water”.

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....
Đọc tiếp

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 cmis 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.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

The word “upthrust” in the passage refers to the _____

A. upward push

B. upper side of an object

C. upturned force

D. upside-down turn

1
31 tháng 7 2019

Đáp án A

A. upward push: từ “upthrust” trong đoạn bốn đề cập đến “lực đẩy từ dưới lên = upward push”.

Còn các đáp án khác

Câu B “upperside of an object”: phía bên trên của một vật.

Câu C “upward force”: lực làm lật tàu, thuyền.

Câu D “upside-down turn”: việc lật lại từ trên xuống dưới.

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....
Đọc tiếp

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 cmis 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.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

What happens when something is immersed in a fluid?

A. It will be pushed further down with a force, equal to the weight of the fluid displaced.

B. It receives an upward force, equal to the weight of the fluid displaced

C. It receives a download force, equal to the weight of the fluid displaced

D. The fluid will expand the object and overflow to the floor

1
26 tháng 5 2018

Đáp án B

It receives an upward force, equal to the weight of the fluid displaced: “Nó nhận một lực đẩy lên tương đương với trọng lượng của chất lỏng bị chiếm chỗ”.

Câu này thích hợp với câu hỏi: “Điều gì xảy ra khi một vật nào đó nổi lên trong một chất lỏng?”

Chúng ta có thể tìm thấy ý này trong câu đầu của đoạn một: “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.”

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....
Đọc tiếp

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 cmis 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.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

A block of wood with a density seven tenths that of water will ____

A. go up and down the sink

B. float with a half of its volume under water

C. float with an equal volume of its volume under water

D. sink immediately when submerged

1
26 tháng 2 2019

Đáp án C

C. float with an equal volume of its volume under water

Ý nghĩa của cả câu: “Một khối gỗ có tỉ trọng bảy phần mười tỉ trọng của nước sẽ nổi lên với một thể tích tương đương với thể tích chìm của nước”.

Chúng ta có thể tìm thấy ý này trong câu ba của đoạn 3: “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 displaces is the same as the block’s own weight”.

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....
Đọc tiếp

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 cmis 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.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

The word “displaces” in the passage almost means “_____”

A. takes the place of        

B. takes place

C. replaces with a new one

D. puts in position

1
17 tháng 8 2019

Đáp án A

A. takes the place of: động từ “displaces” trong đoạn ba có nghĩa là “chiếm chỗ của”.

Còn các đáp

Câu B “takes places” có nghĩa là “xảy ra”.

Câu C “replaces with a new one = thay thế bằng một cái mới”, không đúng với ý nghĩa trong câu.

Câu D “puts in position” có nghĩa là “đặt vào vị trí”.

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....
Đọc tiếp

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 cmis 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.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

Ships cannot be so heavily loaded if they want to sail in fresh water as they sail in the sea, because ____

A. fresh water is ‘lighter’ than sea water

B. there’s too much salt in sea water 

C. sea water is ‘saltier’ than fresh water

D. fresh water is more polluted

1
13 tháng 12 2019

Đáp án A

A. fresh water is ‘lighter’ than sea water: ý nghĩa của cả câu này là “Tàu thuyền không thể được chất nặng khi chúng đi trên sông như khi chúng đi trên biển, bởi vì nước sông thì nhẹ hơn nước biển”.

Chúng ta có thể tìm thấy ý này trong câu hai của đoạn bốn: “In addition, they cannot be so heavily loaded….to give the necesssary upthrust”

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....
Đọc tiếp

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 cmis 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.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

A ship floats, whereas a block of iron of the same mass sinks because the ship ____

A. is made of wood

B. is lighter

C. has buoys 

D. has a special shape

1
5 tháng 5 2019

Đáp án D

D. has a special shape: ý nghĩa cả câu này: “Một chiếc tàu nổi bềnh bồng trong khi một khối sắt có trọng lượng giống như thế thì chìm bởi vì chiếc tàu có hình dáng đặc biệt”.

Chúng ta có thể tìm thấy ý này trong hai câu cuối của đoạn 3: “If a dense material is made into a suitable shape, it will float because of Archimedes’ principle. A ship floats, whereas a block of iron of the same mass sinks”.

Mark the letter a, B, C, or D on your answer sheet to indicate the sentence that is closest meaning to each of the following questions or indicate the correct answer to each of them from 1 to 8 Tsunami is a Japanese word which means harbor wave and is used as the scientific term for seismic sea wave generated by an undersea earthquake or possibly an undersea landslide or volcanic eruption. When the ocean floor is tilted or offset during an earthquake, a set of waves is created similar to the...
Đọc tiếp

Mark the letter a, B, C, or D on your answer sheet to indicate the sentence that is closest meaning to each of the following questions or indicate the correct answer to each of them from 1 to 8

Tsunami is a Japanese word which means harbor wave and is used as the scientific term for seismic sea wave generated by an undersea earthquake or possibly an undersea landslide or volcanic eruption. When the ocean floor is tilted or offset during an earthquake, a set of waves is created similar to the concentric waves generated by an object dropped into the wave. Most tsunamis originate along the Ring of Fire, a zone of volcanoes and seismic activity, 32.500 km long that encircles the Pacific Ocean. Since 1819, about 40 tsunami have struck the Hawaiian Islands.

A tsunami can have wave lengths, or widths, of 100 to 200 km, and may travel hundreds of kilometres across the deep ocean, reaching speeds of about 725 to 800 kilometres an hour. Upon entering shallow coastal waters, the wave, which may have been only about half a metre high out at sea, suddenly grows rapidly. When the wave reaches the shore, it may be 15 metres high or more. Tsunamis have tremendous energy because of the great volume of water affected. They are capable of obliterating coastal settlements.

Tsunami should not be confused with storm surges, which are domes of water that rise underneath hurricanes or cyclones and cause extensive coastal flooding when the storms reach land. Storm surges are particularly devastating if they occur at high tide. A cyclone and accompanying storm surge killed an estimated 500,000 people in Bangladesh in 1970. The tsunami which truck south and southeast Asia in late 2004 killed over 200 thousand people.

What will happen when an object is dropped into the water?

A. Volcanic eruption may be a consequence

B. Some concentric waves will be generated

C. There will be seismic activity

D. Earthquake may happen

1
17 tháng 8 2018

Đáp án B

Điều gì sẽ xảy ra nếu có 1 vật thể rơi vào trong nước:

A. Hậu quả có thể là 1 vụ phụ trào núi lửa.

B. Một số vòng sóng đồng tâm sẽ được tạo ra.

C. Hoạt động địa chấn sẽ xảy ra.

D. Động đất có thể xảy ra

Dẫn chứng ở câu thứ 2 đoạn 1: “a set of waves is created similar to the concentric waves generated by an object dropped into the wave” – ( một loạt các con sóng được tạo ra tương tự như các vòng sóng đồng tâm được hình thành khi ta thả 1 vật thể xuống nước ).

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 from 43 to 50.          Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a...
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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 from 43 to 50.

         Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a radioactive substance such as carbon-14 has a known half-life, the amount of carbon-14 remaining in an object can be used to date that object.

        Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14. It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-14, this indicates that around half of the carbon-14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old.

        Carbon dating cannot be used effectively in dating objects that are older than 80,000 years. When objects are that old, much of the carbon-14 has already decayed into nitrogen-14, and the miniscule amount that is left doesn’t provide a reliable measurement of age. In the case of older objects, other age-dating methods are available, methods which use radioactive atoms with longer half-lives than carbon has.

It can be inferred from the passage that if an item contains more carbon-14 than nitrogen-14, then the item is _______.

A. not as much as 5,570 years old

B. too old to be age-dated with carbon-14

C. too radioactive to be used by archeologists

D. more than 5.570 years old

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31 tháng 1 2018

Đáp án A.

Có thể suy ra từ đoạn văn rằng nếu một vật có chứa nhiều các-bon 14 hơn ni-tơ 14, thì vật đó_____                     

A. không đến 5.570 năm tuổi

B. quá lâu đời đ có thế xác định được niên đại với carbon-14

C. chứa quá nhiều phóng xạ để được sử dụng bởi các nhà khảo cổ.

D. trên 5.570 năm tui.

Dựa vào đoạn 2: “Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14. It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-lá, this indicates that around half of the carbon- 14 has decayed into nitrogen-14, and the sample is approximately 5.570 years old”: Carbon-14 có thời gian bán hủy 5,570 năm, nghĩa là sau từng ấy năm, một nửa các nguyên tử carbon-14 đã bị phân hủy thành nitơ-14. Chính tỷ lệ carbon-14 có trong chất đó cho thấy độ tuổi của nó. Thí dụ như, nếu trong một mẫu vật cụ thể lượng cacbon-14 tương đương với lượng nitơ- 14, điều đó chỉ ra rằng khoảng một nửa lượng carbon- 14 đã phân hủy thành nitơ-14, và mẫu vật đó có niên đại khoảng 5,570 tui.

Nếu một vật có chứa nhiều các-bon 14 hơn ni-tơ 14, thì chứng tỏ nó chưa hoàn tất chu kì bán hủy của mình kéo dài trong 5.570 năm nên vật đó chưa tới 5.570 tuổi.