Ví dụ về hiện tượng hàng rào cách li sau hợp tử là:

Dao động tắt dần là một dao động có:  

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.

People used to know more or less how their children would live. Now things are changing so quickly that they don’t even know what their own lives will be like in a few years’ time. What follows is not science fiction. It is how experts see the future. You are daydreaming behind the steering wheel; is it too dangerous? No! That’s no problem because you have it on automatic pilot, and with its hi–tech computers and cameras, your car “know” how to get you home safe and sound. What is for lunch? In the old days you used to stop off to buy a hamburger or a pizza. Now you use your diagnostic machine to find out which foods your body needs. If your body needs more vegetables and less fat, your food–preparation machine makes you a salad. After lunch, you go down the hall to your home office. Here you have everything you need to do your work. Thanks to your information screen and your latest generation computer, you needn’t go to the office anymore. The information screen shows an urgent message from a co-worker in Brazil. You can instantly send back a reply to him and go on to deal with other matters.

Question: Which of the following is NOT true about life in the future?          .  

Chọn đáp án sai khi nói về dao động cưỡng bức:

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.

People used to know more or less how their children would live. Now things are changing so quickly that they don’t even know what their own lives will be like in a few years’ time. What follows is not science fiction. It is how experts see the future. You are daydreaming behind the steering wheel; is it too dangerous? No! That’s no problem because you have it on automatic pilot, and with its hi–tech computers and cameras, your car “know” how to get you home safe and sound. What is for lunch? In the old days you used to stop off to buy a hamburger or a pizza. Now you use your diagnostic machine to find out which foods your body needs. If your body needs more vegetables and less fat, your food–preparation machine makes you a salad. After lunch, you go down the hall to your home office. Here you have everything you need to do your work. Thanks to your information screen and your latest generation computer, you needn’t go to the office anymore. The information screen shows an urgent message from a co-worker in Brazil. You can instantly send back a reply to him and go on to deal with other matters.

Question: What is “reply” CLOSEST in meaning to?         

Dao động tắt dần:

Phát biểu nào sau đây là đúng khi nói về dao động tắt dần?

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.

People used to know more or less how their children would live. Now things are changing so quickly that they don’t even know what their own lives will be like in a few years’ time. What follows is not science fiction. It is how experts see the future. You are daydreaming behind the steering wheel; is it too dangerous? No! That’s no problem because you have it on automatic pilot, and with its hi–tech computers and cameras, your car “know” how to get you home safe and sound. What is for lunch? In the old days you used to stop off to buy a hamburger or a pizza. Now you use your diagnostic machine to find out which foods your body needs. If your body needs more vegetables and less fat, your food–preparation machine makes you a salad. After lunch, you go down the hall to your home office. Here you have everything you need to do your work. Thanks to your information screen and your latest generation computer, you needn’t go to the office anymore. The information screen shows an urgent message from a co-worker in Brazil. You can instantly send back a reply to him and go on to deal with other matters.

Question: What is the main idea of the passage?          

Dao động cưỡng bức có biên độ càng lớn khi

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:

Studies about how students use their time might shed light on whether they face increased academic and financial pressures compared with earlier eras. Based on data about how students are spending time, academic or financial pressures don’t seem to be greater now than a generation ago. The data show that full-time students in all types of colleges study much less now than they did a generation ago–a full 10 hours a week less. Students are also receiving significantly higher grades. So it appears that academic pressures are, in fact, considerably lower than they used to be. The time–use data don’t suggest that students feel greater financial pressures, either. When the time savings and lower opportunity costs are factored in, college appears less expensive for most students than it was in the 1960s. and though there are now full-time students working to pay while in college, they study less even when paid work choices are held constantly. In other words, full-time students do not appear to be studying less in order to work more. They appear to be studying less and spending the extra time on leisure activities or fun. It seems hard to imagine that students feeling increased financial pressures would respond by taking more leisure. Based on how students are spending their time then, it doesn’t look as though academic or financial pressures are greater now than a generation ago. The time-use data don’t speak directly to social pressures, and it may well be that these have become more intense lately. In one recent set of data, students reported spending more than 23 hours per week either socializing with friends or playing on the computer for fun. Social activities, in person or on computer would seem to have become the major focus of campus life. It is hard to tell what kinds of pressures would be associated with this change.  

Question: The author finds it hard to point out__________         

Biên độ dao động khi có sự cộng hưởng cơ phụ thuộc vào: