Một người buộc một hòn đá vào đầu một sợi dây rồi quay dây trong mặt phẳng thẳng đứng. Hòn đá có khối lượng 0,4 kg chuyển động trên đường tròn bán kính 0,5 m với tốc độ không đổi 8 rad/s. Hỏi lực căng của dây khi hòn đá ở đỉnh của đường tròn ?

A. 8,88 N.                

B. 12,8 N.                

C. 3,92 N.                  

D. 15,3 N.

Reading 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

After two decades of growing student enrollments and economic prosperity, business schools in the United States have started to face harder times. Only Harvard's MBA School has shown a substantial increase in enrollment in recent years. Both Princeton and Stanford have seen decreases in their enrollments. Since 1990, the number of people receiving Masters in Business Administration (MBA) degrees, has dropped about 3 percent to 75,000, and the trend of lower enrollment rates is expected to continue

There are two factors causing this decrease in students seeking an MBA degree. The first one is that many graduates of four-year colleges are finding that an MBA degree does not guarantee a plush job on Wall Street, or in other financial districts of major American cities. Many of the entry-level management jobs are going to students graduating with Master of Arts degrees in English and the humanities as well as those holding MBA degrees. Students have asked the question, "Is an MBA degree really what I need to be best prepared for getting a good job?" The second major factor has been the cutting of American payrolls and the lower number of entry-level jobs being offered. Business needs are changing, and MBA schools are struggling to meet the new demands

As used in line 7, the word "seeking" could best be replaced by which of the following?

A. examining                 

B. avoiding           

C. seizing             

D. pursuing

Read the passage carefully and choose correct answer for each question below.

Education is another area of social life in which information technology is changing the way we communicate. Today's college students may not simple sit in a lecture or a library to learn about their field. Through their computers and the wonders of virtual reality they can participate in lifelike stimulated experiences. Consider the following scenario of the future of education made possible through developments in information technology.

For children over the age of 10, daily attendance at schools is not compulsory. Some of the older children attend school only once or twice a week to get tutorial support or instruction from a teacher. For the most part, pupils are encouraged to work online from home. Students should complete a minimum number of study hour per year; however, they may make up these hours by studying at home at times that suit their family schedule. They can log on early or late in the day and even join live classes in other countries. In order to ensure that each student is learning adequately, computer software will automatically monitor the number hours a week each student studies online as well as student's learning materials and assessment activities. Reports will be available for parents and teachers. The software can then identify the best learning activities and conditions for each individual student and generate similar activities. It can be also identify areas of weak achievement and produce special programs adjusted to the students' needs.

How many times are children who are older than 10 required to go to school weekly?

A. Three               

B. No time            

C. Once or twice  

D. Four

Hỗn hợp X gồm Na, Al, Mg. Tiến hành 3 thí nghiệm sau:

-Thí nghiệm 1: Hòa tan m gam X vào nước dư thu được V lít khí.

-Thí nghiệm 2: Hòa tan 2m gam X vào dung dịch NaOH dư thu được 3,5V lít khí.

-Thí nghiệm 3: Hòa tan 4m gam X vào dung dịch HCl dư thu được 9V lít khí.

-Các thể tích đều đo ở đktc và coi như Mg không tác dụng với nước và kiềm. Phát biểu nào sau đây là đúng?

A. Ở thí nghiệm 1, Al bị hòa tan hoàn toàn

B. Số mol Al gấp 1,5 lần số mol Mg

C. Phần trăm khối lượng của Na là 23,76%

D. Trong X có 2 kim loại có số mol bằng nhau

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the best answer for each question from 40 to 47.

        Cooking shows on TV are usually all about exotic foods. Thank to globalization, people everywhere are introducing their taste buds to dishes from every corner of the world. At the same time, other people are discovering that food from their area is the best kept secret. In the past few years, this movement of purchasing local produce keeps picking up steam because it offers a lot of benefits. For starters, local food is often tastier because it is fresher. Goods that are imported from abroad must be flown or shinped in from far away, so they naturally lose some of their freshness during the journey. A simple way to test this is to sample a banana from overseas versus one that was grown locally and compare the tastes. Imported goods must also be washed and packaged in plastic or other containers so they can survive the journey. These materials may cause the nutritional value of these goods to decline during the shipping process. Food safety is another reason why people are choosing local produce. Today's laws regarding foods vary from country to country. This causes confusion and makes it difficult to detect if any harmful pesticides were used. When you know the local farmer who grows your food and the fields that are used to produce it, the chances of it being contaminated are greatly reduced.

        Buying local foods can also have beneficial impact on the environment. By supporting local growers, consumers can maintain green space and farmland in their communities. Buying locally also helps to build the local community. If farmers can sell directly to consumers instead of a middleman, they will earn more money for their families. Additional profits also enable farmers to better care for their soil and keep quality standards high. In the end, it is a win-win situation for both parties.

      If you are interested in incorporating more local foods into your diet, you can start by attending a farmers' market in your area. This is an open market where farmers sell fruits, vegetables, and meat directly to the public. If you have any questions about the production process or quality of these goods, you can ask the farmers directly. Once you experience the freshness of local foods for yourself, it might be tough to go back to the supermarket.

The phrase “picking up steam” in paragraph 1 can be ___________.

A. running out of

B. changing unexpectedly

C. decreasing rapidly

D. working effectively