user-avatar
nthuyentrang
2 năm trước
Một vật có khối lượng 2kg nằm yên trên sàn nhà tại A thì được kéo bằng một lực theo phương nằm ngang và có độ lớn 4N nhv, biết trên đoạn AB không có ma sát. Lấy g= 10m/s2. a. Tính gia tốc trên đoạn AB? b. Tính thời gian vật đi quãng đường AB? Biết AB=9m. c. Khi đến B lực kéo ngừng tác dụng vật chuyển động chầm dần đều và dừng lại tại C cách A 8m. Tính hệ số ma sát trên đoạn BC? Muốn trên đoạn BC vật chuyển động thẳng đều thì khi đến B phải tăng hay giảm bao nhiêu?
Thích Trả lời Chia sẻ

Các câu hỏi liên quan

THE QUALITIES WE PRIZE IN OUR CHILDREN​ A recent international study has shown some surprising and apparently contradictory results on the question of the priorities parents around the world have when raising their children. While the survey showed that some virtues are universally prized, interesting regional and national trends emerge wrhen parents are asked to rate the importance of various qualities they wish to instil in their children. Parents around the world seem to agree that good manners, a sense of responsibility and respect for others are important qualities to teach their children. But while West Europeans give all three qualities more or less equal importance, East Europeans and North Americans rate a sense of responsibility as by far the most important, and relegate respect for others to fourth place. Interestingly, a sense of imagination ranked the lowest priority worldwide, although West Europeans gave the quality of flexible thinking twice the importance any other group did. The Italians stress the virtue of cultivating their youngsters' imagination more than most others surveyed, with the exception of Switzerland. The supposedly staid Swiss prize imaginative youth. Etiquette-minded Belgians, Spaniards and Greeks placed the highest premium on politeness, while the Danes and Swedes put good manners lowest on the list. The newly-capitalist Eastern bloc countries also rated good manners as relatively unimportant, perhaps because they are being confronted with commercial competition for the first time. Together with the Swiss and the Turks, on the other hand, they prized the ability to communicate with others. The virtues of tolerance and respect for others were most highly regarded in Scandinavia, France, Britain, Switzerland, the Netherlands and Spain. This was not the case in Greece and the former Eastern bloc nations, which rated these as being of lesser importance. Germans, Austrians and Swedes esteem personal independence, but the industrious French hold the quality of conscientiousness at work more dear than any other European nationals. The responses in the industrialized nations of Sweden and Britain showed, perhaps bewilderingly, that nationals of those countries gave little importance to conscientiousness at work. Polite Belgians answered that for them, obedience is among their paramount values; this sentiment is shared to a lesser degree by the British, Greeks and Irish. The Italians, according to their questionnaires, ranked this very low. When rearing their children, the Greeks, Turks and Irish are alone in their emphasis on instilling strong religious beliefs. One of the primary difficulties the researchers faced was translating the questions as perfectly as possible in order not to distort the result. "Imagination", for example, can be translated into Dutch as "conceited-ness''; perhaps this explains why the Dutch appeared to give imagination a low priority. Also, some qualities are so ingrained in certain cultures that they are taken for granted, while others are given great emphasis because thev are felt to be lacking in a particular society 1. The survey shows that ..... A. some values are general and others vary. B. no patterns emerged. C. different nations contradict each other. D. there are no clear results. 2. For the North Americans, a sense of responsibility is .... A. more important than it is for East Europeans. B. more important than respect for others. C. as important as it is for West Europeans. D. as important as respect for others. 3. A sense of imagination is ..... A. most important to the Italians. B. most important to the Swiss. C. important to all except the Swiss. D. equally important to the Italians and the Swiss. 4. Politeness is less important in the Eastern bloc because .... A. they enjoy confrontation. B. they are competitive people. C. they are still getting used to capitalism. D. they are relatively uncommunicative. 5. "They" (underlined) in paragraph 4 refers to.... A. commercial competitors. B. the Swiss and Turks. C. good manners. D. Eastern bloc countries. 6. Although their societies are industrialized, the British and Swedes.... A. are not conscious of it. B. are bewildered by industry. C. do not think hard work important. D. do not think their nationality important. 7. The research was difficult because ..... A. the researchers made so many mistakes. B. the results were distorted. C. no one knew how to translate certain words. D. it had to be conducted in so many languages.

2018 © Loga - Không Ngừng Sáng Tạo - Bùng Cháy Đam Mê
Loga Team