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• Công của trọng lực trong 2 giây cuối khi vật có khối lượng 8kg được thả rơi từ độ cao 180m là bao nhiêu? Lấy g = 10m/s2

Câu 1:

Công của trọng lực trong 2 giây cuối khi vật có khối lượng 8kg được thả rơi từ độ cao 180m là bao nhiêu? Lấy g = 10m/s2

A.

8000J        

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Phân tích:  + Thời gian rơi của vật khi được thả rơi từ độ cao 180 m    Quãng đường đi trong 4s đầu: .10.42 = 80(m) Khi đi được 4s đầu thì vật đang ở độ cao 100m vậy công của trọng lực trong 2 giây cuối → Ap = mg.h = 8.10.100 = 8000 (J)    

B.

7000J

C.

6000J        

D.

5000J

Những câu hỏi này đến từ bài kiểm tra này. Bạn có muốn thực hiện bài kiểm tra thử không?

Bài tập trắc nghiệm 15 phút Công và công suất - Định luật bảo toàn - Vật Lý 10 - Đề số 10

• 15 phút
• 10 câu hỏi

Làm bài kiểm tra

Một số câu hỏi từ cùng một bài kiểm tra

• Công thức tính công của một lực là

• Một học sinh của trung tâm bồi dưỡng kiến thức Hà Nội nâng tạ có khối lượng 80kg lên cao 60cm trong t = 0,8s. Trong trường hợp học sinh đã hoạt động với công suất là bao nhiêu? Lấy g = 10m/s2

• Đơn vị đo công suất của nước Anh được kí hiệu là HP. Nếu trên một chiếc máy lạnh có ghi 2 HP thì công suất của máy là

• Công của trọng lực trong 2 giây cuối khi vật có khối lượng 8kg được thả rơi từ độ cao 180m là bao nhiêu? Lấy g = 10m/s2

• Cho rằng bạn muốn đi lên đồi dốc đứng bằng xe đạp leo núi. Bản chỉ dẫn có 1 đường, đường thứ nhất gấp 2 chiều dài đường kia. Bỏ qua ma sát, nghĩa là xem như bạn chỉ cần “chống lại lực hấp dẫn”. So sánh lực trung bình của bạn sinh ra khi đi theo đường ngắn và lực trung bình khi đi theo đường dài là:
• Một động cơ có công suất không đổi, công của động cơ thực hiện theo thời gian là đồ thị nào sau đây?  

• Một vật khối lượng 8kg được kéo đều trên sàn bằng 1 lực 20N hợp với phương ngang 1 góc α= 30° .Khi vật di chuyển lm trên sàn, lực đó thực hiện được công là:  

• KWh là đơn vị của
• Biểu thức tính công là
• Chọn câu sai khi nói về công của một vật:

Một số câu hỏi khác bạn có thể quan tâm

• Read the following passage and mark the fetter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 35.

  Facebook users spend an average of more than 15 hours a month on the social networking site. While there are plenty who caution against such intensive use — and there are a number of studies detailing the harm Facebook could potentially cause — there also are lots of reports extolling the site's virtues. As the social media giant prepares for its upcoming initial public offering, here are some ways Facebook just might be good for you.

  Spending time on Facebook can help people relax, slow down their heart rate and decrease stress levels, according to researchers from the Massachusetts Institute of Technology and the University of Milan. In a study published earlier this year, researchers studied 30 students and found that a natural high was sparked when they were on the social media network that led to the relaxed heart rates and lower levels of stress and tension. In the study, the students were monitored in three situations: looking at panoramic landscapes, performing complicated mathematical equations and using Facebook. While the first situation was the most relaxing to students and the math problems were the most stressful, the time on Facebook uncovered high levels of attractiveness and arousal. The findings support the researchers' hypothesis that Facebook's success, as well as that of other social media networks, correlates to the specific positive mental and physical state users experience.

  While many may argue that social media networks only distract employees, research shows the opposite may be true. Research from Keas.com found that a 10-minute Facebook break makes employees happier, healthier and more productive. The study examined workers in three groups: one that was allowed no breaks, one that was allowed to do anything but use the Internet and one that was allowed 10 minutes to use the Internet and Facebook. The Facebook group was found to be 16 percent more productive than the group that was not allowed to use the Internet and nearly 40 percent more productive than the group that was allowed no breaks. "Short and unobtrusive breaks, such as a quick surf on the Internet, enables the mind to rest itself, leading to a higher net total concentration for a day's work, and as a result, increased productivity," said Brent Coker of the department of management and marketing at the University of Melbourne in Australia.

  Facebook is also in the business of matchmaking. Research shows that nearly 60 percent of singles will friend someone new on Facebook after meeting them in person. If they like what they see, 25 percent are likely to contact their new love interest via Facebook. Once the courting is over, nearly 40 percent of those social networking adults will update their relationship status on Facebook, with just 24 percent telling their friends first. Facebook use between couples will continue through the dating process, the research shows. Throughout the day, 79 percent of couples said they send partners Facebook messages or chat on the social network. In addition, more than 60 percent would post romantic messages on their significant other's Facebook wall. When the relationship ends, more than half of those surveyed immediately update their status to single, which automatically sends out a notification to their friend list to start the dating cycle over again.

  Which of the following could best describe the tone of the passage?

• Đọc đoạn văn và trả lời câu hỏi. Children may drink or eat chemical and drug (because they look like soft drink or candy), if we don’t put all these things in locked cupboard. The kitchen is a dangerous place so we mustn’t let children play in the kitchen. Playing with matches is also very dengerous because it only take one match to cause a fire. We must cover electrical sockets because electricity can easily kill. We have to keep all dangerous object out of children reach. These include scissors, knives, and small objects such as beads. A. Trả lời True (T) hoặc False (F).

  ___ Playing with a match can start a fire.

• Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

  Children are expected to make the right thing both at school and at home.

• Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.

  The agreement ended six-month negotiation. It was signed yesterday

• Generic medications are just as ______________, and much less expensive.

• Read the following passage and mark the letter A,B,C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

  A trend that has emerged recently is the sharing of childcare (1) __________ between husband and wife. Young couples will try to arrange their work schedules so that they work opposite hours or shifts in order that one parent is always home with the children. Since childcare is expensive, this saves money for the young couple trying to establish themselves and provide a secure environment for the family. Husband and wife may also share household chores. Some fathers are just as capable as mothers at cooking dinner, changing and bathing the baby, and doing the laundry.

  In some cases, the woman’s salary is for family (2) __________ and the father becomes the “househusband." These cases are still fairly rare. One positive trend, however, is that fathers seem to be spending more time with their children. In a recent survey, 41% of the children sampled said they spend equal time with their mothers and fathers. “This is one of our most significant cultural changes,” says Dr. Leon Hoffman, who co-directs the Parent Child Center at the New York Psychoanalytic Society. In practice, for over 30 years, Hoffman has found "a very dramatic difference in the involvement of the father in everything from care-taking to general decision (3) __________ around kids' lives.”

  Another factor has recently been added to the childcare formula. The number of people who work from home nearly full-time rose 23% from the last decade. The (4) _________ of technology - computers, faxes, teleconferencing - has made it easier for at-home workers to be constantly in touch. Will this new flexibility in the workforce bring a positive change for the (5) __________ of children? Only time will tell.

  Điền vào ô 3.