Hai quả cầu nhỏ giống nhau, mỗi vật thừa một electron. Tìm khối lượng mỗi quả cầu để lực tĩnh điện bằng lực hấp dẫn giữa chúng. Cho G = 6,67.10^-11 m³/kg.s

Nguời ta thiết kế một cái tháp gồm \(10\) tầng theo cách: Diện tích bề mặt trên của mỗi tầng bằng nửa diện tích bề mặt trên của tầng ngay bên dưới và diện tích bề mặt của tầng \(1\) bằng nửa diện tích bề mặt đế tháp. Biết diện tích bề mặt đế tháp là \(12\,288\) m\({{}^{2}}\), tính diện tích bề mặt trên cùng của tháp (đơn vị mét vuông).

Cho chóp tứ giác đều S.ABCD có tất cả các cạnh bằng a.

Đường thẳng SA vuông góc với

Many diseases that were once considered fatal are now _______ with advanced medical treatments.

Read the following passage about climate change and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions from 23 to 30. (2 points)

       Vietnamese cultural identity is a rich and intricate tapestry that reflects the nation’s long and storied history. Rooted in over a thousand years of civilization, Vietnam’s cultural identity is a fusion of indigenous traditions and external influences, shaped by its geographical location and historical interactions.

         First and foremost, at the heart of Vietnamese culture is a deep reverence for family and community. Confucian values emphasizing respect for elders, filial piety, and social harmony have played a pivotal role in shaping Vietnamese society. These values are reflected in the close-knit family structures, hierarchical relationships, and communal rituals that are integral to daily life.

         Secondly, Vietnamese cuisine is celebrated worldwide for its exquisite flavors and diversity. With its emphasis on fresh ingredients, fragrant herbs, and balanced flavors, Vietnamese food tells a story of the country’s agricultural heritage and regional variations. Iconic dishes like pho, banh mi, and spring rolls have become global favorites, representing the culinary artistry deeply ingrained in Vietnamese culture. Also, Vietnam’s artistic expressions are equally captivating. Traditional art forms like water puppetry, silk painting, and folk music continue to thrive alongside contemporary artistic movements. Áo dài, a graceful traditional dress, exemplifies the fusion of elegance and modesty in Vietnamese fashion, symbolizing cultural pride and identity.

         Today, in the face of modernization and globalization, Vietnamese cultural identity remains resilient. While adapting to the challenges of the 21st century, the Vietnamese people continue to honor their traditions, celebrate their unique cultural expressions, and pass on their heritage to future generations, ensuring that their cultural identity remains vibrant and enduring.

In which paragraph does the writer state that Vietnamese cultural identity is influenced by both internal and external factors?

Cho hai số phức $z_1=-3+2i$ và $z_2=1-i$. Phần ảo của số phức $\overline{z_1}+z_2$ bằng?

Read the following passage about the future of energy and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions.

     [I] As the world grapples with the finite nature of fossil fuel reserves and the detrimental impact of climate change, the future of energy undeniably lies in renewable sources. [II] Scientists and engineers are making substantial advancements in the development of technologies that more efficiently harness solar, wind, hydro, and geothermal energy. [III] Although the transition to these renewable sources presents significant challenges, it is also regarded as a pivotal step towards establishing a sustainable and resilient energy system. [IV]

     One of the most promising advancements in renewable energy is the enhancement of solar panel efficiency. Progress in photovoltaic technology has led to the creation of panels that convert a higher proportion of sunlight into electricity. Likewise, wind turbines are becoming more and more efficient. They are capable of generating power even under low-wind conditions. These innovations are essential for making renewable energy more feasible and accessible to a broader population.

     However, the transition to renewable energy is fraught with obstacles. The intermittent nature of sources like solar and wind necessitates reliable storage solutions to ensure a consistent power supply. Although battery technology has seen significant improvements, further advancements are imperative to meet growing demand. Moreover, new infrastructure for distributing renewable energy requires expansion and upgrading to accommodate these new power sources.

     The economic impact of transitioning to renewable energy is another critical consideration. While the initial investment in renewable energy infrastructure can be substantial, the long-term benefits include reduced energy costs and job creation in the green energy sector. Governments and private enterprises are increasingly acknowledging the necessity of investing in renewable energy projects, which is crucial for fostering innovation and diminishing reliance on fossil fuels.

     Ultimately, the future of energy hinges on our capacity to innovate and adapt. By continuing to invest in research and development, improving infrastructure, and addressing economic and technical challenges, we can transition towards a more sustainable and environmentally friendly energy system.

Which of the following is TRUE according to the passage?

Read the passage carefully. Choose an option (A, B, C, or D) that best answers each question from to 646 to 650:

1. Millions of people are using cellphones today. In many places, it is actually considered unusual not to use one. In many countries, cellphones are very popular with young people. They find that the phones are more than a means of communication - having a mobile phone shows that they are cool and connected.

2. The explosion in mobile phone use around the world has made some health professionals worried. Some doctors are concerned that in the future many people may suffer health problems from the use of mobile phones. In England, there has been a serious debate about this issue. Mobile phone companies are worried about the negative publicity of such ideas. They say that there is no proof that mobile phones are bad for your health.

3. On the other hand, medical studies have shown changes in the brain cells of some people who use mobile phones. Signs of change in the tissues of the brain and head can be detected with modern scanning equipment. In one case, a traveling salesman had to retire at young age because of serious memory loss. He couldn't remember even simple tasks. He would often forget the name of his own son. This man used to talk on his mobile phone for about six hours a day, every day of his working week, for a couple of years. His family doctor blamed his mobile phone use, but his employer's doctor didn't  agree.

4. What is it that makes mobile phones potentially harmful? The answer is radiation. High-tech machines can detect very small amounts of radiation from mobile phones. Mobile phone companies agree that there is some radiation, but they say the amount is too small to worry about.

5. As the discussion about their safety continues, it appears that it's best to use mobile phones less often. Use your regular phone if you want to talk for a long time. Use your mobile phone only when you really need it. Mobile phones can be very useful and convenient, especially in emergencies. In the future, mobile phones may have a warning label that says they are bad for your health. So for now, it's wise not to use your mobile phone too often.

What could be the most suitable title for the passage?

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 sentences.

Some kinds of fish live in fresh water. Others live in sea water.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40.

Mountain Lions Amid Wildfires: A Struggle for Survival

Beth Pratt, the California director for the National Wildlife Federation, has spent her career protecting Los Angeles’ mountain lions. These top predators live in a rocky area surrounded by fancy houses and many roads. When wildfires destroy vast stretches of open land, the survival options for these animals become critically limited. “This is the LA area—these mountain lions can’t just move into the Kardashians’ backyard,” Pratt says, her voice filled with concern for the animals in such a difficult situation.

(I) The chaparral vegetation, covering about 10% of California, is one of the world’s most flammable ecosystems. (II) In Los Angeles, suburban sprawl intrudes on these areas, blocking wildlife escape routes. (III)Fires strip the land of food and shelter, transforming vibrant ecosystems into barren landscapes. (IV) Pratt highlights the urgency of the situation, explaining how areas that once supported life are now “taken out of commission,” leaving many species to starve or struggle for survival.

The consequences extend beyond wildlife. Wildfires have caused devastating human losses, with 88,000 people evacuated and a rising death toll of 25. Meanwhile, the non-human world suffers equally, particularly endangered species with limited ranges. Red-legged frogs, reintroduced into Santa Monica streams in 2014, are among the most affected, with their habitats repeatedly destroyed. The Woolsey Fire of 2018 was followed by mudslides that wiped out much of the region's delicate ecosystem, and scientists fear similar outcomes this time. California newts, reptiles, and snakes are also at high risk, while mammals and birds, although more likely to escape, face challenges in finding food and shelter as the ecosystem bounces back.

Despite the devastation, hope remains. The chaparral is a fire-adapted ecosystem, and life often endures beneath the soil. Seeds can survive and germinate quickly, with grasses sprouting weeks after the first rain. Shrubs may take up to a decade to recover, depending on rainfall. Prof. Stefan Doerr, an expert on wildfires, emphasizes the resilience of this landscape, noting its evolutionary adaptation to high-intensity fires occurring every 30 to 100 years. While the aftermath looks bleak, these fires play a role in maintaining biodiversity, offering a glimmer of hope for recovery.

According to the passage, which of the following statements is TRUE?

Phiên mã ngược là quá trình tổng hợp DNA dựa trên khuôn mẫu RNA. Quá trình này được xúc tác bởi một loại enzyme đặc biệt gọi là enzyme phiên mã ngược (RT: reverse transcriptase). Enzyme này có cả hoạt tính DNA polymerase và hoạt tính RNase H. Cũng giống như DNA polymerase trong quá trình tái bản DNA, enzyme phiên mã ngược đòi hỏi phải có primer (mồi) đặc biệt để tổng hợp nên DNA mới.

Enzyme phiên mã ngược được phát hiện lần đầu tiên ở retrovirus. Sau khi các retrovirus đi vào tế bào vật chủ, genome của RNA của nó sẽ được phiên mã ngược thành DNA sợi đôi, rồi tích hợp vào DNA của vật chủ.

Tại sao hiện tượng phiên mã ngược thường được phát hiện ở retrovirus?

Trong quá trình chuẩn độ \({\rm{F}}{{\rm{e}}^{2 + }}\left( {} \right.\) hay \(\left. {{{\left[ {{\rm{Fe}}{{\left( {{\rm{O}}{{\rm{H}}_2}} \right)}_6}} \right]}^{2 + }}} \right)\) bằng dung dịch thuốc tím thì chất đóng vai trò chất oxi hoá là

Trong những tình huống nào sau đây, máy tính thực thi công việc tốt hơn con người?

Nguyên tố X có Z = 12. Khi nguyên tử nguyên tố X nhường đi 2 electron thì tạo thành ion X²⁺ có cấu hình electron là

Auxin chủ yếu sinh ra ở bộ phận nào?

a. Omar: That's called the urban heat island effect. Cities with lots of buildings and cars get very hot.

b. Tuan: It's so hot today, but not because of the sun. It's because of the buildings.

c. Tuan: I guess having more parks and trees in cities would help.

Read the following passage about Reducing Electronic Waste and mark the letter A, B, C or D on your answer sheet to indicate the option that best fits each of the numbered blanks from 18 to 22.

In today's hyper-connected world, our constant need for the newest electronic devices has led to a growing environmental crisis. Electronic waste, or e-waste, is one of the fastest-growing waste streams globally, with millions of tons discarded annually. A digital detox, (18)_________, can be an effective environmental practice that helps address this issue.

(19)_________, the current e-waste crisis might have been avoided. The devices that we carelessly discard often contain valuable materials that could be recycled and harmful components that contaminate soil and water. Many consumers replace functioning smartphones and laptops simply because newer models are available, not realizing the environmental impact of their decisions. The manufacturing process of new electronics requires significant resources and energy; (20)_________.

Practicing digital detox not only improves mental health but also decreases the demand for new products. (21)_________; however, if consumer demand decreases, production might slow down as well. Individuals who commit to using their devices for longer periods contribute significantly to waste reduction, and they often discover that older models fulfill their needs perfectly well.

The electronic waste problem requires both individual action and systemic change. We can create a world embracing sustainable principles, (22)_________, through our participation in digital detox practices and mindful consumption.

Hoocmôn sinh trưởng GH được sinh ra ở bộ phận nào?

Vật nào dưới đây chịu biến dạng kéo?